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1. A 7 National Instruments Hardware A 8 What Driver Are You Using 0 0000 cece eee nes A 8 Is Your Hardware Functioning Properly A 10 Sound Cards a ee iena ak Ne RS AS Saito Blew os A 11 Microphone and Sound Card Types 00000 ees A 14 Testing with a Microphone 0 0 e cece eee A 15 Testing witha CD Player 0 0 eee A 15 Running in Full Duplex Mode 00 0005 A 17 ix x Contents Other Things to Try 0 0 0 0 A 18 Registering the Hardware Driver Adaptor A 18 Contacting The MathWorks 0 000 e eens A 19 Managing Your Memory Resources B Memory Allocation 00 B 2 How Much Memory Do You Need B 3 Example Managing Memory Resources B 4 Glossary Index Preface This chapter provides a brief overview of the Data Acquisition Toolbox as well as information about this documentation set The sections are as follows What Is the Data Acquisition The toolbox and the kinds of tasks it can perform Toolbox p xii Related Products p xiii MathWorks products related to this toolbox Using This Guide p xiv An overview of this guide Installation Information How to determine whether the toolbox is installed on your system p xvii Typographical Conventions Typographical conventions that this gu
2. 10 2 Functions By Category 0 0 0 cece eens 10 3 Functions Alphabetical List 10 7 Base Property Reference 11 Getting Command Line Property Help 11 2 Properties By Category 0 0 c cee eee 11 3 Analog Input Properties 0 cece eens 11 3 Analog Output Properties 0 0 0 0 eens 11 8 Digital I O Properties 0 0 cc cee eens 11 12 Properties Alphabetical List 11 14 Device Specific Property Reference 12 Getting Command Line Property Help 12 2 Properties By Vendor 0 0 0 e eee eens 12 3 Agilent Technologies Properties 00 cee eee 12 3 Keithley Properties ii 3 0 cae oe ne iio Swen ee 12 4 Measurement Computing Properties 06 12 5 National Instruments Properties 0 0000 aes 12 5 Parallel Port Properties 00 c cece eens 12 6 Sound Card Properties 000 eee ees 12 6 Properties Alphabetical List 12 7 Troubleshooting Your Hardware A Agilent Technologies Hardware A 2 What Driver Are You Using 0 000 cee nes A 2 Is Your Hardware Functioning Properly A 3 Measurement Computing Hardware A 5 What Driver Are You Using 0 0000 ccc eens A 5 Is Your Hardware Functioning Properly
3. Click Help to view property descriptions OK Cancel Help 9 13 9 softscope The Data Acquisition Oscilloscope Triggering the Oscilloscope To display acquired data in the Oscilloscope you must click the Trigger button You control how the data acquisition is initiated by specifying the acquisition type and the trigger type in the Trigger panel Acquisition Types The Oscilloscope supports three acquisition types which you select from the Acquire menu One Shot Acquire the specified number of samples once e Continuous Continuously acquire the specified number of samples e Sequence Continuously acquire the specified number of samples and use the dependent trigger type each time For each acquisition type you can either fill the display with data or you can acquire a specific number of samples Additionally the specified trigger type see below determines how the acquisition is initiated Trigger Types The Oscilloscope supports two trigger types which you select from the Type menu e Dependent Data acquisition depends on the data You define this dependency by specifying the hardware channel trigger condition trigger condition value and whether pretrigger data is acquired Note that you can specify a dependent trigger for only one channel at a time and this channel initiates data acquisition for all other channels defined for the Oscilloscope e Independent Data acquisi
4. Interactive functions and data Data Acquisition Toolbox M file functions Data acquisition engine Hardware driver adaptors Property values data and events Hardware driver Property values data and events Sensors Hardware gt Actuators 2 2 Toolbox Components The preceding diagram illustrates how information flows from component to component Information consists of e Property values You can control the behavior of your data acquisition application by configuring property values In general you can think of a property as a characteristic of the toolbox or of the hardware driver that can be manipulated to suit your needs Data You can acquire data from a sensor connected to an analog input subsystem and store it in MATLAB or output data from MATLAB to an actuator connected to an analog output subsystem Additionally you can transfer values 1 s and 0 s between MATLAB and a digital I O subsystem Events An event occurs at a particular time after a condition is met and might result in one or more callbacks that you specify Events can be generated only after you configure the associated properties Some of the ways you can use events include initiating analysis after a predetermined amount of data is acquired or displaying a message to the MATLAB workspace
5. Event Type Type Field Value Data Field Value Run time error Error AbsTime RelSample String Start Start AbsTime RelSample Stop Stop AbsTime RelSample Events and Callbacks Table 6 10 Analog Output Event Information Stored in EventLog Continued Event Type Type Field Value Data Field Value Trigger Trigger AbsTime RelSample Samples output events and timer events are not stored in EventLog Note Unless a run time error occurs EventLog records a start event a trigger event and stop event for each data acquisition session The Data field values are described below The AbsTime Field AbsTime is used by all analog output events stored in EventLog to indicate the absolute time the event occurred The absolute time is returned using the MATLAB clock format day month year hour minute second The RelSample Field Re1Samp1e is used by all events stored in EventLog to indicate the sample number that was output when the event occurred RelSamp1e is 0 for the start event and for the first trigger event regardless of the trigger type RelSample is NaN for any event that occurs before the trigger executes The String Field String is used by the run time error event to store the descriptive message that is generated when a run time error occurs This message is also displayed at the MATLAB command line 6 29 6 Analog Output 6 30 Example Retrieving Event Information Suppose you want to exami
6. 7 3 7 Digital Input Output Adding Lines to a Digital 1 O Object After creating the digital I O DIO object you must add lines to it As shown by the figure in Adding Channels or Lines on page 3 8 you can think of a device object as a container for lines The collection of lines contained by the DIO object is referred to as a line group A line group consists of a mapping between hardware line IDs and MATLAB indices see below When adding lines to a DIO object you must follow these rules e The lines must reside on the same hardware device You cannot add lines from different devices or from different subsystems on the same device e You can add a line only once to a given digital I O object However a line can be added to as many different digital I O objects as you desire e You can add lines that reside on different ports to a given digital I O object You add lines to a digital I O object with the addline function addline requires the device object at least one hardware line ID and the direction input or output of each added line as input arguments You can optionally specify port IDs descriptive line names and an output argument For example to add eight output lines from port 0 to the device object dio created in the preceding section hwlines addline dio 0 7 out The output argument hwlines is a line object that reflects the line group contained by dio You can display the class of hwlines wi
7. You Data Acquisition Toolbox and MATLAB NI DAQ National Instruments AT MIO 16E 1 board The diagram illustrates that you supply information to the hardware and you receive information from the hardware T introduction to Data Acquisition Driver Software For data acquisition device there is associated driver software that you must use Driver software allows you to access and control the capabilities of your hardware Among other things basic driver software allows you to e Bring data on to and get data off of the board e Control the rate at which data is acquired e Integrate the data acquisition hardware with computer resources such as processor interrupts DMA and memory e Integrate the data acquisition hardware with signal conditioning hardware e Access multiple subsystems on a given data acquisition board e Access multiple data acquisition boards Application Software Application software provides a convenient front end to the driver software Basic application software allows you to e Report relevant information such as the number of samples acquired e Generate events e Manage the data stored in computer memory e Condition a signal e Plot acquired data With some application software you can also perform analysis on the data MATLAB and the Data Acquisition Toolbox provide you with these capabilities and more The Analog Input Subsystem The Analog Input Subsystem Many data acquisition hardwa
8. The saved structure is shown below where t0 is the time of the first stored sample Note that the time is negative because pretrigger data was acquired co c0 horizontalScale 0 0050 horizontal0Offset 0 verticalScale 2 5730 verticalOffset 0 data 1000x1 double tO 0 0200 samplerate 5000 Measurements You export measurement data with the Measurement Exporter GUI which you open by selecting the File gt Export gt Measurement menu item The GUI shown below is configured to export the peak to peak and absolute value measurements for CHO to the workspace The maximum number of measurements exported depends on the BufferSize property value for each measurement type The variable name for the peak to peak measurement is mO and the variable name for the absolute value measurement is m1 Measurement Exporter xj Save the measurement data to the workspace Channel me Type Variable Name fw CHo Pak j Save the data for both measurements M cHo labs to the variable names mO and m1 Expor Close Help 9 24 Saving and Loading the Oscilloscope Configuration Saving and Loading the Oscilloscope Configuration You can save the Oscilloscope configuration to a softscope file Softscope files are text based files that contain this information e The hardware configuration e The property values e The screen position You create a softscope file by selecting Save or Save As from the File menu Th
9. 5 Clean up When you no longer need AIVoice you should remove it from memory and from the MATLAB workspace delete AIVoice clear AIVoice 5 23 5 Doing More with Analog Input Note that when using software triggers you must specify the TriggerType value before the TriggerCondition value The output from this example is shown below Voice Activation 0 3 T T T 0 2 f 4 Signal Level Volts 1 1 1 0 005 0 01 0 015 0 02 0 025 Time sec The first logged sample has a signal level value of at least 0 2 volt and this value corresponds to time 0 Note that after you issue the getdata function 87 200 samples remain in the engine AlVoice SamplesAvailable ans 87200 5 24 Configuring Analog Input Triggers Executing the Trigger For an analog input trigger to occur you must follow these steps 1 Configure the appropriate trigger properties 2 Issue the start function 3 Issue the trigger function if TriggerType value is Manual Once the trigger occurs data logging is initiated The device object and hardware device stop executing when the requested samples are acquired a run time error occurs or you issue the stop function Note After a trigger occurs the number of samples specified by SamplesPerTrigger is acquired for each channel group member before the next trigger can occur Trigger Delays Trigger delays allow you to control exactly when data is logged afte
10. Access whether the property is read write or read only Read write property values can be returned with the get command and configured with the set command Read only property values can be returned with the get command but cannot be configured with the set command Data type the property data type The supported data types include action function double string Channel Line and any Read only when running whether a property value can be configured when the device object is running e Valid property values including the default value When property values are given by a predefined list the default value is usually indicated by curly braces Default values for some properties are calculated by the data acquisition engine while others are determined by the hardware driver If there are device specific values they are listed separately e An example using the property e Related properties and functions BufferingConfig Purpose Description Characteristics Specify the per channel allocated memory Buf feringConfig is a two element vector that specifies the per channel allocated memory The first element of the vector specifies the block size while the second element of the vector specifies the number of blocks The total allocated memory in bytes is given by block size number of blocks number of channels native data type You can determine the native data type with daqhwinfo You can alloca
11. Analyzing the Data For this example analysis consists of finding the frequency components of the tuning fork and plotting the results To do so the function daqdocfft was created This function calculates the FFT of data and requires the values of SampleRate and SamplesPerTrigger as well as data as inputs f mag daqdocfft data Fs blocksize daqdocfft outputs the frequency and magnitude of data which you can then plot daqdocfft is shown below function f mag daqdocfft data Fs blocksize F MAG DAQDOCFFT X FS BLOCKSIZE calculates the FFT of X using sampling frequency FS and the SamplesPerTrigger provided in BLOCKSIZE X xfft abs fft data Avoid taking the log of 0 index find xfft 0 xfft index 1e 17 mag 20 10g10 xfft mag mag 1 floor blocksize 2 f O length mag 1 Fs blocksize ie tess The results are given below plot f mag grid on ylabel Magnitude dB xlabel Frequency Hz 4 16 Analog Input Examples title Frequency Components of Tuning Fork Frequency Components of Tuning Fork 60 T T T T 40 4 30h 3 4 207 Magnitude dB 1 i 1 ii i 0 500 1000 1500 2000 2500 3000 3500 4000 Frequency Hz The plot shows the fundamental frequency around 440 Hz and the first overtone around 880 Hz A simple way to find actual fundamental frequency is ymax maxindex max mag maxindex
12. Before data can be sent to the analog output hardware you must queue it in the engine Queuing data is managed with the putdata function One column of data is required for each channel contained by the analog output object For example to queue one second of data for each channel contained by the analog output object ao ao analogoutput winsound addchannel ao 1 2 data sin linspace 0 2 pi 500 8000 putdata ao data data Managing Output Data A data source consisting of m samples and n channels is illustrated below dy dye do dye dg d32 dint ding dmn Data source Each column represents a separate output channel Rules for Using putdata Using putdata to queue data in the engine follows these rules e You must queue data in the engine before starting the analog output object e If the value of the RepeatOutput property is greater than 0 then all queued data is automatically requeued until the RepeatOutput value is reached You must configure RepeatOutput before start is issued e While the analog output object is running you can continue to queue data unless RepeatOutput is greater than 0 e You can queue data in the engine until the value specified by the MaxSamplesQueued property is reached or the limitations of your hardware or computer are reached For more information about putdata refer to its reference pages in Chapter 10 Function Reference Rules for Queuing Data D
13. ChannelName DefaultChannel Value HwChannel Index NativeOffset Specify a descriptive channel name Specify the value held by the analog output subsystem Specify the hardware channel ID Indicate the MATLAB index of a hardware channel Indicate the offset to use when converting between the native data format and doubles 11 11 11 bs Property Referenc 11 12 Analog Output Channel Properties Continued NativeScaling Indicate the scaling to use when converting between the native data format and doubles OutputRange Specify the range of the analog output hardware subsystem Parent Indicate the parent device object of a channel Type Indicate a channel Units Specify the engineering units label UnitsRange Specify the range of data as engineering units Digital 1 0 Properties Digital I O base properties are divided into two main categories common properties and line properties Common properties apply to every line contained by the digital I O object while line properties can be configured for individual lines Common Properties The digital I O common properties are given below Digital 1 O Common Properties Line Contain hardware lines added to the device object Name Specify a descriptive name for the device object Running Indicate if the device object is running Tag Specify a device object label TimerFen Specify the M file callback function to execute whenever a
14. Settling time is a function of sampling rate and gain value High rate high gain configurations require longer settling times while low rate low gain configurations require shorter settling times Precision The number of bits used to represent an analog signal determines the precision resolution of the device The more bits provided by your board the more precise your measurement will be A high precision high resolution device divides the input range into more divisions thereby allowing a smaller detectable voltage value A low precision low resolution device divides the input range into fewer divisions thereby increasing the detectable voltage value The overall precision of your data acquisition system is usually determined by the A D converter and is specified by the number of bits used to represent the analog signal Most boards use 12 or 16 bits The precision of your measurement is given by fe number of bits Precision one part in 2 The precision in volts is given by isi f bit Precision voltage range jopumber of bits Making Quality Measurements For example if you are using a 12 bit A D converter configured for a 10 volt range then Precision 10 volts 2 This means that the converter can detect voltage differences at the level of 0 00244 volts 2 44 mV How Are Range Gain and Measurement Precision Related When you configure the input range and gain of your analog input subsystem the end
15. differential inputs 1 23 digital I O object adding lines 7 4 creating 7 2 display summary 7 20 parallel port adaptor 7 3 port types 7 5 properties common 11 12 line 11 13 reading values 7 14 starting 7 18 status evaluation 7 20 Index stopping 7 18 writing values 7 12 digital triggers Agilent hardware AI object 5 38 AO object 6 25 MCC hardware AI 5 40 NI hardware AI object 5 43 AO object 6 24 digital values reading 7 14 writing 7 12 digitalio function 10 51 Direction property 11 28 disk logging 11 47 disp function 10 53 display summary AI object 4 22 AO object 6 14 DIO object 7 20 DMA 1 27 NI hardware 12 35 documentation examples 2 12 dot notation configuring property values 3 18 returning property values 3 17 saving property values to an M file 8 2 DriveAISenseToGround property 12 12 driver Agilent hardware A 2 MCC hardware A 5 NI hardware A 8 E E1432 driver A 2 engine 2 4 extracting data from 5 12 queuing data to 6 16 engineering units AI object 5 55 AO object 6 34 event log AI object 5 48 AO object 6 28 event types data missed AI 5 46 input overrange AI 5 46 run time error AI object 5 46 AO object 6 27 samples acquired AI 5 46 samples output AO 6 27 start AI object 5 47 AO object 6 27 stop AI object 5 47 AO object 6 27 timer AI object 5 47 AO object 6 27 trigger AI object 5 47 AO object 6 28 EventLog property 11 29 events 2 3 AI object 5 45 AO object 6 26 displayin
16. 0 0 0 000 00 cee eee xvii Toolbox Installation 0 ee saa EE eee eens xvii Hardware and Driver Installation 044 xvii Typographical Conventions 0000 00 xviii Introduction to Data Acquisition 1 Anatomy of a Data Acquisition Experiment 1 2 The Data Acquisition System 00000ee 1 3 Data Acquisition Hardware 00 c cece eens 1 5 DENSOPS lt s tests chia wiebtes caused baWie ee tad es ease Pauls Bes 1 7 Signal Conditioning 0 0 eee eens 1 10 The Computer air ere cuatro aka Jeane We a 1 12 Software s biosa nidan eso bee wakes nee sade weal ees 1 12 Contents The Analog Input Subsystem 00005 1 15 Sampling 055 sks iad es ae dh teas ew BO ees wae HERTA 1 15 QUANTIZATION ele eee teen so Bas Blea Be Bee Shas ee es 1 19 Channel Configuration 0 0 0 e cece eee eee 1 23 Transferring Data from Hardware to System Memory 1 26 Making Quality Measurements 0055 1 28 Accuracy and Precision 00 0 c cece cee eens 1 28 Nole scanitae chee eV Rea oe Rae oS RN bee Re oe 1 32 Matching the Sensor Range and A D Converter Range 1 33 How Fast Should a Signal Be Sampled 1 34 Selected Bibliography 0 ccc cece 1 38 Getting Started with the Data Acquisition Toolbox 2 Toolbox Components 0000 c cece eens 2 2 M File Fu
17. Externally control the channel clock AO only Externally control the channel clock This value overrides the ChannelSkew property value AI only Externally control the scan clock This value overrides the SampleRate property value AI only Externally control the channel and scan clocks This value overrides the ChannelSkew and SampleRate property values AI only For an analog output object a ClockSource value of Internal is analogous to a value of Update Sound Cards Internal Properties The internal hardware clock is used ChannelSkew SampleRate 11 25 DataMissedFcn Purpose Description Characteristics Values See Also 11 26 Specify the M file callback function to execute when data is missed A data missed event is generated immediately after acquired data is missed This event executes the callback function specified for DataMissedFcn The default value for DataMissedFcn is daqcallback which displays the event type and the device object name In most cases data is missed because e The engine cannot keep up with the rate of acquisition e The driver wrote new data into the hardware s FIFO buffer before the previously acquired data was read You can usually avoid this problem by increasing the size of the memory block with the Buf feringConfig property Data missed event information is stored in the Type and Data fields of the EventLog property The Type field value is DataMissed
18. Property Name Description Logging Indicate if data is being logged to memory or to a disk file Running Indicate if the device object is running SamplesAcquired Indicate the number of samples acquired per channel SamplesAvailable Indicate the number of samples available per channel in the data acquisition engine When you issue the start function Running is automatically set to On When the trigger executes Logging is automatically set to On and SamplesAcquired keeps a running count of the total number of samples per channel that have been logged to the engine or a disk file SamplesAvailable tells you how many samples per channel are available to be extracted from the engine with the getdata function 4 21 4 Getting Started with Analog Input 4 22 When the requested number of samples are acquired SamplesAcquired reflects this number and both Running and Logging are automatically set to Off When you extract all the samples from the engine SamplesAvailable is 0 The Display Summary You can invoke the display summary by typing an AI object or a channel object at the MATLAB command line or by excluding the semicolon when e Creating an AI object e Adding channels e Configuring property values using the dot notation You can also display summary information via the Workspace browser by right clicking a device object and selecting Explore gt Display Summary from the context menu The displayed information re
19. SampleRate 2000 TriggerRepeat 4 SamplesPerTrigger 10000 You can use waittilstop to block the MATLAB command line until all the requested data is acquired Because the expected acquisition time is 25 seconds the waittime argument is 26 If the acquisition does not complete within this time then a timeout occurs start ai waittilstop ai 26 Properties EventLog Running StopFcn Timeout 10 109 waittilstop 10 110 Base Property Reference This chapter describes all toolbox base properties Base properties apply to all supported hardware subsystems of a given type analog input analog output etc For example the SampleRate property is supported for all analog input subsystems regardless of the vendor The sections are as follows Getting Command Line How to use the daqhelp and propinfo functions to return property help Property Help p 11 2 Properties By Category Contains a series of tables that group base properties by category p 11 3 Properties Alphabetical Lists all the base properties alphabetically List p 11 14 11 bs Property Referenc Getting Command Line Property Help To get command line property help you should use the daqhelp function For example to get help for the SampleRate property daqhelp SampleRate Note You can use daghelp without creating a device object You can also get property characteristics such as the default property value using the p
20. The Data Acquisition System Filtering Filtering removes unwanted noise from the signal of interest A noise filter is used on slowly varying signals such as temperature to attenuate higher frequency signals that can reduce the accuracy of your measurement Rapidly varying signals such as vibration often require a different type of filter known as an antialiasing filter An antialiasing filter removes undesirable higher frequencies that might lead to erroneous measurements Electrical Isolation If the signal of interest contains high voltage transients that could damage the computer then the sensor signals should be electrically isolated from the computer for safety purposes You can also use electrical isolation to make sure that the readings from the data acquisition hardware are not affected by differences in ground potentials For example when the hardware device and the sensor signal are each referenced to ground problems occur if there is a potential difference between the two grounds This difference can lead to a ground loop which might lead to erroneous measurements Using electrically isolated signal conditioning modules eliminates the ground loop and ensures that the signals are accurately represented Multiplexing A common technique for measuring several signals with a single measuring device is multiplexing Signal conditioning devices for analog signals often provide multiplexing for use with slowly changing signal
21. This example illustrates how to read and write digital values using a line configurable subsystem With line configurable subsystems you can transfer values on a line by line basis You can run this example by typing daqdoc7_1 at the MATLAB command line 1 Create a device object Create the digital I O object dio for a National Instruments board The installed adaptors and hardware IDs are found with daqhwinfo dio digitalio nidaq 1 2 Add lines Add eight output lines from port 0 line configurable addline dio 0 7 out 3 Read and write values Write a value of 13 to the first four lines as a decimal number and as a binary vector and read back the values data 13 putvalue dio Line 1 4 data vali getvalue dio bvdata dec2binvec data putvalue dio Line 1 4 bvdata val2 getvalue dio 7 15 7 Digital Input Output 7 16 Write a value of 3 to the last four lines as a decimal number and as a binary vector and read back the values data 3 putvalue dio Line 5 8 data val3 getvalue dio Line 5 8 bvdata dec2binvec data 4 putvalue dio Line 5 8 bvdata val4 getvalue dio Line 5 8 Read values from the last four lines but switch the most significant bit MSB and the least significant bit LSB val5 getvalue dio Line 8 1 5 Clean up When you no longer need dio you should remove it from memory and from the MATLAB workspace delete dio clear dio Ge
22. You can also display summary information via the Workspace browser by right clicking a toolbox object and selecting Explore gt Display Summary from the context menu The information displayed reflects many of the basic setup properties described in Configuring Analog Output Properties on page 6 5 and is designed so you can quickly evaluate the status of your data acquisition session The display is divided into two main sections general summary information and channel summary information General Summary Information The general display summary includes the device object type and the hardware device name followed by this information e Output parameters The sampling rate e Trigger parameters The trigger type e The engine status Whether the engine is sending data waiting to start or waiting to trigger The total time required to output the queued data The number of samples queued by putdata The number of samples sent to the hardware device Getting Started with Analog Output General display summary Channel display _ summary Channel Summary Information The channel display summary includes property values associated with e The hardware channel mapping e The channel name e The engineering units The display summary shown below is for the example given in Outputting Data with a Sound Card on page 6 10 prior to issuing the start function Display Summary of Analog Output AO Object Usin
23. analoginput winsound chans addchannel AI 1 2 AI SampleRate 44100 AI Channel 1 ChannelName CH1 chans 10 54 flushdata Purpose Syntax Arguments Description Example Remove data from the data acquisition engine flushdata obj flushdata obj mode obj An analog input object or array of analog input objects mode Specifies how much data is removed from the engine flushdata obj removes all data from the data acquisition engine and resets the SamplesAvailable property to zero flushdata obj mode removes data from the data acquisition engine depending on the value of mode If mode is a11 all data is removed from the engine and the SamplesAvailable property is set to 0 This is the same as flushdata obj If mode is triggers then data is removed from the engine only when the data corresponds to an integral number of triggers triggers is a valid choice only when the TriggerRepeat property is greater than 0 and the SamplesPerTrigger property is not inf Create the analog input object ai for a National Instruments board and add hardware channels 0 7 to it ai analoginput nidaq 1 addchannel ai 0 7 A two second acquisition is configured and the device object is executed set ai SampleRate 2000 duration 2 ActualRate get ai SampleRate set ai SamplesPerTrigger ActualRate duration start ai Four thousand samples will be acquired for each channel group member
24. converts obj to the equivalent MATLAB code using the set syntax and saves the code to file all specifies that all properties are written to file obj2mfile obj file syntax all converts obj including all of obj s properties to the equivalent MATLAB code using syntax and saves the code to file obj2mfile Remarks Example If the UserData property is not empty or if any of the callback properties are set to a cell array of values or a function handle then the data stored in those properties is written to a MAT file when when the object is converted and saved The MAT file has the same name as the M file containing the object code see the example below You can recreate the saved device objects by typing the name of the M file at the command line You can also recreate channels or lines by typing the name of the M file with a device object as the only input Create the analog input object ai for a sound card add two channels and set values for several properties ai analoginput winsound addchannel ai 1 2 set ai Tag myai TriggerRepeat 4 set ai StartFen mycallback 2 magic 10 The following command writes MATLAB code to the files myai m and myai mat obj2mfile ai myai m dot myai m contains code that recreates the analog input code shown above using the dot notation for all properties that have their default values changed Because StartFcn is set to a cell array of values this propert
25. d1 t1 getdata AIVoice d2 t2 getdata AIVoice Plot the data for both triggers subplot 211 plot t1 d1 grid on hold on axis t1 1 0 05 t1i end 0 05 0 8 0 8 xlabel Time sec ylabel Signal level Volts title Voice Activation First Trigger subplot 212 plot t2 d2 grid on axis t2 1 0 05 t2 end 0 05 0 8 0 8 xlabel Time sec ylabel Signal level Volts title Voice Activation Second Trigger Make sure AlVoice has stopped running before cleaning up the workspace waittilstop AIVoice 2 5 Clean up When you no longer need AIVoice you should remove it from memory and from the MATLAB workspace delete AIVoice clear AIVoice 5 31 5 Doing More with Analog Input 5 32 The data acquired for both triggers is shown below Voice Activation First Trigger Signal level Volts ooo mo e O T T T 2 o ee ON G T 0 6 F 4 0 8 i fi i i i f Time sec Voice Activation Second Trigger Signal level Volts ooo YN A O T T T 2 o A NM O T o o o o 0 5 0 6 0 7 0 8 0 9 1 Time sec As described in Extracting Data from the Engine on page 5 12 if you do not specify the amount of data to extract from the engine with getdata then the amount of data returned is given by the SamplesPerTrigger property You can return data from multiple triggers with one call to getdata by specifying the appropriate number of sam
26. e You select certain property values For example if the samples to acquire per trigger are significantly less than the FIFO buffer of your hardware e You acquire data at the limits of your hardware your computer or the toolbox In particular if you are acquiring data at very high sampling rates then the allocated memory must be carefully evaluated to guarantee that samples are not lost You are free to override the memory allocation rules used by the engine and manually change the block size and number of blocks provided the device object is not running However you should do so only after careful consideration as system performance might be adversely affected which can result in lost data You can manage memory resources using the BufferingConfig property and the daqmem function With Buf feringConfig you can configure and return the block size and number of blocks used by a device object With daqmem you can return the current state of the memory resources used by a device object and configure the maximum memory that one or more device objects can use How Much Memory Do You Need How Much Memory Do You Need The memory in bytes required for data storage depends on these factors e The number of hardware channels you use e The number of samples you need to store in the engine e The data type size of each sample The memory required for data storage is given by the formula memory required samples stored x chann
27. out daghwinfo winsound out ObjectConstructorName ans analoginput winsound 0O analogoutput winsound O Create the analog input object ai for a sound card To display the input ranges for ai ai analoginput winsound out daqhwinfo ai out InputRanges ans 1 1 To display the minimum and maximum sampling rates for ai out daqhwinfo ai MinSampleRate MaxSampleRate out 8000 44100 daqmem Purpose Syntax Arguments Description Allocate or display memory resources out daqmem out daqmem ob j daqmem obj maxmem obj A device object or array of device objects maxmem The amount of memory to allocate out A structure containing information about memory resources out daqmem returns the structure out which contains several fields describing the memory resources associated with your platform and the Data Acquisition Toolbox The fields are described below Field Description MemoryLoad Specifies a number between 0 and 100 that gives a general idea of current memory utilization 0 indicates no memory use and 100 indicates full memory use TotalPhys Indicates the total number of bytes of physical memory AvailPhys Indicates the number of bytes of physical memory available TotalPageFile Indicates the total number of bytes that can be stored in the paging file Note that this number does not represent the actual physical size of the paging file on dis
28. 10 41 daqread Remarks Example 10 42 daqinfo daqread file info returns the structure daqinfo which contains two fields Obj Info and HwInfo ObjInfo is a structure containing property name property value pairs and HwInfo is a structure containing hardware information The entire event log is returned to daqinfo ObjInfo EventLog More About daq Files e The format used by daqread to return data relative time absolute time and event information is identical to the format used by the getdata function e If data from multiple triggers is read then the size of the resulting data array is increased by the number of triggers issued because each trigger is separated by a NaN e Obj Info EventLog always contains the entire event log regardless of the value specified by Samples Time or Triggers e The UserData property value is not restored when you return device object Obj Info information e Data Acquisition Toolbox daq files are created by specifying a value for the LogFileName property or accepting the default value and configuring the LoggingMode property to Disk or Disk amp Memory Suppose you configure the analog input object ai for a National Instruments board as shown below The object acquires one second of data for four channels and saves the data to the output file data daq ai analoginput nidaq 1 chans addchannel ai 0 3 set ai SampleRate 1000 ActualRate get ai SampleRat
29. 11 75 StartFcn Purpose Description Characteristics Values See Also 11 76 Specify the M file callback function to execute just before the device object starts running A start event is generated immediately after the start function is issued This event executes the callback function specified for StartFcn When the callback function has finished executing Running is automatically set to On and the device object and hardware device begin executing Note that the device object is not started if an error occurs while executing the callback function Start event information is stored in the Type and Data fields of the EventLog property The Type field value is Start The Data field values are given below Data Field Value Description AbsTime The absolute time as a clock vector the event occurred RelSample The acquired AI or output AO sample number when the event occurred Usage AI AO Common Access Read write Data type String Read only No when running The default value is an empty string Functions start Properties EventLog Running StopFcn Purpose Description Characteristics Values Specify the M file callback function to execute just after the device object stops running A stop event is generated immediately after the device object and hardware device stop executing This occurs when e A stop function is issued e For analog input AI objects the requested
30. 76 29u CHO 7 4850Vidiv CH1 5 0Vidiv 10 0msidiv On Trigger Display data tips by placing the Click the Trigger button to begin mouse cursor over the trace streaming data into the display The display area contains this information e Labels and markers for each trace For this example the traces are labeled CHO and CH1 e Labels for the vertical units for each trace and a label for the horizontal units for the display When the acquisition is not running you can display data tips by moving the mouse cursor over the trace The data tip is indicated by a red circle and displays the value of the trace at the selected point If you press the Control key while the cursor is over the trace the difference between the first data tip and the last data tip is displayed 9 4 Displaying Channels Creating Additional Displays To add additional displays to the Oscilloscope use the Scope pane of the Scope Editor GUI To open this GUI select Scope from the Edit menu As shown below the new display is named display2 x Scope Scope Properties Define a new display Label Jdisplay2 Specify a unique display label an gt Click the Add button to include Defined scope components the new display in the table Type M Channel Channel Scaling O Measurement Measurements M Trigger Triggers M Display display1 Delete Click the OK or Apply button to includ
31. 8 1 fi i i i i i J 0 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 1 Time sec 1 36 Making Quality Measurements As shown in the top figure the low sampling rate produces a sampled signal that appears to be a triangular waveform As shown in the bottom figure a higher fidelity sampled signal is produced when the sampling rate is higher In the latter case the sampled signal actually looks like a sine wave How Can Aliasing be Eliminated The primary considerations involved in antialiasing are the sampling rate of the A D converter and the frequencies present in the sampled data To eliminate aliasing you must e Establish the useful bandwidth of the measurement e Select a sensor with sufficient bandwidth e Select a low pass anti aliasing analog filter that can eliminate all frequencies exceeding this bandwidth e Sample the data at a rate at least twice that of the filter s upper cutoff frequency 1 37 T introduction to Data Acquisition 1 38 Selected Bibliography Transducer Interfacing Handbook A Guide to Analog Signal Conditioning edited by Daniel H Sheingold Analog Devices Inc Norwood Massachusetts 1980 Bentley John P Principles of Measurement Systems Second Edition Longman Scientific and Technical Harlow Essex UK 1988 Bevington Philip R Data Reduction and Error Analysis for the Physical Sciences McGraw Hill New York NY 1969 Carr Joseph J Sensors Prompt Publicat
32. A D T T N Amplitude 0 2 0 4 0 6 0 8 1 L L i i L L 0 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 1 Time sec Sample period In a real world data acquisition environment you might need to condition the signal by filtering out the high frequency components 1 35 T introduction to Data Acquisition Even though the samples appear to represent a sine wave with a frequency of one fourth the sampling rate the actual signal could be any sine wave with a frequency of n 0 25 x Sampling rate where n is zero or any positive integer For this example the actual signal could be at a frequency of 3 Hz 5 Hz 7 Hz 9 Hz and so on The relationship 0 25 x Sampling rate is called the alias of a signal that may be at another frequency In other words aliasing occurs when one frequency assumes the identity of another frequency If you sample the input signal at least twice as fast as the highest frequency component then that signal might be uniquely characterized but this rate would not mimic the waveform very closely As shown below to get an accurate picture of the waveform you need a sampling rate of roughly 10 to 20 times the highest frequency 1p 8 0 5 oO ne pe 0 a E lt 0 5 f L 1 L L L L L L L L J 0 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 1 Time sec ti 2 8 0 5 g z OP 4 E lt 0 5 s
33. AI only For a given hardware device additional trigger types might be available Some trigger types require trigger conditions and trigger condition values Trigger conditions are specified with the TriggerCondition property while trigger condition values are specified with the TriggerConditionValue property When a trigger occurs for an analog input object data logging is initiated and the Logging property is automatically set to On When a trigger occurs for an analog output object data sending is initiated and the Sending property is automatically set to On Characteristics Usage AI AO Common Access Read write Data type String Read only Yes when running Values All Supported Hardware Immediate The trigger executes immediately after start is issued Pretrigger data cannot be captured Manual The trigger executes immediately after the trigger function is issued Software The trigger executes when the associated trigger condition is satisfied Trigger conditions are given by the TriggerCondition property AI only 11 95 TriggerType Agilent Technologies HwDigital The trigger source is an external digital signal AI only Pretrigger data cannot be captured HwAnalog The trigger source is an external analog signal AI only HwDigitalPos The trigger source is the positive edge of an external digital signal AO only HwDigitalNeg The trigger source is the negative edge of an external digital signal A
34. Accurate Accurate For analog input subsystems accuracy is usually limited by calibration errors while precision is usually limited by the A D converter Accuracy and precision are discussed in more detail below Accuracy Accuracy is defined as the agreement between a measured quantity and the true value of that quantity Every component that appears in the analog signal path affects system accuracy and performance The overall system accuracy is given by the component with the worst accuracy 1 29 T introduction to Data Acquisition 1 30 For data acquisition hardware accuracy is often expressed as a percent or a fraction of the least significant bit LSB Under ideal circumstances board accuracy is typically 0 5 LSB Therefore a 12 bit converter has only 11 usable bits Many boards include a programmable gain amplifier which is located just before the converter input To prevent system accuracy from being degraded the accuracy and linearity of the gain must be better than that of the A D converter The specified accuracy of a board is also affected by the sampling rate and the settling time of the amplifier The settling time is defined as the time required for the instrumentation amplifier to settle to a specified accuracy To maintain full accuracy the amplifier output must settle to a level given by the magnitude of 0 5 LSB before the next conversion and is on the order of several tenths of a millisecond for most boards
35. All nonzero binary vector elements are interpreted as a 1 A binary vector binvec is constructed with the least significant bit LSB in the first column and the most significant bit MSB in the last column For example the decimal number 23 is written as the binvec value 1 1 1 0 1 To convert the binvec value 1 1 1 0 1 to a decimal value binvec2dec 1 1 1 0 1 ans 23 Functions dec2binvec 10 23 clear Purpose Syntax Arguments Description Remarks 10 24 Remove device objects from the MATLAB workspace clear obj clear obj Channel index clear obj Line index obj A device object or array of device objects obj Channel index One or more channels contained by obj obj Line index One or more lines contained by obj clear obj removes obj and all associated channels or lines from the MATLAB workspace but not from the data acquisition engine clear obj Channel index removes the specified channels contained by obj from the MATLAB workspace but not from the data acquisition engine clear obj Line index removes the specified lines contained by obj from the MATLAB workspace but not from the data acquisition engine Clearing device objects channels and lines follows these rules e clear does not remove device objects channels or lines from the data acquisition engine Use the delete function for this purpose e If multiple references to a device object exist in the workspace cle
36. Line Line group Line properties Logging Noise Onboard clock A MEX file dynamic link library DLL file that stores the device objects and associated property values that control your data acquisition application controls the synchronization of events and controls the storage of acquired or queued data Channel properties that allow you to linearly scale input or output data An event occurs at a particular time after a condition is met Many event types are automatically generated by the toolbox while others are generated only after you configure specific properties The process of starting the device object and hardware device While an analog input object is executing you can acquire data While an analog output object is executing you can output data The first in first out FIFO memory buffer which is used by data acquisition hardware to temporarily store data A system that can send and receive information simultaneously For sound cards full duplex means that the device can acquire input data via an analog input subsystem while outputting data via an analog output subsystem at the same time The span of input values for which an A D conversion is valid The slowest but most common method to move acquired data from the hardware to system memory Interrupt signals can be generated when one sample is acquired or when multiple samples are acquired A component of a digital I O subsystem that you can read digital
37. Stop Stop AbsTime RelSample Trigger Trigger AbsTime RelSample Channel Trigger Events and Callbacks Samples acquired events and timer events are not stored in EventLog Note Unless a run time error occurs EventLog records a start event trigger event and stop event for each data acquisition session The Data field values are described below The AbsTime Field AbsTime is used by the run time error start stop and trigger events to indicate the absolute time the event occurred The absolute time is returned using the MATLAB clock format day month year hour minute second The Channel Field Channel is used by the input overrange event and the trigger event For the input overrange event Channel indicates the index number of the input channel that experienced an overrange signal For the trigger event Channel indicates the index number for each input channel serving as a trigger source The OverRange Field OverRange is used by the input overrange event and can be On or Off If OverRange is On then the input channel experienced an overrange signal If OverRange is Off then the input channel no longer experienced an overrange signal The RelSample Field Re1Samp1e is used by all events stored in EventLog to indicate the sample number that was acquired when the event occurred RelSamp1e is 0 for the start event and for the first trigger event regardless of the trigger type RelSamp1le is NaN for any event that oc
38. The Data field value is RelSample which is the last sample acquired when the event occurred When a data missed event occurs the analog input object is automatically stopped Usage AI Common Access Read write Data type String Read only No when running The default value is daqcallback Functions daqcallback Properties EventLog DefaultChannelValue Purpose Description Characteristics Values Example See Also Specify the value held by the analog output subsystem DefaultChannelValue specifies the value to write to the analog output AO subsystem when data is finished being output from the engine DefaultChannelValue is used only when OutOfDataMode is set to DefaultValue This property guarantees that a known value is held by the AO subsystem if a run time error occurs Note that sound cards do not have an OutOfDataMode property Usage AO Channel Access Read write Data type Double Read only Yes when running The default value is zero Create the analog output object ao and add two channels to it ao analogoutput nidaq 1 addchannel ao 0 1 You can configure ao so that when it stops outputting data a value of 1 volt is held for both channels ao OutOfDataMode DefaultValue ao Channel DefaultChannelValue 1 0 Properties OutOfDataMode 11 27 Direction Purpose Description Characteristics Values Example See Also 11 28 Specify whether a line is us
39. To extract 1000 samples from the data acquisition engine for each channel data getdata ai 1000 10 55 flushdata You can use flushdata to remove the remaining 3000 samples from the data acquisition engine flushdata ai ai SamplesAvailable ans 0 See Also Functions getdata Properties SamplesAvailable SamplesPerTrigger TriggerRepeat 10 56 get Purpose Syntax Arguments Description Return device object properties out get obj out get obj Channel index out get obj Line index out get obj PropertyName out get obj Channel index PropertyName out get obj Line index PropertyName get obj A device object or array of device objects obj Channel index One or more channels contained by obj obj Line index One or more lines contained by obj PropertyName A property name or a cell array of property names out get obj returns the structure out where each field name is the name of a property of obj and each field contains the value of that property out get obj Channel index returns the structure out where each field name is the name of a channel property of obj and each field contains the value of that property out get obj Line index returns the structure out where each field name is the name of a line property of obj and each field contains the value of that property out get obj PropertyName returns the value of the pr
40. You can also return sample time pairs with getdata For example to extract 500 sample time pairs for each channel contained by ai data time getdata ai 500 time is an m by 1 array containing relative time values for all m samples Time is measured relative to the time the first sample is logged and is measured continuously until the acquisition stops getdata is described in more detail in Chapter 10 Function Reference You can log data to disk with the LoggingMode property You can replay data saved to disk with the daqread function Refer to Logging Information to Disk on page 8 5 for more information about LoggingMode and daqread Stopping the Analog Input Object An analog input object can stop under one of these conditions e You issue the stop function e The requested number of samples is acquired e A run time hardware error occurs e A timeout occurs When the device object stops the Running and Logging properties are automatically set to Off At this point you can reconfigure the device object or immediately issue another start command using the current configuration 4 13 4 Getting Started with Analog Input Analog Input Examples This section illustrates how to perform basic data acquisition tasks using analog input subsystems and the Data Acquisition Toolbox For most data acquisition applications you must follow these basic steps 1 Install and connect the components of your data acq
41. You specify the sampling rate with the SampleRate property The maximum rate at which channels are sampled depends on the type of hardware you are using If you are using simultaneous sample and hold SS H hardware such as a sound card then the maximum sampling rate for each channel is given by the maximum board rate For example suppose you create the analog input object ai for a sound card and configure it for stereo operation If the device has a maximum rate of 48 0 kHz then the maximum sampling rate per channel is 48 0 kHz ai analoginput winsound addchannel ai 1 2 set ai SampleRate 48000 If you are using scanning hardware such as a National Instruments board then the maximum sampling rate your hardware is rated at typically applies for one channel Therefore the maximum sampling rate per channel is given by the formula Maximum board rate Maximum sampling rate per channel Namberof channels scanned For example suppose you create the analog input object ai for a National Instruments board and add 10 channels to it If the device has a maximum rate of 100 kHz then the maximum sampling rate per channel is 10 kHz ai analoginput nidaq 1 set ai InputType SingleEnded addchannel ai 0 9 set ai SampleRate 10000 Typically you can achieve this maximum rate only under ideal conditions In practice the sampling rate depends on several characteristics of the analog input subsystem including the
42. and from the MATLAB workspace delete AO clear AO 6 33 6 Analog Output Linearly Scaling the Data Engineering Units The Data Acquisition Toolbox provides you with a way to linearly scale data as it is being queued in the engine You can associate this scaling with specific engineering units such as volts or Newtons that you might want to apply to your data The properties associated with engineering units and linearly scaling output data are given below Table 6 11 Analog Output Engineering Units Properties Property Name Description OutputRange Specify the range of the analog output hardware subsystem Units Specify the engineering units label UnitsRange Specify the range of data as engineering units For many devices the output range is expressed in terms of the gain and polarity Note You can set the engineering units properties on a per channel basis Therefore you can configure different engineering unit conversions for each hardware channel Linearly scaled output data is given by the formula scaled value original value output range units range The units range is given by the UnitsRange property while the output range is given by the OutputRange property UnitsRange controls the scaling of data when it is queued in the engine with the putdata function OutputRange specifies the gain and polarity of your D A subsystem You should choose an output range that encompasses the output si
43. decrease the block size if SampleRate is increased decreased If BufferingMode is set to Auto and you change the BufferingConfig values then BufferingMode is automatically set to Manual If BufferingMode is set to Manual then you cannot set the number of blocks to a value less than three For most data acquisition applications you should set BufferingMode to Auto and have memory allocated by the engine because this minimizes the chance of an out of memory condition Usage Access Data type Read only when running Auto Manual Functions daqmem Properties Buf feringConfig AI AO Common Read write String Yes Memory is allocated by the data acquisition engine Memory is allocated manually 11 17 Channel Purpose Description Characteristics Values Example 11 18 Contain hardware channels added to a device object Channel is a vector of all the hardware channels contained by an analog input AI or analog output AO object Because a newly created AI or AO object does not contain hardware channels Channel is initially an empty vector The size of Channel increases as channels are added with the addchannel function and decreases as channels are removed using the delete function Channel is used to reference one or more individual channels To reference a channel you must know its MATLAB index which is given by the Index property For example you must use Channel with the appropriate indi
44. function Callback property Channel Channel group A determination of how close a measurement comes to the true value The process of inputting an analog signal from a sensor into an analog input subsystem and then converting the signal into bits that the computer can read A device that converts data output from your computer into a physical variable The interface between the data acquisition engine and the hardware driver The adaptor s main purpose is to update the engine with properties that are unique to the hardware device An analog input subsystem Hardware that converts real world analog input signals into bits that a computer can read This is also referred to as an AI subsystem an A D converter or an ADC Hardware that converts digital data to a real world analog signal This is also referred to as an AO subsystem a D A converter or a DAC The range of frequencies present in the signal being measured You can also think of bandwidth as being related to the rate of change of the signal A slowly varying signal has a low bandwidth while a rapidly varying signal has a high bandwidth A property that applies to all supported hardware subsystems of a given type analog input analog output etc For example the SampleRate property is supported for all analog input subsystems regardless of the vendor An M file function that you construct to suit your specific data acquisition needs If you supply the callba
45. get ai Channel 1 NativeScaling offset get ai Channel 1 NativeOffset data double nativedata scaling offset Functions daqhwinfo dagqread getdata putdata Properties InputRange NativeScaling OutputRange NativeScaling Purpose Description Characteristics Values See Also Indicate the scaling to use when converting between the native data format and doubles NativeScaling along with NativeOffset is used to convert data between the native hardware format and doubles For analog input objects you return native data from the engine with the getdata function Additionally if you log native data to a daq file then you can read back that data using the daqread function The formula for converting from native data to doubles is doubles data native data native scaling native offset For analog output objects you queue native data in the engine with the putdata function The formula for converting from doubles to native data is native data doubles data native scaling native offset You return the native data type of your hardware device with the daqhwinfo function Note that the NativeScaling value for a given channel might change if you change its InputRange AI or OutputRange AO property value You might want to return or queue data in native format to conserve memory and to increase data acquisition or data output speed Usage AI AO Channel Access Read only Data type Doubl
46. or if the standard ports do not use the default memory resources they will not be accessible by the toolbox For more information about the parallel port refer to Parallel Port Characteristics on page 7 7 10 51 digitalio Example See Also 10 52 More About the Hardware Device Identifier When data acquisition devices are installed they are assigned a unique number which identifies the device in software The device identifier is typically assigned automatically and can usually be manually changed using a vendor supplied device configuration utility National Instruments refers to this number as the device number There are two ways you can determine the ID for a particular device e Type daqhwinfo adaptor e Open the vendor supplied device configuration utility Create a digital I O object for a National Instruments device defined as device number 1 DIO digitalio nidaq 1 Create a digital I O object for parallel port LPT1 DIO digitalio parallel LPT1 Functions addline daqhwinfo Properties Name disp Purpose Syntax Arguments Description Remarks Display summary information for device objects channels or lines disp obj disp obj Channel index disp obj Line index obj A device object obj Channel index One or more channels contained by obj obj Line index One or more lines contained by obj disp obj displays summary information for the specified device
47. p 7 12 Generating Timer Events Execute the digital I O object and configure properties to generate p 7 17 timer events Evaluating the Digital I O Return the values of certain properties in a convenient display format Object Status p 7 20 Note that the Data Acquisition Toolbox does not directly support buffered DIO or handshaking latching However you can write your own M code to support this functionality Buffered DIO means that the data is stored in the engine Handshaking allows the DIO subsystem to input or output values after receiving a digital pulse 7 Digital Input Output 7 2 Creating a Digital I O Object You create a digital I O DIO object with the digitalio function digitalio accepts the adaptor name and the hardware device ID as input arguments For parallel ports the device ID is the port label LPT1 LPT2 or LPT3 For data acquisition boards the device ID refers to the number associated with the board when it is installed Note that some vendors refer to the device ID as the device number or the board number Use the daghwinfo function to determine the available adaptors and device IDs Each DIO object is associated with one parallel port or one subsystem For example to create a DIO object associated with a National Instruments board dio digitalio nidaq 1 The digital I O object dio now exists in the MATLAB workspace You can display the class of dio with the whos command whos dio Name
48. specified as a cell array DataFormat Specify the data format as doubles or native TimeFormat Specify the time format as vector or matrix The Samples Time and Triggers properties are mutually exclusive If none of these three properties is specified then all the data is returned Retrieving Event Device Object Channel and Hardware Information You can retrieve event device object channel and hardware information along with data and time information using the syntax shown below data time abstime events daqinfo daqread file P1 V1 P2 V2 events is a structure containing event information associated with the logged data The events retrieved depend on the value of the Samples Time or Triggers property At a minimum the trigger event associated with the selected data is returned The entire event log is returned to events only if Samples Time or Triggers is not specified daqinfo is a structure that stores device object channel and hardware information in two fields Obj Info and HwInfo Obj Info is a structure containing property values for the device object and any channels it contains The property values are returned in the same format as returned by get HwInfo is a structure containing hardware information The hardware information is identical to the information returned by daqhwinfo obj Logging Information to Disk Alternatively you can return only object channel and hardware informatio
49. the source constant level output is disabled If COLA is ON the source constant level output is enabled For the Option 1D4 single channel source the source COLA output is shared with the source sum input Only one of these two sources can be enabled at any one time For prototype Option 1D4 sources only one of the two must be enabled at all times and the default is for the constant level output to be enabled Vendor Usage Access Data Type Read only when running Off On Agilent Technologies AO Channel Read write String Yes The source constant level output is disabled The source constant level output is enabled Coupling Purpose Description Characteristics Values Specify the input coupling mode Coupling can be DC or AC If Coupling is DC the input is connected directly to the amplifier If Coupling is AC a series capacitor is inserted between the input connector and the amplifier For source channels Coupling is generally not used because it is usually not possible to AC couple the output of a source After a hardware reset Coupling is automatically set to DC Vendor Usage Access Data type Read only when running DC AC Agilent Technologies National Instruments AI Channel Read write String Yes The input is connected directly to the amplifier A series capacitor is inserted between the input connector and the amplifier 12 11 DriveAlSenseToGround Pu
50. to create an analog input object associated with a National Instruments board with device ID 1 ai analoginput nidaq 1 The analog input object ai now exists in the MATLAB workspace You can display the class of ai with the whos command whos ai Name Size Bytes Class ai 1x1 1332 analoginput object Grand total is 52 elements using 1332 bytes Once the analog input object is created the properties listed below are automatically assigned values These general purpose properties provide descriptive information about the object based on its class type and adaptor Table 4 1 Descriptive Analog Input Properties Property Name Description Name Specify a descriptive name for the device object Type Indicate the device object type You can display the values of these properties for ai with the get function get ai Name Type ans nidaq1 AI Analog Input Adding Channels to an Analog Input Object Adding Channels to an Analog Input Object After creating the analog input object you must add hardware channels to it As shown by the figure in Adding Channels or Lines on page 3 8 you can think of a device object as a container for channels The collection of channels contained by the device object is referred to as a channel group As described in Mapping Hardware Channel IDs to MATLAB Indices on page 3 9 a channel group consists of a mapping between hardware channel IDs and MATLAB indices s
51. which are stored in the ChannelName property Choosing a unique descriptive name can be a useful way to identify and reference channels For a single call to addchannel you can e Specify one channel name that applies to all channels that are to be added e Specify a different name for each channel to be added If the number of names specified in a single addchannel call is more than one but not equal to the number of channels to be added then an error is returned If a channel is to be referenced by its name then that name must not contain symbols If you are naming a large number of channels then the makenames function might be useful If a channel is not assigned a descriptive name then it must be referenced by index A sound card configured in mono mode is automatically assigned the name Mono while a sound card configured in stereo mode is automatically assigned the names Left for the first channel and Right for the second channel You can addchannel Example change these default channel names when the device object is created or any time after the channel is added National Instruments Suppose you create the analog input object AI1 for a National Instruments board and add the first four hardware channels channels 0 3 to it AI1 analoginput nidaq 1 addchannel AI1 0 3 The channels are automatically assigned the indices 1 4 If you want to add the first four hardware channels to AI1 and assign descriptive names
52. 1 y errors include timeouts and hardware errors Start The start function is issued Stop The device object stops executing Trigger A trigger executes y y Timer events samples available events AI and samples output events AO are not logged Data stores event specific information associated with the event type in several fields For all stored events Data contains the RelSample field which returns the input or output sample number at the time the event occurred For the start stop run time error and trigger events Data contains the AbsTime field which returns the absolute time as a clock vector the event occurred Other event specific fields are included in Data For a description of these fields refer to Events and Callbacks in Chapter 5 for analog input objects Events and Callbacks in Chapter 6 for analog output objects or the appropriate reference pages in this chapter EventLog can store a maximum of 1000 events If this value is exceeded then the most recent 1000 events are stored You can use the showdaqevents function to easily display stored event information 11 29 EventLog Characteristics Values Example See Also 11 30 Usage AI AO Common Access Read only Data type Structure array Read only N A when running Values are automatically added as events occur The default value is an empty structure array Create the analog input object ai and add four channels to it
53. 2 Functions delete makenames Properties ChannelName HwChannel Index addline Purpose Syntax Arguments Description Add hardware lines to a digital I O object lines addline obj hwline direction lines addline obj hwline port direction lines addline obj hwline direction names lines addline obj hwline port direction names obj A digital I O object hwline The numeric IDs of the hardware lines added to the device object Any MATLAB vector syntax can be used direction The line directions can be In or Out and can be specified as a single value or a cell array of values port The numeric IDs of the digital I O port names A descriptive line name or cell array of descriptive line names lines A row vector of lines with the same length as hwline lines addline obj hwline direction adds the hardware lines specified by hwline to the digital I O object obj direction configures the lines for either input or output lines is a row vector of lines lines addline obj hwline port direction adds the hardware lines specified by hwline from the port specified by port to the digital I O object obj lines addline obj hwline direction names adds the hardware lines specified by hwline to the digital I O object obj names is a descriptive line name or cell array of descriptive line names lines addline obj hwline port direction names adds the hardware line
54. 4 ans 1 1 1 0 1 Functions binvec2dec delete Purpose Syntax Arguments Description Remarks Remove device objects channels or lines from the data acquisition engine delete obj delete obj Channel index delete obj Line index obj A device object or array of device objects obj Channel index One or more channels contained by obj obj Line index One or more lines contained by obj delete obj removes the device object specified by obj from the engine If obj contains channels or lines they are removed as well If obj is the last object accessing the driver then the driver and associated adaptor are unloaded delete obj Channel index removes the channels specified by index and contained by obj from the engine As a result the remaining channels might be reindexed delete obj Line index removes the lines specified by index and contained by obj from the engine As a result the remaining lines might be reindexed Deleting device objects channels and lines follows these rules e delete removes device objects channels or lines from the data acquisition engine but not from the MATLAB workspace To remove variables from the workspace use the clear function e If multiple references to a device object exist in the workspace then removing one device object from the engine invalidates the remaining references These remaining references should be cleared from the workspace with the clear fun
55. 7 4 hardware triggers AI object 5 36 AO object 6 24 help 2 20 holding the last output value 12 18 HP E1482 driver A 2 HwChannel property 11 31 HwLine property 11 33 I ID channel 4 3 HwChannel 4 5 device board 4 2 line 7 4 HwLine 7 9 mapping to channels 3 9 port 7 4 immediate trigger AI object 5 22 AO object 6 21 Index property 11 34 indexing channel array 4 5 line array 7 9 initializing the hardware 10 45 InitialTriggerTime property 11 36 input overrange event 5 46 input range 1 21 engineering units 5 56 InputMode property 12 14 InputOverRangeFcn property 11 38 InputRange property 11 39 InputSource property 12 16 InputType property 11 41 InstaCal A 5 hardware configuration 2 17 internal clock 1 22 interrupts 1 26 NI hardware 12 35 invalid device object 3 7 ischannel function 10 65 isdioline function 10 66 isnan function 5 34 isvalid function 10 67 J jitter 1 22 K Keithley hardware properties 12 4 L least significant bit DIO 7 9 length function 10 69 line group 7 4 line names 7 10 line object 7 4 line properties 3 12 Line property 11 43 line configurable device 7 6 LineName 7 10 LineName property 11 44 Index lines 3 8 adding 7 4 descriptive names 7 10 referencing 7 9 load function 10 71 loading device objects MAT file 8 4 M file 8 3 Oscilloscope configuration 9 25 LogFileName property 11 45 logging data to memory 3 22 information to disk AI 8 5 file name specification
56. 8 6 multiple files 8 6 retrieving data with daqread 8 7 Logging property 11 46 LoggingMode property 11 47 LogToDiskMode property 11 48 M makenames function 10 73 managing data acquired 5 8 output 6 16 manual trigger AI object 5 22 AO object 6 21 ManualTriggerHwOn property 11 49 mapping channels to hardware IDs 3 9 MAT file device objects saving to 8 4 properties saving to 8 2 math channels Oscilloscope 9 7 maximum samples queued 11 51 MaxSamplesQueued property 11 51 Measurement and Automation Explorer A 8 hardware configuration 2 17 Measurement Computing hardware channel configuration 5 4 driver A 5 properties 12 5 trigger types AI 5 39 troubleshooting A 5 Measurement Editor GUI Measurement pane 9 18 Measurement Properties pane 9 22 Measurement Exporter GUI 9 24 memory resources B 2 mono mode 4 6 most significant bit DIO 7 9 multifunction boards 1 5 multiple device objects array 3 5 starting 6 37 stopping 6 38 multiplexing 1 11 mux board adding channels 10 16 channel indices 10 74 muxchanidx function 10 74 N Name property 11 52 National Instruments hardware AISENSE 12 12 channel configuration 5 4 data transfer mechanisms 12 35 driver A 8 properties 12 5 trigger types 1 9 Index AI object 5 42 AO object 6 24 troubleshooting A 8 native data getdata 10 59 offset 11 53 putdata 10 82 scaling 11 55 NativeOffset property 11 53 NativeScaling property 11 55 NI DAQ driver A 8 noise 1 32
57. Coupling DeviceName DifferentialIDs Gains ID InputRanges MaxSampleRate MinSampleRate NativeDataType Polarity SampleType SingleEndedIDs SubsystemType TotalChannels VendorDriverDescription VendorDriverVersion winsound 16 AC Coupled AudioPCI Record Q 1 1 44100 8000 int16 Bipolar SimultaneousSample 1 2 AnalogInput 2 Windows Multimedia Driver 5 0 Among other things this information tells you that the minimum sampling rate is 8 kHz the maximum sampling rate is 44 1 kHz and there are two hardware channels that you can add to the analog input object Alternatively you can return hardware information via the Workspace browser by right clicking a device object and selecting Explore gt Display Hardware Info from the context menu 2 19 2 Getting Started with the Data Acquisition Toolbox 2 20 Getting Help The Data Acquisition Toolbox provides you with these help resources e The HTML and PDF versions of this guide and the Quick Reference Guide which are available through the Help browser e M file function help which you can display with the help command because some toolbox functions are overloaded you might need to specify the appropriate pathname as well e The daghelp function e The propinfo function The daghelp Function You can use the daghelp function to e Display command line help for functions and properties e Li
58. Create a device object Create the analog output object AO for a sound card The installed adaptors and hardware IDs are found with daqhwinfo AO analogoutput winsound 2 Add channels Add one channel to AO chan addchannel AO 1 3 Configure property values Define an output time of four seconds assign values to the basic setup properties generate data to be queued and queue the data with one call to putdata duration 4 set AO SampleRate 8000 set AO TriggerType Manual ActualRate get AO SampleRate len ActualRate duration data sin linspace 0 2 pi 500 1len putdata A0O data 6 10 Getting Started with Analog Output 4 Output data Start AO issue a manual trigger and wait for the device object to stop running start AO trigger A0 waittilstop A0 5 5 Clean up When you no longer need AO you should remove it from memory and from the MATLAB workspace delete AO clear AO Outputting Data with a National Instruments Board In this example sine wave data is generated in MATLAB output to the D A converter on a National Instruments board and displayed with an oscilloscope The setup is shown below Data Source D A Converter Scope MATLAB 00000 variable D A i oo0oo0o0 You can run this example by typing daqdoc6_2 at the
59. DLLs loaded by the engine including the adaptor and engine DLL files You should use daqreset to return MATLAB to the known initial state of having no device objects and no data acquisition DLLs loaded in memory When MATLAB is returned to this state the data acquisition hardware is reset Functions clear delete 10 45 daqschool Purpose Syntax Description 10 46 Interface for displaying toolbox tutorials daqschool daqschool launches the Data Acquisition Toolbox Tutorials interface which is shown below Data Acquisition Toolbox Tutorials Bik AnalogInput Analog Output Digital O Common The buttons in this window will launch the Data Acquisition Toolbox demos for analog input objects Intreduction illustrates a basic data acquisition session using an analog input object Channels introduces adding and configuring analog input channels Triggers illustrates how data can be acquired using an immediate manual and software trigger Data Legging illustrates how to configure an analey input object for data legging Introduction Channels Triggers Data Logging Refer to Demos on page 2 18 for a list of demos included with daqschool dec2binvec Purpose Syntax Arguments Description Remarks Example Convert decimal value to binary vector out dec2binvec dec out dec2binvec dec bits dec A decimal value dec must be nonnegative bits Number of bits used t
60. InputRange property This event executes the callback function specified for the InputOverRangeFcn property Overrange detection is enabled only when a callback function is specified for InputOverRangeFcn and the analog input object is running Run time Error Event A run time error event is generated immediately after a run time error occurs Additionally a toolbox error message is automatically displayed to the MATLAB workspace If an error occurs that is not explicitly handled by the toolbox then the hardware specific error message is displayed This event executes the callback function specified for RuntimeErrorFcn The default value for RuntimeErrorFcn is daqcallback which displays the event type the time the event occurred the device object name and the error message Run time errors include hardware errors and timeouts Run time errors do not include configuration errors such as setting an invalid property value Samples Acquired Event A samples acquired event is generated immediately after a predetermined number of samples is acquired This event executes the callback function specified for the SamplesAcquiredFcn property every time the number of samples specified by SamplesAcquiredFcnCount is acquired for each channel group member Events and Callbacks You should use SamplesAcquiredFcn if you must access each sample that is acquired However if you are performing a CPU intensive task with the data then system perfor
61. MIO 16E Series board PFI6 WFTRIG corresponds to pin 5 TTL signal PFI6 WFTRIG D A k MIO 16E Series board Agilent Technologies When using Agilent Technologies hardware there are additional analog output trigger types that you must be aware of digital triggering on a positive edge and digital triggering on a negative edge If TriggerType is HwDigitalPos the trigger source is the positive edge of a digital signal If TriggerType is HwDigitalNeg the trigger source is the negative edge of a digital signal In both cases the digital signal is an external TTL signal that is input directly into the hardware device The example below illustrates how to configure such a trigger ao analogoutput hpe1432 8 addchannel ao 1 set ao TriggerType HwDigitalPos With this trigger configuration ao will not start outputting data until the TTL signal is detected by the hardware 6 25 6 Analog Output Events and Callbacks 6 26 You can enhance the power and flexibility of your analog output application by utilizing events An event occurs at a particular time after a condition is met and might result in one or more callbacks While the analog output object is running you can use events to display a message display data analyze data and so on Callbacks are controlled through callback properties and callback functions All event types hav
62. NumMuxBoards property 12 17 Nyquist frequency 4 15 Nyquist theorem 1 34 O obj2mfile function 10 76 object constructor 3 4 onboard clock 1 22 one shot acquisition 5 29 online help 2 20 Oscilloscope displaying channels 9 4 exporting data 9 23 making measurements 9 17 opening 9 2 saving and loading the configuration 9 25 scaling channel data 9 11 triggering 9 14 OutOfDataMode property 12 18 output range 6 34 OutputRange property 11 56 outputting data 3 22 continuous 6 21 holding the last value 12 18 single point 10 84 overloaded functions 10 2 overrange condition 1 21 P parallel port adaptor 7 3 device specific properties 12 6 Parent property 11 58 PC clock 1 22 peekdata function 10 78 polarity 1 21 engineering units AI 5 55 polling the data block 5 10 port characteristics 7 5 Port property 11 59 PortAddress property 12 19 port configurable device 7 5 postriggers 5 27 precision 1 30 pretriggers 5 26 previewing data 5 8 properties BiDirectionalBit 12 8 BitsPerSample 12 9 BufferingConfig 11 15 BufferingMode 11 17 Channel 11 18 ChannelName 11 20 ChannelSkew 11 21 ChannelSkewMode 11 22 ClockSource 11 24 COLA 12 10 Coupling 12 11 DataMissedFcn 11 26 DefaultChannelValue 11 27 Index Direction 11 28 DriveAISenseToGround 12 12 EventLog 11 29 GroundingMode 12 13 HwChannel 11 31 HwLine 11 33 Index 11 34 InitialTriggerTime 11 36 InputMode 12 14 InputOverRangeFcn 11 38 InputRange 11 39 InputSource 12 16
63. Off Generating Timer Events Example Generating Timer Events This example illustrates how to generate timer events for a DIO object The callback function daqcallback displays the event type and device object name Note that you must issue a stop command to stop the execution of the object You can run this example by typing daqdoc7_2 at the MATLAB command line 1 Create a device object Create the digital I O object dio for a National Instruments board The installed adaptors and hardware IDs are found with daqhwinfo dio digitalio nidaq 1 2 Add lines Add eight input lines from port 0 line configurable addline dio 0 7 in 3 Configure property values Configure the timer event to call daqcallback every five seconds set dio TimerFcn daqcallback set dio TimerPeriod 5 0 Start the digital I O object You must issue a stop command when you no longer want to generate timer events start dio The pause command ensures that two timer events are generated when you run daqdoc7_2 from the command line pause 11 4 Clean up When you no longer need dio you should remove it from memory and from the MATLAB workspace delete dio clear dio 7 19 7 Digital Input Output Evaluating the Digital 1 O Object Status You can evaluate the status of a digital I O DIO object by e Returning the value of the Running property this is useful only if timer events are generated e Invoking the display
64. PE True Expression peak2peak HorizontalAlignment left Label SelectedColor iz VerticalAlignment top OK cancel Help 9 22 Exporting Data Exporting Data You can export this information to the MATLAB workspace a figure or a MAT file e Channel data Data associated with a hardware channel a math channel or a reference channel e Measurements Data associated with a defined measurement Note that some measurements such as the horizontal and the vertical cursor have no data to save Channels You export channel data with the Channel Exporter GUI which you open by selecting the File gt Export gt Channels menu item The GUI shown below is configured to export 1000 samples for both hardware channels to the workspace as a structure which contains horizontal and vertical scaling information The variable name for the CHO data is c0 and the variable name for the CH1 data is c1 xi Save the channel data and scaling Data destination workspace scaling structure x T information as a structure Samples to export Number in display Count fiooo Save the most recent 1000 samples Select the channels to export z Type Name Data Source Variable Name lHaraware CHO Hardware ch od Save the data for both channels to Hardware CH1 Hardware ch c1 the variable names cO and c1 Export Close Help 9 23 9 softscope The Data Acquisition Oscilloscope
65. Properties TriggerCondition TriggerType TriggerDelay Purpose Description Characteristics Values Example See Also Specify the delay value for data logging You can define both pretriggers and postriggers Pretriggers are specified with a negative TriggerDelay value while postriggers are specified with a positive TriggerDelay value You can delay a trigger in units of time or samples with the TriggerDelayUnits property Pretriggers are not defined for hardware triggers or when TriggerType is Immediate Pretrigger samples are included as part of the total samples acquired per trigger as specified by the SamplesPerTrigger property If sample time pairs are returned to the workspace with the getdata function then the pretrigger samples are identified with negative time values Usage AI Common Access Read write Data type Double Read only Yes when running The default value is zero Create the analog input object ai and add one channel to it ai analoginput winsound ch addchannel ai 1 Configure ai to acquire 44 100 samples per trigger with 11 025 samples 0 25 seconds acquired as pretrigger data set ai SampleRate 44100 set ai TriggerType Manual set ai SamplesPerTrigger 44100 set ai TriggerDelay 0 25 Properties SamplesPerTrigger TriggerDelayUnits 11 91 TriggerDelayUnits Purpose Description Characteristics Values See Also 11 92 Specify th
66. Size Bytes Class dio 1x1 1308 digitalio object Grand total is 40 elements using 1308 bytes Once the object is created the properties listed below are automatically assigned values These general purpose properties provide descriptive information about the object based on its class type and adaptor Table 7 1 Descriptive Digital 1 O Properties Property Name Description Name Specify a descriptive name for the device object Type Indicate the device object type You can display the values of these properties for dio with the get function get dio Name Type ans nidaq1 DIO Digital I0 Creating a Digital I O Object The Parallel Port The PC supports up to three parallel ports that are assigned the labels LPT1 LPT2 and LPTS3 You can use any of these standard ports as long as they use the usual base addresses which are in hex 378 278 and 3BC respectively The port labels and addresses are typically configured through the PC s BIOS Additional ports or standard ports not assigned the usual base addresses are not accessible by the toolbox Most PCs that support MATLAB will include a single parallel port with label LPT1 and base address 378 To create a DIO object for this port parport digitalio parallel LPT1 Note The parallel port is not locked by MATLAB Therefore other applications or other instances of MATLAB can access the same parallel port which can result in a conflict
67. The trigger occurs as long as the analog signal is more than the specified value GateBelow The trigger occurs as long as the analog signal is less than the specified value GateInWindow The trigger occurs as long as the analog signal is within the specified range of values GateOutWindow The trigger occurs as long as the analog signal is outside the specified range of values Hardware Digital Triggering If TriggerType is HwDigital the trigger is given by a digital TTL signal For example to trigger your acquisition when the positive edge of a digital signal is detected ai analoginput mcc 1 addchannel ai 0 7 set ai TriggerType HwDigital set ai TriggerCondition TrigPosEdge Configuring Analog Input Triggers The diagram below illustrates how you connect a digital trigger signal to a PCI DAS1602 16 board A D External Trigger corresponds to pin 45 TTL signal A D External Trigger PCI DAS1602 16 board Hardware Analog Triggering If TriggerType is HwAnalog the trigger is given by an analog signal For example to trigger your acquisition when the trigger signal is between 4 volts and 4 volts ai analoginput mcc 1 addchannel ai 0 7 set ai TriggerType HwAnalog set ai TriggerCondition GateInWindow set ai TriggerConditionValue 4 0 4 0 The diagram below illustrates how you connect a
68. This Guide xiv Expected Background To use the Data Acquisition Toolbox you should have some familiarity with e The basic features of MATLAB e The capabilities of your hardware device e The basic concepts associated with acquiring live measured data If You Are a New User For a brief review of basic data acquisition concepts you should start with Chapter 1 Introduction to Data Acquisition Otherwise start with Chapter 2 Getting Started with the Data Acquisition Toolbox which provides simple examples that illustrate how to input and output data Then read the appropriate chapter based on the hardware subsystem you are using For example if you are acquiring data with an analog input subsystem you should read Chapter 4 Getting Started with Analog Input After you have successfully transferred data between your hardware device and MATLAB you should read the appropriate reference material as needed If you want detailed information about a specific function refer to Chapter 10 Function Reference If you want detailed information about a specific property refer to Chapter 11 Base Property Reference or Chapter 12 Device Specific Property Reference If You Are an Experienced User Start with the Data Acquisition Toolbox Release Notes for a description of new and modified toolbox features You should then read the appropriate reference material as needed If you want detailed information a
69. Usage AI Common Access Read write Data type String Read only No when running Values The default value is an empty string See Also Properties EventLog SamplesAcquiredFcnCount TimerFen 11 67 SamplesAcquiredFcnCount Purpose Description Characteristics Values See Also 11 68 Specify the number of samples to acquire for each channel group member before a samples acquired event is generated A samples acquired event is generated immediately after the number of samples specified by SamplesAcquiredFcnCount is acquired for each channel group member This event executes the callback function specified by the SamplesAcquiredFcn property Usage AI Common Access Read write Data type Double Read only Yes when running The default value is 1024 Properties SamplesAcquiredFcn SamplesAvailable Purpose Description Characteristics Values See Also Indicate the number of samples available per channel in the engine For analog input AI objects SamplesAvailable indicates the number of samples that can be extracted from the engine for each channel group member with the getdata function For analog output AO objects SamplesAvailable indicates the number of samples that have been queued with the putdata function and can be sent output to each channel group member After data has been extracted AI or output AO the SamplesAvailable value is reduced by the appropriate number of samples For AI
70. You cannot capture pretrigger data for immediate triggers or device specific hardware triggers Note Pretrigger data has negative relative time values associated with it This is because time 0 corresponds to the time the trigger event occurs and data logging is initiated Configuring Analog Input Triggers Capturing Posttrigger Data In some circumstances you might want to capture data after the trigger occurs Such data is called posttrigger data When capturing posttrigger data the SamplesPerTrigger property value and the number of posttrigger samples are equal Capturing posttrigger data is illustrated below Posttrigger samples Trigger occurs I Data stored in engine SamplesPerTrigger You can capture posttrigger data using any supported trigger type Example Voice Activation and Pretriggers This example modifies daqdoc5 3 such that 500 pretrigger samples are acquired You can run this example by typing daqdoc5_4 at the MATLAB command line 1 Create a device object Create the analog input object AlVoice for a sound card The installed adaptors and hardware IDs are found with daqhwinfo AIVoice analoginput winsound AIVoice analoginput nidaq 1 AIVoice analoginput mcc 1 J 2 Add channels Add one hardware channel to AIVoice chan addchannel AIVoice 1 chan addchannel AIVoice 0 For NI and MCC 5 27 5 Doing More with Analog Input 5 2
71. added to the device object Usage AI AO Common Channel DIO Common Line Access Read only Data type String Read only N A when running Device Objects For device objects Type has these possible values Analog Input The device object type is analog input Analog Output The device object type is analog output Digital IO The device object type is digital I O The value is automatically defined after the device object is created Channels and Lines For channels the only value of Type is Channel For lines the only value of Type is Line The value is automatically defined when channels or lines are added to the device object Units Purpose Description Characteristics Values See Also Specify the engineering units label Units is a string that specifies the engineering units label to associate with your data You should use Units in conjunction with the UnitsRange property Usage AI AO Channel Access Read write Data type String Read only No when running The default value is Volts Properties UnitsRange 11 99 UnitsRange Purpose Description Characteristics Values See Also 11 100 Specify the range of data as engineering units You use UnitsRange to scale your data to reflect particular engineering units For analog input objects the data is scaled while it is extracted from the engine with the getdata function according to the formula scaled value A D value uni
72. ai analoginput nidaq 1 chans addchannel ai 0 3 Acquire 1 second of data and display the logged event types start ai events ai EventLog events Type ans Start Trigger Stop To examine the data associated with the trigger event events 2 Data ans AbsTime 1999 2 12 14 54 52 5456 RelSample 0 Channel Trigger 1 Functions showdaqevents HwChannel Purpose Description Characteristics Values Example Specify the hardware channel ID All channels contained by a device object have a hardware channel ID and an associated MATLAB index The channel ID is given by HwChannel and the MATLAB index is given by the Index property The HwChannel value is defined when hardware channels are added to a device object with the addchannel function The beginning channel ID value depends on the hardware device For National Instruments hardware channel IDs are zero based begin at zero For Agilent Technologies hardware and sound cards channel IDs are one based begin at one For scanning hardware the scan order follows the MATLAB index Therefore the hardware channel associated with index 1 is sampled first the hardware channel associated with index 2 is sampled second and so on To change the scan order you can assign the channel IDs to different indices using HwChannel Usage AI AO Channel Access Read write Data type Double Read only Yes when running Values are automatic
73. aini for a National Instruments board and add two channels to each device object aiwin analoginput winsound addchannel aiwin 1 2 aini analoginput nidaq 1 addchannel aini 0 1 daqmem See Also To display the total memory used by all existing device objects out daqmem out UsedDaq ans 69120 To configure the maximum memory used by aiwin to 640 KB daqmem aiwin 640000 To configure the maximum memory used by each device object with one call to daqmem daqmem aiwin aini 640000 480000 Properties Buf feringConfig MaxSamplesQueued 10 37 daqpropedit Purpose Syntax Arguments Description Remarks 10 38 Open the Data Acquisition Property Editor daqpropedit daqpropedit obj obj A device object daqpropedit opens the Data Acquisition Property Editor All existing device objects are displayed in the editor daqpropedit obj opens the editor for the specified device object obj The Data Acquisition Property Editor is a graphical user interface GUI that allows you to e List all existing device objects as well as the channels or lines they contain Configure property values e Display property characteristics e Display property help As shown below you can also invoke the property editor via the Workspace browser by right clicking a device object and selecting Explore gt Call Property Editor from the context menu inixi File Edit View Web
74. analoginput winsound addchannel ai 1 2 The commands shown below are some of the ways you can use get to return property values chan get ai Channel1 out get ai SampleRate TriggerDelayUnits out get ai get chan 1 Units get chan Index HdwChannel1 ChannelName Functions set setverify getdata Purpose Syntax Arguments Description Extract data time and event information from the data acquisition engine data getdata obj data getdata obj samples data getdata obj type data getdata obj samples type data time getdata data time abstime getdata data time abstime events getdata obj An analog input object samples The number of samples to extract If samples is not specified the number of samples extracted is given by the SamplesPerTrigger property type Specifies the format of the extracted data as double the default or as native data An m by n array where m is the number of samples extracted and n is the number of channels contained by obj time An m by 1 array of relative time values where m is the number of samples extracted Relative time is measured with respect to the first sample logged by the engine abstime The absolute time of the first trigger returned as a clock vector This value is identical to the value stored by the InitialTriggerTime property events A structure containing a list of events that o
75. analogoutput nidaq 1 2 Add channels Add one hardware channel to AO chan addchannel A0O 0 3 Configure property values Create the data to be queued freq 500 w 2 pi freq t linspace 0 2 20000 data 2 sin w t 6 35 6 Analog Output 6 36 Configure the sampling rate to 5 kHz configure the trigger to repeat two times and scale the data to cover the full output range of the D A converter Because the peak to peak amplitude of the queued data is 4 UnitsRange is set to 2 2 which scales the output data to 20 volts peak to peak set AO SampleRate 5000 set AO RepeatOutput 2 set chan UnitsRange 2 2 Queue the data with one call to putdata putdata A0O data Output data Start AO and wait until all the data is output start AO waittilstop A0 6 Clean up When you no longer need AO you should remove it from memory and from the MATLAB workspace delete A0 clear AO Starting Multiple Device Objects Starting Multiple Device Objects With the Data Acquisition Toolbox you can start multiple device objects You might find this feature useful when simultaneously using your hardware s analog output AO and analog input AI subsystems For example suppose you create the analog input object ai and the analog output object ao for a sound card and add one channel to each device object ai analoginput winsound addchannel ai 1 ao analogoutput wins
76. ans 8 1 Functions length 10 95 softscope Purpose Syntax Arguments Description Remarks 10 96 Open the data acquisition oscilloscope softscope softscope obj softscope fname si obj An analog input object fname si Name of the file containing Oscilloscope settings softscope opens the Hardware Configuration graphical user interface GUD which allows you to configure the hardware device to be used with the Oscilloscope The Oscilloscope opens when you press the OK button and at least one hardware channel is selected softscope obj opens the Oscilloscope configured to display the data acquired from the analog input object obj obj must contain at least one hardware channel softscope fname si opens the Oscilloscope using the settings saved in the softscope file specified by fname fname is generated from the Oscilloscope s File gt Save or File gt Save As menu item The Oscilloscope is a graphical user interface GUI that allows you to e Stream acquired data into a display e Scale displayed data and configure triggers and measurements e Configure analog input hardware settings e Export measurements and acquired data To support these tasks the Oscilloscope includes several helper GUIs which are described below softscope Hardware Configuration The Hardware Configuration GUI allows you to add channels from a particular hardware device to the Oscilloscope You can configure t
77. by muxboard For each mux board muxidx can range from 0 31 for differential inputs and 0 63 for single ended inputs muxboard and muxidx are vectors of equal length scanidx muxchanidx obj absmuxidx returns the scanning index number of the multiplexed channel specified by absmuxidx absmuxidx is the absolute index of the channel independent of the mux board For single ended inputs the first mux board has absolute index values that range between 0 and 63 the second mux board has absolute index values that range between 64 and 127 the third mux board has absolute index values that range between 128 and 191 the fourth mux board has absolute index values that range between 192 and 255 For example the absolute index value of the second single ended channel on the fourth mux board muxboard is 4 and muxidx is 1 is 193 scanidx identifies the column number of the data returned by getdata and peekdata Refer to the AMUX 64T User Manual for more information about adding mux channels based on hardware channel IDs and the number of mux boards used muxchanidx Example Create the analog input object ai for a National Instruments board that is connected to four AMUX 64T multiplexers and add 256 channels to ai using addmuxchannel ai analoginput nidaq 1 ai InputType SingleEnded ai NumMuxBoards 4 addmuxchannel ai The following two commands return a scanned index value of 14 scanidx muxchanidx ai 4 1 scani
78. ch addchannel ai 1 2 set ai TriggerRepeat 2 Start ai and display the trigger event information with showdaqevents start ai showdaqevents ai 2 4 2 Trigger 1 17 07 06 O0 Channel N A 3 Trigger 2 17 07 07 8000 Channel N A 4 Trigger 3 17 07 08 16000 Channel N A See Also Functions daqread getdata Properties EventLog 10 93 size Purpose Syntax Arguments Description 10 94 Return the size of a device object channel group or line group d size obj m1 m2 m3 mn size obj m size obj dim d size obj Channel m1 m2 m3 mn size obj Channel m size obj Channel dim d size obj Line m1 m2 m3 mn size obj Line m size obj Line dim obj A device object or array of device objects dim The dimension obj Channel The channels contained by obj obj Line The lines contained by obj d A two element row vector containing the number of rows and columns in obj m1 m2 m3 mn Each dimension of obj is captured in a separate variable m The length of the dimension specified by dim d size obj returns the two element row vector d m n containing the number of rows and columns in obj m1 m2 m3 mn size obj returns the length of the first n dimensions of obj to separate output variables For example m n size obj returns the number of rows to m and the number of columns to n m size obj dim returns the length of the dimension
79. channel 0 Display only the first CH1 Hardware channel 1 p two channels CH2 Hardware channel 2 CH3 Hardware channel 3 CH4 Hardware channel 4 i CH5 Hardware channel 5 NE a CHE Hardware channel 6 CH Hardware channel 7 OOOO ORs Click the OK button to open the Oscilloscope You can also open the Hardware Configuration GUI by selecting the Edit gt Hardware menu item You might want to do this to reconfigure an existing hardware device or to select a new hardware device Additionally you can change the sampling rate of the added channels with the New Sample Rate GUI which is shown below You open this GUI by selecting the Edit gt Sample Rate menu item New Sample Rate x Enter the new sample rate 5000 OK Cancel 9 3 9 softscope The Data Acquisition Oscilloscope Displaying Channels Click the Trigger button to begin streaming data into the display The data from each channel defines a unique trace line To quickly scale the data right click the display and select Autoscale from the menu Oscilloscope me O x File Edit Help Triggers Acquire Continuous x Samples to acquire Fill the display C Count foo Channel Scaling Horizontal ffset Scale CH1 C f Vertical A Type independent 2 CH1 hannel CHO f offset Scale ndition Rising z X 633 80ms Y
80. class type and ID Table 4 2 Descriptive Analog Input Channel Properties Property Name Description HwChannel Specify the hardware channel ID Index Indicate the MATLAB index of a hardware channel Parent Indicate the parent device object of a channel Type Indicate a channel You can display the values of these properties for chans with the get function get chans HwChannel Index Parent Type ans 0 1 1x1 analoginput Channel 1 2 1x1 analoginput Channel If you are using scanning hardware then the MATLAB indices define the scan order index 1 is sampled first index 2 is sampled second and so on Note The number of channels you can add to a device object depends on the specific board you are using Some boards support adding channels in any order and adding the same channel multiple times while other boards do not Additionally each channel might have its own input range which is verified with each acquired sample The collection of channels you add to a device object is sometimes referred to as a channel gain list or a channel gain queue For scanning hardware these channels define the scan order Adding Channels to an Analog Input Object Referencing Individual Hardware Channels As described in the preceding section you can access channels with the Channel property or with a channel object To reference individual channels you must specify either MATLAB indices or descrip
81. clock and is generally limited to sampling rates below 500 Hz The computer clock is referred to as the software clock in this guide External Clock An external clock is often used when the sampling rate is low and not constant For example an external clock source is often used in automotive applications where samples are acquired as a function of crank angle The Analog Input Subsystem Channel Configuration You can configure input channels in one of these two ways e Differential e Single ended Your choice of input channel configuration might depend on whether the input signal is floating or grounded A floating signal uses an isolated ground reference and is not connected to the building ground As a result the input signal and hardware device are not connected to a common reference which can cause the input signal to exceed the valid range of the hardware device To circumvent this problem you must connect the signal to the onboard ground of the device Examples of floating signal sources include ungrounded thermocouples and battery devices A grounded signal is connected to the building ground As a result the input signal and hardware device are connected to a common reference Examples of grounded signal sources include nonisolated instrument outputs and devices that are connected to the building power system Note For more information about channel configuration refer to your hardware documentation Differe
82. currently used by ai while the MaxBytes field tells you the maximum memory that ai can use to store acquired data Note that the value returned for MaxBytes depends on the total available computer memory and might be different for your platform You can verify the UsedBytes value with the formula given in the previous section However you must first find the size in bytes of each sample using the daqhwinfo function hwinfo daqhwinfo ai hwinfo NativeDataType ans int16 The value of the NativeDataType field tells you that each sample requires two bytes Therefore the initial allocated memory is 122 880 bytes However if you want to keep all the acquired data in memory then 176 400 bytes are required Example Managing Memory Resources The Data Acquisition Toolbox will accommodate this memory requirement by dynamically increasing the number of data blocks after you start ai start ai After all the data is acquired you can examine the final number of data blocks used by ai ai BufferingConfig ans 1024 44 The final total memory used is daqmem ai ans UsedBytes 180224 MaxBytes 18011136 Note that this was more than enough memory to store all the acquired data B 5 B Managing Your Memory Resources B 6 Glossary C Glossary Accuracy Acquiring data Actuator Adaptor A D converter Analog input subsystem Analog output subsystem Bandwidth Base property Callback
83. data is repeated four times and two putdata calls are issued a total of 10 seconds of data is output duration 1 set AO SampleRate 8000 ActualRate get A0O SampleRate len ActualRate duration set AO RepeatOutput 4 data sin linspace 0 2 pi 500 1len putdata A0O data putdata A0 data Managing Output Data 4 Output data Start AO and wait for the device object to stop running start AO waittilstop A0 11 5 Clean up When you no longer need AO you should remove it from memory and from the MATLAB workspace delete AO clear AO 6 19 6 Analog Output Configuring Analog Output Triggers 6 20 An analog output trigger is defined as an event that initiates the output of data As shown in the figure below when a trigger occurs the Sending property is automatically set to On and queued data is output from the engine to the hardware subsystem Sending Off Sending On rma gt __ Time Queue data Trigger occurs Output data in engine to hardware Properties associated with analog output triggers are given below Table 6 7 Analog Output Trigger Properties Property Name Description InitialTriggerTime Indicate the absolute time of the first trigger TriggerFen Specify the M file callback function to execute when a trigger occurs TriggersExecuted Indicate the number of triggers that execute TriggerType Specify the type of trigger to execute Ex
84. documentation examples you can e Input single values using the getsample function or output single values using the putsample function e Configure the ClockSource property to Software The Quick Reference Guide The Quick Reference Guide provides a complete overview of the toolbox capabilities functions and properties You might find it useful to print this guide and keep it handy when using the toolbox You can access this guide through the Help browser Demos The toolbox includes a large collection of demos which are divided into two main groups command line tutorials and graphical applications You can access all demos through the Help browser s Demos pane Use the following command to open the Help browser to the toolbox demos demo toolbox Data Acquisition Note that the analog input and analog output command line tutorials require that you have a sound card installed The digital I O tutorials require that you have a supported National Instruments board with digital I O capabilities For your convenience the command line tutorials are collected together using a graphical user interface GUI To open this GUI directly from the command line type daqschool 2 13 2 Getting Started with the Data Acquisition Toolbox 2 14 The daqschool GUI is shown below Data Acquisition Toolbox Tutorials p x Analog Input Analog Output Digital YO Common The buttons in this window will launch the Data A
85. e You are using a hardware driver that is incompatible with the toolbox e Your hardware is not functioning properly What Driver Are You Using The Data Acquisition Toolbox is compatible only with specific versions of the HP E1432 driver and is not guaranteed to work with any other versions You can find out which driver version you are using with the Soft Front Panel which is described in the next section If you think your driver is incompatible with the Data Acquisition Toolbox then you should verify that your hardware is functioning properly before updating drivers If your hardware is functioning properly then you are probably using unsupported drivers Visit the Agilent Web site at http agilent com for the latest drivers For a list of the HP E1432 driver versions that are compatible with the Data Acquisition Toolbox refer to the product page on the MathWorks Web site at http www mathworks com products daq Agilent Technologies Hardware Is Your Hardware Functioning Properly To troubleshoot your Agilent hardware you should use the HP E1432 Soft Front Panel The Soft Front Panel allows you to test each module supported by the HP E1432 driver software and is installed as part of this software You can access the Soft Front Panel through the Windows Start button Start gt Programs gt hpe1432 gt HP E1432 Soft Front Panel For example suppose you want to verify that the HP E1432 module is operating correctly To
86. events that occurred up to the getdata call The possible events that can be returned are identical to those stored by the EventLog property More About getdata e In most circumstances getdata returns all requested data and does not miss any samples In the unlikely event that the engine cannot keep pace with the hardware device it is possible that data is missed If data is missed the DataMissedFcn property is called and the device object is stopped e getdata is a blocking function because it returns execution control to the MATLAB workspace only when the requested number of samples are extracted from the engine for each channel group member e You can issue C Control C while getdata is blocking This will not stop the acquisition but will return control to MATLAB e The amount of data that you can extract from the engine is given by the SamplesAvailable property getdata Example More About Extracting Data From the Engine Once the requested data is extracted from the engine the SamplesAvailable property value is automatically reduced by the number of samples returned e If the requested number of samples is greater than the samples to be acquired then an error is returned e Ifthe requested data is not returned in the expected amount of time an error is returned The expected time to return data is given by the time it takes the engine to fill one data block plus the time specified by the Timeout property e If
87. for more information about channel configuration e Use signal wires that are twisted together rather than separate Keep the signal wires as short as possible Keep the signal wires as far away as possible from environmental electrical activity Filtering Filtering also reduces signal noise For many data acquisition applications a low pass filter is beneficial As the name suggests a low pass filter passes the lower frequency components but attenuates the higher frequency components The cut off frequency of the filter must be compatible with the frequencies present in the signal of interest and the sampling rate used for the A D conversion A low pass filter that s used to prevent higher frequencies from introducing distortion into the digitized signal is known as an antialiasing filter if the cut off occurs at the Nyquist frequency That is the filter removes frequencies greater than one half the sampling frequency These filters generally have a sharper cut off than the normal low pass filter used to condition a signal Antialiasing filters are specified according to the sampling rate of the system and there must be one filter per input signal Matching the Sensor Range and A D Converter Range When sensor data is digitized by an A D converter you must be aware of these two issues e The expected range of the data produced by your sensor This range depends on the physical phenomena you are measuring and the output range
88. frequency and period measurement and pulse train generation This subsystem is not supported by the Data Acquisition Toolbox A digital to analog subsystem A process that encompasses all the steps you must take to acquire data using an analog input object output data using an analog output object or read values from or write values to digital I O lines These steps are broken down into initialization configuration execution and termination The smallest slice of memory that the data acquisition engine can usefully manipulate A MATLAB object that allows you to access a hardware device A property that applies only for specific hardware devices For example the BitsPerSample property is supported only for sound cards Input channel configuration where there are two signal wires associated with each input signal one for the input signal and one for the reference return signal The measurement is the difference in voltage between the two wires which helps reduce noise and any voltage common to both wires Hardware that sends or receives digital values logic levels This is also referred to as a DIO subsystem Direct memory access DMA is a system of transferring data whereby samples are automatically stored in system memory while the processor does something else C 3 C Glossary C 4 Engine Engineering units properties Event Execution FIFO buffer Full duplex Input range Interrupts
89. in the specified target Logging Off Logging On ot gt Time Trigger occurs Log data to engine and disk file When defining a trigger you must specify the trigger type Additionally you might need to specify one or more of these parameters e A trigger condition and trigger condition value e The number of times to repeat the trigger e A trigger delay e A callback function to execute when the trigger event occurs Properties associated with analog input triggers are given below Table 5 6 Analog Input Trigger Properties Property Name Description InitialTriggerTime Indicate the absolute time of the first trigger ManualTriggerHwOn Specify that the hardware device starts when a manual trigger is issued TriggerFen Specify the M file callback function to execute when a trigger occurs 5 19 5 Doing More with Analog Input 5 20 Table 5 6 Analog Input Trigger Properties Continued Property Name Description TriggerChannel TriggerCondition TriggerCondition Value TriggerDelay TriggerDelayUnits TriggerRepeat TriggersExecuted TriggerType Specify the channel serving as the trigger source Specify the condition that must be satisfied before a trigger executes Specify one or more voltage values that must be satisfied before a trigger executes Specify the delay value for data logging Specify the units in which trigger delay data is measured Specify t
90. input object ai add two channels and define the trigger source as channel 2 ai analoginput winsound ch addchannel ai 1 2 set ai TriggerChannel ch 2 t ai TriggerType Software Properties TriggerCondition TriggerConditionValue TriggerType TriggerCondition Purpose Description Characteristics Values Specify the condition that must be satisfied before a trigger executes The available trigger conditions depend on the value of TriggerType If TriggerType is Immediate or Manual the only available TriggerCondition is None If TriggerType is Software then TriggerCondition can be Rising Falling Leaving or Entering These trigger conditions require one or more voltage values to be specified for the TriggerConditionValue property Based on the hardware you are using additional trigger conditions might be available Usage AI Common Access Read write Data type String Read only Yes when running All Supported Hardware The following trigger condition is used when TriggerType is Immediate or Manual None No trigger condition is required The following trigger conditions are available when TriggerType is Software Rising The trigger occurs when the signal has a positive slope when passing through the specified value Falling The trigger occurs when the signal has a negative slope when passing through the specified value Leaving The trigger occurs when the signal leaves the spe
91. many of the properties at any time while the device object exists However some properties are not configurable while the object is running Use the propinfo function or refer to Chapter 11 Base Property Reference for information about when a property is configurable The syntax used to configure common and channel line properties is described below The examples are based on the analog input object ai created in Returning Property Names and Property Values on page 3 14 Common Properties You can configure a single property value using the set function set ai TriggerType Manual or the dot notation ai TriggerType Manual To configure values for multiple properties you can supply multiple property name property value pairs to set set ai SampleRate 44100 Name Test1 winsound Note that you can configure only one property value at a time using the dot notation Channel and Line Properties To configure channel line properties for one or more channels lines contained by a device object you must use the Channel Line property For example to configure the SensorRange property for the first channel contained by ai you can use the set function set ai Channel 1 SensorRange 2 2 or the dot notation ai Channel 1 SensorRange 2 2 Configuring and Returning Properties To configure values for multiple channel or line properties you supply multiple property name property value
92. maxindex 441 The answer is 441 Hz Note The fundamental frequency is not always the frequency component with the largest amplitude A more sophisticated approach involves fitting the observed frequencies to a harmonic series to find the fundamental frequency 4 Getting Started with Analog Input 4 18 Acquiring Data with a National Instruments Board Suppose you must verify that the nominal frequency of a sine wave generated by a function generator is 1 00 kHz To perform this task you will input the function generator signal into a National Instruments board You will then perform a fast Fourier transform FFT on the acquired data to find the nominal frequency of the generated sine wave The setup for this task is shown below Data Source National Instruments Board Data Sink 01 00 000001 Piute oe NVA MATLAB workspace A D gt Configuring the Data Acquisition Session For this example you will acquire 1 second of data on one input channel The board is set to a sampling rate of 10 kHz which is well above the frequency of interest After you connect the input signal to the board you will trigger the acquisition one time using a manual trigger You can run this example by typing daqdoc4_2 at the MATLAB command line 1 Create a device object Create the analog i
93. need to condition an input signal by amplifying it or by removing unwanted frequency components Output signals might need conditioning as well However only input signal conditioning is discussed in this chapter The computer The computer provides a processor a system clock a bus to transfer data and memory and disk space to store data Software Data acquisition software allows you to exchange information between the computer and the hardware For example typical software allows you to configure the sampling rate of your board and acquire a predefined amount of data 1 3 T introduction to Data Acquisition 1 4 The data acquisition components and their relationship to each other are shown below Physical phenomena Data Acquisition System ae a E ae ee ee ee I Sensor y Signal conditioning Ls Acquisition y hardware Computer Software Actuator kK E ob ee en Data EE analysis ysica phenomena The figure depicts the two important features of a data acquisition system e Signals are input to a sensor conditioned converted into bits that a computer can read and analyzed to extract meaningful information For example sound level data is acquired from a microphone amplified digitized by a sound card and stored in MATLAB for subsequent analysis of frequency content The Data Acquisition System e Data from a computer
94. number of bits used for the conversion Most modern converters use 12 or 16 bits Typically the converter selects the digital value that is closest to the actual sampled value The figure below shows a 1 Hz sine wave quantized by a 3 bit A D converter LAN A 1 Amplitude wo T 0 f f n f fi 0 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 1 Time sec T introduction to Data Acquisition The number of quantized values is given by 2 8 the largest representable value is given by 111 27 2 2 7 0 and the smallest representable value is given by 000 0 0 Quantization Error There is always some error associated with the quantization of a continuous signal Ideally the maximum quantization error is 0 5 least significant bits LSBs and over the full input range the average quantization error is zero As shown below the quantization error for the previous sine wave is calculated by subtracting the actual signal from the quantized signal 1 20 PANNA NA LVN AN L 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 Time sec The Analog Input Subsystem Input Range and Polarity The input range of the analog input subsystem is the span of input values for which a conversion is valid You can change the input range by selecting a different gain value For example National Instruments AT MIO 16E 1 board has eight gai
95. number of samples to acquire for each analog input channel group member for each trigger that occurs If SamplesPerTrigger is set to Inf then the analog input object continually acquires data until a stop function is issued or an error occurs The default value of SamplesPerTrigger is calculated by the data acquisition engine such that one second of data is acquired This calculation is based on the value of SampleRate Usage AI Common Access Read write Data type Double Read only Yes when running The default value is set by the engine such that one second of data is acquired Create the analog input object ai for a sound card and add two channels to it ai analoginput winsound addchannel ai 1 2 By default a one second acquisition in which 8000 samples are acquired for each channel is defined To define a two second acquisition at the same sampling rate set ai SamplesPerTrigger 16000 Functions stop Properties SampleRate 11 73 Sending Purpose Indicate whether data is being sent to the hardware device Description Along with the Running property Sending reflects the state of an analog output object Sending can be On or Off Sending is automatically set to On when a trigger occurs When Sending is On queued data is being output to the analog output subsystem Sending is automatically set to Off when the queued data has been output an error occurs or a stop function is issued When Sending
96. object obj and any channels or lines contained by obj Typing obj at the command line produces the same summary information disp obj Channel index displays summary information for the specified channels contained by obj Typing obj Channel index at the command line produces the same summary information disp obj Line index displays summary information for the specified lines contained by obj Typing obj Line index at the command line produces the same summary information You can invoke disp by typing the device object at the MATLAB command line or by excluding the semicolon when e Creating a device object e Adding channel or lines e Configuring property values using the dot notation 10 53 disp As shown below you can also display summary information via the Workspace browser by right clicking a device object a channel object or a line object and selecting Explore gt Display Summary from the context menu lox File Edit View Web Window Help o gt a A sxf z e ai spa 1332 analoginput object 24 do Open Select All Access context pop up menus Ready by right clicking a device object Display Hardware Info Show DAQ Events Import Data Save Selection As Save Workspace As DAQ Help Copy Delete Clear Workspace Rename Example All the commands shown below produce summary information for the device object AI or the channels contained by AI AI
97. objects SamplesAvailable is reset to zero after a start function is issued For AI objects use the SamplesAcquired property to find out how many samples have been acquired since the start function was issued For AO objects use the SamplesOutput property to find out how many samples have been output since the start function was issued Usage AI AO Common Access Read only Data type Double Read only N A when running The value is automatically updated based on the number of samples acquired analog input or sent analog output The default value is zero Functions start Properties SamplesAcquired SamplesOutput 11 69 SamplesOutput Purpose Description Characteristics Values See Also 11 70 Indicate the number of samples output per channel from the engine SamplesOutput is continuously updated to reflect the current number of samples output by an analog output object It is reset to zero after the device objects stops and data has been queued with the putdata function Use the SamplesAvailable property to find out how many samples are available to be output from the engine Usage AO Common Access Read only Data type Double Read only N A when running The value is continuously updated to reflect the current number of samples output The default value is zero Functions putdata Properties SamplesAvailable SamplesOutputFcn Purpose Description Characteristics Values See
98. of the sensor e The range of your A D converter For many devices the hardware range is specified by the gain and polarity You should select the sensor and hardware ranges such that the maximum precision is obtained and the full dynamic range of the input signal is covered 1 33 T introduction to Data Acquisition 1 34 For example suppose you are using a microphone with a dynamic range of 20 dB to 140 dB and an output sensitivity of 50 mV Pa If you are measuring street noise in your application then you might expect that the sound level never exceeds 80 dB which corresponds to a sound pressure magnitude of 200 mPa and a voltage output from the microphone of 10 mV Under these conditions you should set the input range of your data acquisition card for a maximum signal amplitude of 10 mV or a little more How Fast Should a Signal Be Sampled Whenever a continuous signal is sampled some information is lost The key objective is to sample at a rate such that the signal of interest is well characterized and the amount of information lost is minimized If you sample at a rate that is too slow then the signal is undersampled and aliasing can occur Aliasing can occur for both rapidly varying signals and slowly varying signals For example suppose you are measuring temperature once a minute If your acquisition system is picking up a 60 Hz hum from an a c power supply then that hum will appear as constant noise level if you a
99. one channel to it ao is configured to output 8 000 samples using the default sampling rate of 8000 Hz ao analogoutput winsound addchannel ao 1 data sin linspace 0 1 8000 putdata ao data start ao Configuring Analog Output Triggers TriggersExecuted returns the number of triggers executed ao TriggersExecuted ans 1 You can use showdaqevents to return information for all events that occurred while ao was executing showdaqevents ao 1 Start 10 43 25 0 2 Trigger 10 43 25 O 3 Stop 10 43 26 8000 For more information about recording and retrieving event information refer to Recording and Retrieving Event Information on page 6 28 When Did the Trigger Occur You can return the absolute time of the trigger with the InitialTriggerTime property Absolute time is returned as a clock vector in the form year month day hour minute seconds For example the absolute time of the trigger event for the preceding example is abstime ao InitialTriggerTime abstime 1 0e 003 1 9990 0 0040 0 0170 0 0100 0 0430 0 0252 To convert the clock vector to a more convenient form you can use the sprintf function t fix abstime sprintf d d d t 4 t 5 t 6 ans 10 43 25 As shown in the preceding section you can also evaluate the absolute time of the trigger event with the showdagevents function 6 23 6 Analog Output 6 24 Device Specific Hardware Triggers
100. one time For prototype Option 1D4 sources one of the two must be enabled at all times By default the constant level output is enabled and the sum input is disabled Vendor Usage Access Data Type Read only when running Off On Agilent Technologies AO Channel Read write String No Disable the source sum input Enable the source sum input TransferMode Purpose Description Specify how data is transferred from the data acquisition device to system memory For National Instruments hardware TransferMode can be Interrupts or SingleDMA for both analog input and analog output subsystems If TransferMode is Interrupts then data is transferred from the hardware first in first out memory buffer FIFO to system memory using interrupts If TransferMode is SingleDMA then data is transferred from the hardware FIFO to system memory using a single direct memory access DMA channel Some boards also support a TransferMode of DualDMA for analog input subsystems For example the AT MIO 16E 1 board supports this transfer mode If TransferMode is DualDMA then data is transferred from the hardware FIFO to system memory using two DMA channels Depending on your system resources data transfer via interrupts can significantly degrade system performance For Measurement Computing hardware TransferMode can be Default InterruptPerPoint DMA or InterruptPerBlock If TransferMode is Default the transfer mode is automatica
101. page 4 16 calculates the FFT of data and requires the values of SampleRate and SamplesPerTrigger as well as data as inputs daqdocfft outputs the frequency and magnitude of data which you can then plot 4 19 4 Getting Started with Analog Input The results are given below plot f mag grid on ylabel Magnitude dB xlabel Frequency Hz title Frequency Output by Function Generator Frequency Output by Function Generator 80 T T T T T T 60 J7 40H 4 20 Magnitude dB i 1 1 1 fi li 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 Frequency Hz 60 l This plot shows the nominal frequency around 1000 Hz A simple way to find actual frequency is shown below ymax maxindex max mag maxindex maxindex 994 The answer is 994 Hz 4 20 Evaluating the Analog Input Object Status Evaluating the Analog Input Object Status You can evaluate the status of an analog input AI object by e Returning the values of certain properties e Invoking the display summary Status Properties The properties associated with the status of your AI object allow you to evaluate e If the device object is running e If data is being logged to the engine or to a disk file e How much data has been acquired e How much data is available to be extracted from the engine The analog input status properties are given below Table 4 5 Analog Input Status Properties
102. pairs to set set ai Channel 1 SensorRange 2 2 ChannelName Chan1 To configure multiple property values for multiple channels chs ai Channel 1 2 set chs SensorRange ChannelName 2 2 Chani 0 4 Chan2 Specifying Property Names Device object property names are presented in this guide using mixed case While this makes the names easier to read you can use any case you want when specifying property names Additionally you need use only enough letters to identify the property name uniquely so you can abbreviate most property names For example you can configure the SampleRate property any of these ways set ai SampleRate 44100 set ai samplerate 44100 set ai sampler 44100 However when you include property names in an M file you should use the full property name This practice can prevent problems with future releases of the Data Acquisition Toolbox if a shortened name is no longer unique because of the addition of new properties Default Property Values If you do not explicitly define a value for a property then the default value is used All configurable properties have default values However the default value for a given property might vary based on the hardware you are using Additionally some default values are calculated by the engine and depend on the values set for other properties If the hardware driver adaptor specifies a default value for a property then that
103. pane and select Measurements from the Select the scope components list box The Scope Properties pane is shown below Scope Editor x Scope Scope Properties Select the scope components display display2 Triggers Select Measurements Edit the selected scope components properties Name Measurements ShowName PE True OK Cancel Help Measurement Properties You can configure measurement properties with the Measurement Properties editor You can open this editor two ways e Right click menu Place the mouse cursor in the Measurements pane of interest right click and select Edit Properties from the menu e Measurement Editor GUI Select Measurement from the Edit menu and then choose the Measurement Properties pane For this example use the Measurement Editor GUI to change the number of measurements stored for CH1 to be identical to the number of samples acquired for each trigger The steps are 1 Select CHO Pk2Pk in the Select the measurements list box 2 Edit the BufferSize property to be 1000 9 21 9 sottscope The Data Acquisition Oscilloscope The Measurement Properties pane is shown below x Measurement Measurement Properties Measurement Type Select the measurements Select the CHO peak to peak afl measurement CHO Vert X Editthe selected measurements properties BufferSize 1000 Store 1000 measurements Color Om DrawValueAlways Pa True Enabled
104. poll the appropriate property value Usage AI AO Common Access Read write Data type Double Read only Yes when running The default value is one second Functions getdata putdata Properties RunTimeErrorFen TimerFcn Purpose Description Characteristics Values See Also Specify the M file callback function to execute whenever a predefined period of time passes A timer event is generated whenever the time specified by the TimerPeriod property passes This event executes the callback function specified for TimerFcn Time is measured relative to when the device object starts running Some timer events might not be processed if your system is significantly slowed or ifthe TimerPeriod value is too small For example a common application for timer events is to display data However because displaying data is a CPU intensive task some of these events can be dropped To guarantee that events are not dropped you might want to use the SamplesAcquiredFen property analog input or the SamplesOutputFcn property analog output For digital I O objects timer events are typically used to update and display the state of the device object Timer event information is not stored in the EventLog property Usage AI AO DIO Common Access Read write Data type String Read only No when running The default value is an empty string Properties EventLog SamplesAcquiredFcn SamplesOutputFcn TimerPeriod 11 81
105. properly What Driver Are You Using The Data Acquisition Toolbox is compatible only with specific versions of the NI DAQ driver and is not guaranteed to work with any other versions For a list of the NI DAQ driver versions that are compatible with the Data Acquisition Toolbox refer to the product page on the MathWorks Web site at http www mathworks com products daq If you think your driver is incompatible with the Data Acquisition Toolbox then you should verify that your hardware is functioning properly before updating drivers If your hardware is functioning properly then you are probably using unsupported drivers Visit the National Instruments Web site at http www natinst com for the latest NI DAQ drivers You can find out which version of NI DAQ you are using with National Instruments Measurement amp Automation Explorer You should be able to access this program through the Windows Desktop The driver version is available through the Help menu Help gt About Measurement amp Automation Explorer gt System Info gt Software National Instruments Hardware For example the version of NI DAQ used by a PCI 6024E board is shown below Exploring PCI 6024E Device 1 gal PCI 6024E Device 1 A Desktop My Computer Internet Explorer Network Neighborhood LAA Measurement amp Automation Data Neighborhood Devices and Interfaces The NI DAQ device number Ox4DEF8C
106. putdata function For example to queue one second of data for each channel contained by the analog output object ao ao analogoutput winsound addchannel ao 1 2 data sin linspace 0 2 pi 8000 putdata ao data data putdata is a blocking function and will not return execution control to MATLAB until the specified data is queued putdata is described in detail in Managing Output Data on page 6 16 and in Chapter 10 Function Reference Starting the Analog Output Object You start an analog output object with the start function For example to start the analog output object ao start ao After start is issued the Running property is automatically set to On and both the device object and hardware device execute according to the configured and default property values While the device object is running you can continue to queue data However running does not necessarily mean that data is being output from the engine to the analog output hardware For that to occur a trigger must execute When the trigger executes the Sending property is automatically set to On Analog output triggers are described on Defining a Trigger on page 6 7 and Configuring Analog Output Triggers on page 6 20 Getting Started with Analog Output Stopping the Analog Output Object An analog output object can stop under one of these conditions e You issue the stop function e The queued data is output e A run t
107. relative trigger times by searching for NaNs in the returned data You can find the index location of the NaN in d or t using the isnan function index find isnan d index 22051 With this information you can find the relative time for the second trigger t2time t index 1 t2time 0 5980 5 34 Configuring Analog Input Triggers How Many Triggers Occurred You can find out how many triggers occurred with the TriggersExecuted property value The trigger number for each trigger executed is also recorded by the EventLog property A convenient way to access event log information is with the showdagevents function For example suppose you create the analog input object ai for a sound card and add one channel to it ai is configured to acquire 40 000 samples with five triggers using the default sampling rate of 8000 Hz ai analoginput winsound ch addchannel ai 1 set ai TriggerRepeat 4 start ai TriggersExecuted returns the number of triggers executed ai TriggersExecuted ans 5 showdagevents returns information for all the events that occurred while ai was executing showdaqevents ai 1 Start 10 22 04 0 2 Trigger 1 10 22 04 0 Channel N A 3 Trigger 2 10 22 05 8000 Channel N A 4 Trigger 3 10 22 06 16000 Channel N A 5 Trigger 4 10 22 07 24000 Channel N A 6 Trigger 5 10 22 08 32000 Channel N A 7 Stop 10 22 09 40000 For more information about recordin
108. result should maximize the measurement resolution and minimize the chance of an overrange condition The actual input range is given by the formula Actual input range Input range Gain The relationship between gain actual input range and precision for a unipolar and bipolar signal having an input range of 10 V is shown below Table 1 2 Relationship Between Input Range Gain and Precision Input Range Gain Actual Input Range Precision 12 Bit A D 0 to 10 V 1 0 0 to 10 V 2 44 mV 2 0 0to5V 1 22 mV 5 0 0to2V 0 488 mV 10 0 Otol V 0 244 mV 5 to 5 V 0 5 10 to 10 V 4 88 mV 1 0 5 to 5 V 2 44 mV 2 0 2 5 to 2 5 V 1 22 mV 5 0 1 0 to 1 0 V 0 488 mV 10 0 0 5 to 0 5 V 0 244 mV 1 31 T introduction to Data Acquisition 1 32 As shown in the table the gain affects the precision of your measurement If you select a gain that decreases the actual input range then the precision increases Conversely if you select a gain that increases the actual input range then the precision decreases This is because the actual input range varies but the number of bits used by the A D converter remains fixed Note With the Data Acquisition Toolbox you do not have to specify the range and gain Instead you simply specify the actual input range desired Noise Noise is considered to be any measurement that is not part of the phenomena of interest Noise can be generated within the electrical components of the input amplifi
109. run time error or stop event occurs set AI TriggerRepeat 3 time AI SamplesPerTrig AI SampleRate AI TriggerRepeatt1 set AI TriggerFcn daqcallback set AI RuntimeErrorFcn daqcallback set AI StopFcn daqcallback 4 Acquire data Start AI and wait for it to stop running The waittilstop function blocks the MATLAB command line and waits for AI to stop running start AI waittilstop AI time 5 Clean up When you no longer need AI you should remove it from memory and from the MATLAB workspace delete AI clear AI Passing Additional Parameters to a Callback Function This example illustrates how additional arguments are passed to the callback function Timer events are generated every 0 5 second to display data using the local callback function daqdoc5 7plot not shown below You can run this example by typing daqdoc5_7 at the MATLAB command line 5 53 5 Doing More with Analog Input 5 54 1 Create a device object Create the analog input object AI for a sound card The installed adaptors and hardware IDs are found with daqhwinfo AI analoginput winsound AI analoginput nidaqg 1 AI analoginput mcc 1 X Add channels Add one hardware channel to AI chan addchannel AI 1 chan addchannel AI 0 For NI and MCC Configure property values Define a 10 second acquisition and execute the M file daqdoc5 _7plot every 0 5 seconds Note that
110. same time and holds the values until the A D converter digitizes all the signals For high end systems there can be a separate A D converter for each input channel For example suppose you need to simultaneously measure the acceleration of multiple accelerometers to determine the vibration of some device under test To do this you must use SS H hardware because it does not have a channel skew In general you might need to use SS H hardware if your sensor signal changes significantly in a time that is less than the channel skew or if you need to use a transfer function or perform a frequency domain correlation The sample period for a multichannel configuration using SS H hardware is shown below Note that there is no channel skew A Group Group Group scan 1 scan 2 scan n O O O O O O pe 0 co 0 o a o fe o S tS O O O O O O K Sample period 3 gt Time The Analog Input Subsystem Quantization As discussed in the previous section sampling takes a snapshot of the input signal at an instant of time When the snapshot is taken the sampled analog signal must be converted from a voltage value to a binary number that the computer can read The conversion from an infinitely precise amplitude to a binary number is called quantization During quantization the A D converter uses a finite number of evenly spaced values to represent the analog signal The number of different values is determined by the
111. settling time the gain and the channel skew Channel skew is discussed in the next section 5 5 5 Doing More with Analog Input 5 6 Note Whenever the SampleRate value is changed the BufferingConfig property value is recalculated by the engine if the BufferingMode property is set to Auto Because Buf feringConfig indicates the memory used by the engine you should monitor this property closely Channel Skew Many data acquisition devices have one A D converter that is multiplexed to all input channels If you sample multiple input channels from scanning hardware then each channel is sampled sequentially following this procedure 1 A single input channel is sampled 2 The analog signal is converted to a digital value 3 The process is repeated for every input channel being used Because these channels cannot be sampled simultaneously a time gap exists between consecutively sampled channels This time gap is called the channel skew The channel skew and the sample period are illustrated below A Group Group Group scan 1 scan 2 scan n O O O O O O 2 O 0 0 I o o E 5 2 o o k gt k Sample period Channel skew Time Configuring and Sampling Input Channels As shown in the preceding figure a scan occurs when all channels in a group are sampled once and the scan rate is defined as the rate at which every channel in the group is sampled The properties associated with c
112. specified by the scalar dim For example size obj 1 returns the number of rows d size obj Channel returns the two element row vector d m n containing the number of rows and columns in the channel group obj Channel size Example See Also m1 m2 m3 mn size obj Channel returns the length of the first n dimensions of the channel group obj Channel to separate output variables For example m n size obj Channel returns the number of rows to m and the number of columns to n m size obj Channel dim returns the length of the dimension specified by the scalar dim For example size obj Channe1 1 returns the number of rows d size obj Line returns the two element row vector d m n containing the number of rows and columns in the line group obj Line m1 m2 m3 mn size obj Line returns the length of the first n dimensions of the line group obj Line to separate output variables For example m n size obj Line returns the number of rows to m and the number of columns to n m size obj Line dim returns the length of the dimension specified by the scalar dim For example size obj Line 1 returns the number of rows Create the analog input object ai for a National Instruments board and add eight channels to it ai analoginput nidaq 1 ch addchannel ai 0 7 To find the size of the device object size ai ans 1 1 To find the size of the channel group size ch
113. stored in a disk file to the MATLAB workspace with the daqread function Usage AI Common Access Read write Data type String Read only Yes when running Disk Acquired data is logged to a disk file Memory Acquired data is logged to memory Disk amp Memory Acquired data is logged to a disk file and to memory Functions daqread getdata Properties LogFileName LogToDiskMode 11 47 LogToDiskMode Purpose Description Characteristics Values See Also 11 48 Specify whether data events and hardware information are saved to one disk file or to multiple disk files LogToDiskMode can be set to Overwrite or Index If LogToDiskMode is set to Overwrite then the log file is overwritten each time start is issued If LogToDiskMode is set to Index a different disk file is created each time start is issued and these rules are followed The first log filename is specified by the initial value of LogFileName e If the specified file already exists it is overwritten and no warning is issued LogFileName is automatically updated with a numeric identifier after each file is written For example if LogFileName is initially specified as data daq then data daq is the first filename data01 daq is the second filename and so on Separate analog input objects are logged to separate files You can return data stored in a disk file to the MATLAB workspace with the daqread function If an error occurs during data loggi
114. the fields shown below Field Name Description Type The property data type Possible values are any callback double and string Constraint The type of constraint on the property value Possible values are bounded callback enum and none ConstraintValue The property value constraint The constraint can be a range of valid values or a list of valid string values DefaultValue The property default value ReadOnly If the property is read only a 1 is returned Otherwise a 0 is returned ReadOnlyRunning Ifthe property is read only while the device object is running a 1 is returned Otherwise a 0 is returned DeviceSpecific If the property is device specific a 1 is returned If a 0 is returned the property is supported for all device objects of a given type propinfo Example See Also out propinfo obj PropertyName returns the structure out for the property specified by PropertyName If PropertyName is a cell array of strings a cell array of structures is returned for each property Create the analog input object ai for a sound card and configure it to operate in stereo mode ai analoginput winsound addchannel ai 1 2 To capture all property information for all common ai properties out propinfo ai To display the default value for the SampleRate property out SampleRate DefaultValue ans 8000 To display all the property information for the InputRange property propinfo ai Cha
115. the input range of the analog input subsystem to maximize resolution and minimize the chance of an overrange condition How Are Acquired Samples Clocked Samples are acquired from an analog input subsystem at a specific rate by a clock Like any timing system data acquisition clocks are characterized their resolution and accuracy Timing resolution is defined as the smallest time interval that you can accurately measure The timing accuracy is affected by clock jitter Jitter arises when a clock produces slightly different values for a given time interval For any data acquisition system there are typically three clock sources that you can use the onboard data acquisition clock the computer clock or an external clock The Data Acquisition Toolbox supports all of these clock sources depending on the requirements of your hardware The Onboard Clock The onboard clock is typically a timer chip on the hardware board that is programmed to generate a pulse stream at the desired rate The onboard clock generally has high accuracy and low jitter compared to the computer clock You should always use the onboard clock when the sampling rate is high and when you require a fixed time interval between samples The onboard clock is referred to as the internal clock in this guide The Computer Clock The computer PC clock is used for boards that do not possess an onboard clock The computer clock is less accurate and has more jitter than the onboard
116. the preceding commands write to all eight lines contained by dio an eight element binary vector is required If you do not specify the number of bits then the minimum number of bits needed to represent the decimal value is used Alternatively you can create the binary vector without using dec2binvec bvdata logical 1 110100 0 putvalue dio bvdata Rules for Writing Digital Values Writing values to digital I O lines follows these rules e If the DIO object contains lines from a port configurable device then the data acquisition engine writes to all lines associated with the port even if they are not contained by the device object e When writing decimal values If the value is too large to be represented by the lines contained by the device object then an error is returned You can write to a maximum of 32 lines To write to more than 32 lines you must use a binvec value e When writing binvec values You can write to any number of lines There must be an element in the binary vector for each line you write to e You can always read from a line configured for output Reading values is discussed in Reading Digital Values on page 7 14 e An error is returned if you write a negative value or if you write to a line configured for input 7 13 7 Digital Input Output Reading Digital Values You can read values from one or more lines with the getvalue function getvalue requires the DIO object as an i
117. the property names for obj or a cell array of possible values set obj displays all configurable properties for obj If a property has a finite list of possible string values then these values are also displayed props set obj returns all configurable properties to props props is a structure array with fields given by the property names and possible property values contained in cell arrays if the property does not have a finite set of possible values then the cell array is empty set obj PropertyName displays the valid values for the property specified by PropertyName PropertyName must have a finite set of possible values props set obj PropertyName returns the valid values for PropertyName to props props is a cell array of possible values or an empty cell array if the property does not have a finite set of possible values 10 87 set Remarks Example 10 88 set obj PropertyName PropertyValue sets multiple property values with a single statement Note that you can use structures property name property value string pairs and property name property value cell array pairs in the same call to set set obj PN PV sets the properties specified in the cell array of strings PN to the corresponding values in the cell array PV PN must be a vector PV can be m by n where m is equal to the specified number of device objects channels or lines and n is equal to the length of PN set obj S where S is a
118. the requested data is returned To guarantee that acquired data contains no gaps is must be logged to memory or to a disk file Data stored in memory is extracted with the getdata function while data stored to disk is returned with the dagread function The destination for logged data is controlled with the LoggingMode property Usage AI Common Access Read only Data type String Read only N A when running Off Data is not logged to memory or a disk file On Data is logged to memory or a disk file Functions daqread getdata peekdata stop Properties LoggingMode Running LoggingMode Purpose Description Characteristics Values See Also Specify the destination for acquired data LoggingMode can be set to Disk Memory or Disk amp Memory If LoggingMode is set to Disk then acquired data as well as device object and hardware information is streamed to a disk file If LoggingMode is set to Memory then acquired data is stored in the data acquisition engine If LoggingMode is set to Disk amp Memory then acquired data is stored in the data acquisition engine and is streamed to a disk file When logging to the engine you must extract the data with the getdata function If the data is not extracted it might be overwritten When logging to disk you can specify the log filename with the LogFileName property and you can control the number of log files created with the LogToDiskMode property You can return data
119. time between timer events A timer event is generated whenever the time specified by TimerPeriod passes This event executes the callback function specified for TimerFcn Time is measured relative to when the device object starts running Running is On Starting a DIO object is discussed in the next section 7 Digital Input Output 7 18 Some timer events might not be processed if your system is significantly slowed or if the TimerPeriod value is too small For example a common application for timer events is to display data However because displaying data can be a CPU intensive task some of these events might be dropped For digital I O objects timer events are typically used to display the state of the object To see how to construct a callback function refer to Creating and Executing Callback Functions on page 5 51 or the example below Starting and Stopping a Digital 1 0 Object You use the start function to start a DIO object For example to start the digital I O object dio start dio After start is issued the Running property is automatically set to On and timer events can be generated If you attempt to start a digital I O object that does not contain any lines or that is already running an error is returned A digital I O object will stop executing under these conditions e The stop function is issued e An error occurred in the system When the device object stops Running is automatically set to
120. to daqhwinfo The supported vendors and adaptor names are given in The Hardware Driver Adaptor on page 2 7 For example to display hardware information for the winsound adaptor out daghwinfo winsound out AdaptorD11Name d v6 toolbox daq daq private mwwinsound d11 AdaptorDllVersion Version 2 2 R13 01 Jul 2002 AdaptorName winsound BoardNames AudioPCI Record InstalledBoardIds 0 ObjectConstructorName analoginput winsound 0 1x26 char The ObjectConstructorName field lists the subsystems supported by the installed sound cards and the syntax for creating a device object associated with a given subsystem To display the device object constructor names available for the AudioPCI Record board out ObjectConstructorName ans analoginput winsound 0O analogoutput winsound 0 This information tells you that the sound card supports analog input and analog output objects To create an analog input object for the sound card ai analoginput winsound To create an analog output object for the sound card ao analogoutput winsound Examining Your Hardware Resources Device Object Information To display hardware information for a specific device object you supply the device object as an argument to daqhwinfo The hardware information for the analog input object ai created in the preceding section is given below out out daqhwinfo ai AdaptorName Bits
121. up and ramp down rate Purpose For input channels RampRate is not generally used For source channels RampRate is usually used to ensure that the source signal starts and stops smoothly Characteristics Vendor Agilent Technologies Usage AO Channel Access Read write Data Type Double Read only Yes when running Values You can set RampRate to any value between 0 and 100 seconds 12 20 SourceMode Purpose Specify the source mode Description If SourceMode is set to Arbitrary the host program must provide the data to use for the arbitrary source signal Note that there is no Off source mode To turn a source channel off you must make it inactive When the source is inactive it is normally low impedance to ground To make the source high impedance set the SourceOutput property to Open Characteristics Vendor Agilent Technologies Usage AO Channel Access Read write Data Type String Read only Yes when running Values Arbitrary An arbitrary source signal See Also Properties SourceOutput 12 21 SourceOutput Purpose Description Characteristics 12 22 Specify the source output SourceOutput can be Normal Grounded Open CALOUT or SRC amp CALOUT If SourceOutput is Normal the normal source output is used This output is defined by the source mode and other source parameters If SourceOutput is Grounded the source output connector remains grounded while the source D A converter is internally connec
122. values from or write digital value to The collection of lines contained by a digital I O object Properties that are configured for individual lines A state of the Data Acquisition Toolbox where an analog input object stores acquired data to memory or a log file Any measurement that is not part of the phenomena of interest A timer chip on the hardware board which is programmed to generate a pulse train at the desired rate In most cases the onboard clock controls the sampling rate of the board Output range Postrigger data Precision Pretrigger data Properties Quantization Queuing data Running Sample rate Sampling Scanning hardware Sending Sensor Signal conditioning The span of output values for which a D A conversion is valid Data that is acquired and stored in the engine after the trigger event occurs A determination of how exactly a result is determined without reference to what the result means Data that is acquired and stored in the engine before the trigger event occurs A characteristic of the toolbox or the hardware driver that you can configure to suit your needs The property types supported by the toolbox include base properties device specific properties common properties and channel or line properties The process of converting an infinitely precise analog signal to a binary number This process is performed by an A D converter The process of storing data in the eng
123. when acquired data exceeds the valid hardware range Specify the M file callback function to execute when a run time error occurs Specify the M file callback function to execute every time a predefined number of samples is acquired for each channel group member Specify the number of samples to acquire for each channel group member before a samples acquired event is generated Specify the M file callback function to execute just before the device object starts running Specify the M file callback function to execute just after the device object stops running Specify the M file callback function to execute whenever a predefined period of time passes Specify the period of time between timer events Specify the M file callback function to execute when a trigger occurs Properties By Category Analog Input General Purpose Properties Buf feringConfig BufferingMode Channel EventLog Name Tag Timeout Type UserData Specify the per channel allocated memory Specify how memory is allocated Contain hardware channels added to the device object Store information for specific events Specify a descriptive name for the device object Specify a device object label Specify an additional waiting time to extract data Indicate the device object type Store data that you want to associate with a device object Channel Properties The analog input channel properties are given below
124. 0 1 2 instr Alternatively you can use the syntax AI analoginput hpe1432 1 2 0 See Also Functions addchannel daqhwinfo Properties Name 10 19 analogoutput Purpose Syntax Arguments Description Remarks 10 20 Create an analog output object AO analogoutput adaptor AO analogoutput adaptor 1D adaptor The hardware driver adaptor name The supported adaptors are hpe1432 keithley mcc nidaq parallel and winsound ID The hardware device identifier ID is optional if the device object is associated with a sound card having an ID of 0 AO The analog output object AO analogoutput adaptor creates the analog output object AO for a sound card having an ID of 0 adaptor must be winsound This is the only case where ID is not required AO analogoutput adaptor ID creates the analog output object AO for the specified adaptor and for the hardware device with device identifier ID ID can be specified as an integer or a string More About Creating Analog Output Objects e When an analog output object is created it does not contain any hardware channels To execute the device object hardware channels must be added with the addchannel function e You can create multiple analog output objects that are associated with a particular analog output subsystem However you can typically execute only one object at a time e The analog output object exists in the data acquisition en
125. 0 26 daqfind function 10 27 daqhelp function 10 29 daqhwinfo function 10 32 daqmem function 10 35 daqpropedit function 10 38 daqread function 10 40 daqregister function 10 44 daqreset function 10 45 daqschool function 10 46 daqsupport A 19 daqsupport function A 19 1 3 Index I 4 data extracting from engine 5 12 previewing 5 8 queuing for output 6 16 data acquisition session 3 1 3 2 acquiring data AI 4 12 adding channels AI object 4 3 AO object 6 3 adding lines 7 4 cleaning up 3 25 configuring properties AI object 4 8 AO object 6 5 creating a device object AI object 4 2 AO object 6 2 DIO object 7 2 loading 8 2 outputting data AO 6 8 saving 8 2 data block B 2 polling 5 10 data flow acquired data 2 4 output data 2 6 data missed event 5 46 data tips Oscilloscope 9 4 DataMissedFcn property 11 26 debugging your hardware A 19 daqsupport A 19 dec2binvec function 10 47 DefaultChannelValue property 11 27 delete function 10 49 demos 2 13 descriptive names channels 4 5 lines 7 10 device ID 4 2 device object 3 4 array 3 5 simultaneous input and output 6 37 configuring property values 3 18 copying 3 6 creating AI object 4 2 AO object 6 2 DIO object 7 2 invalid 3 7 loading 8 2 saving 8 2 specifying property names 3 19 starting 3 23 stopping 3 24 device specific properties 3 13 Agilent hardware 12 3 Keithley hardware 12 4 MCC hardware 12 5 NI hardware 12 5 parallel port 12 6 sound cards 12 6
126. 000 In addition to returning acquired data getdata can return relative time absolute time and event information As shown below data is an m by n array containing acquired data where m is the number of samples and n is the number of channels dy dig din do doo don d31 d32 dgn Extracted data Each column represents a separate input channel daa ding dmn getdata is considered a blocking function because it returns control to MATLAB only when the requested data is available Therefore samples are not missed or repeated When a trigger executes acquired data fills the engine When a getdata call is processed the requested samples are returned when the data is available and then extracted from the engine Managing Acquired Data As shown below if a fraction of the data stored in the engine is extracted then getdata always extracts the oldest data Time gt i Ga Extract the requested data I Data stored in engine If another getdata call is issued then once again the oldest samples are extracted Time gt 77 _ Extract the requested data I Data stored in engine Data extracted from the engine 5 13 5 Doing More with Analog Input Rules for Using getdata Using getdata to extract data stored in the engine follows these rules e If the requested number of samples is greater than the samples to be acquired then an er
127. 2 device specific 3 13 Agilent hardware 12 3 Keithley hardware 12 4 MCC hardware 12 5 NI hardware 12 5 parallel port 12 6 sound cards 12 6 line 3 12 DIO object 11 13 Oscilloscope channel 9 12 display 9 6 measurement 9 20 trigger 9 16 property values configuring 3 18 default 3 19 graphical property editor 3 20 saving 8 2 specifying names 3 19 propinfo function 10 80 putdata function 10 82 putsample function 10 84 putvalue function 10 85 Q quantization 1 19 queuing data for output 6 16 maximum number of samples 11 51 Quick Reference Guide 2 13 R RampRate property 12 20 reading digital values 7 14 read only properties 2 21 reference channels Oscilloscope 9 7 registering your adaptor A 18 relative time 5 17 repeating triggers 5 29 RepeatOutput property 11 60 resetting the hardware 10 45 retrieving data from a log file 8 7 returning property values dot notation 3 17 get 3 15 set function 3 14 running device objects 3 22 Running property 11 61 run time error event AI object 5 46 AO object 6 27 RuntimeErrorFcn property 11 62 S SampleRate property 11 64 samples acquired event 5 46 samples output event 6 27 samples per trigger postrigger data 5 27 pretrigger data 5 26 Index SamplesAcquired property 11 66 SamplesAcquiredFcn property 11 67 SamplesAcquiredFenCount property 11 68 SamplesAvailable property 11 69 SamplesOutput property 11 70 SamplesOutputFcn property 11 71 SamplesOutputFcnCount proper
128. 2 din ty dai d 22 don t2 d3i d32 dan t3 dint dm2 dmn tm 5 Doing More with Analog Input 5 18 Absolute Time To return data relative time information and the absolute time of the first trigger for the analog input object ai data time abstime getdata ai The absolute time is returned using the MATLAB clock format year month day hour minute seconds The absolute time from the getdata call is abstime abstime 1 0e 003 1 9990 0 0020 0 0190 0 0130 0 0260 0 0208 To convert the clock vector to a more convenient form t fix abstime sprintf d d d t 4 t 5 t 6 ans 13 26 20 The absolute time of the first trigger is also recorded by the InitialTriggerTime property Note that absolute times are recorded by the EventLog property for each trigger executed You can always find the absolute time associated with a data sample by adding its relative time to the absolute time of the associated trigger Refer to Recording and Retrieving Event Information on page 5 48 for more information about returning absolute time information with the EventLog property Configuring Analog Input Triggers Configuring Analog Input Triggers An analog input trigger is defined as an event that initiates data logging You can log data to the engine memory and to a disk file As shown in the figure below when a trigger occurs the Logging property is automatically set On and data is stored
129. 3 Span Purpose Description 12 24 Specify the measurement bandwidth in Hz For an input channel span specifies the maximum frequency at which valid alias protected data is received Frequencies above this value are filtered out For a source channel Span specifies the maximum frequency at which the output signal will correctly track the signal that the source is attempting to generate The valid values for Span depend of the current clock frequency You should set the clock frequency before setting Span Normally the maximum valid span is the clock frequency divided by 2 56 Valid spans are given by the maximum span divided by powers of two and the maximum span divided by five and by powers of two The ratio between the span and the maximum span is called the decimation factor For the E1432 module the maximum number of decimate by two passes allowed is nine Therefore the maximum decimation factor is 5 2 and the minimum valid span is clock frequency 2 56 5 2 If the clock frequency is larger than 51 2 kHz then the module is unable to do a decimation factor of one In this case the minimum decimation factor is two and the maximum valid span is clock frequency 5 12 For the E1433 module the maximum number of decimate by two passes allowed is 12 so the maximum decimation factor is 5 21 Because of limits in the module s DSP processor when the clock frequency is set higher than 102 400 Hz it is unable to do a
130. 5 4 13 Analog Input Examples 0 000 cece ees 4 14 Acquiring Data with a Sound Card 0000 4 14 Acquiring Data with a National Instruments Board 4 18 Evaluating the Analog Input Object Status 4 21 Status Properties osu 0 00 eee eens 4 21 The Display Summary 0 00 cece eee tenes 4 22 Doing More with Analog Input 5 Configuring and Sampling Input Channels 5 2 Input Channel Configuration 0 000 e ee eee 5 3 Sampling Rate 0 0 0 ccc eee ene ene 5 5 Channel Skew srian ax da bei La a are eg 5 6 iv Contents Managing Acquired Data 0 0 5 8 Previewing Data eero ori ar faa ca ees sw Ree hes Ba eae ee 5 8 Extracting Data from the Engine 00 5 12 Returning Time Information 0 000 e ee eee 5 17 Configuring Analog Input Triggers 5 19 Defining a Trigger Trigger Types and Conditions 5 20 Executing the Trigger 0 0 0 0 ccc tenes 5 25 Trigger Delays pra steed wae cae ae Dee RO wo APO wk 5 25 Repeating Triggers 0 cece eee eens 5 29 How Many Triggers Occurred 0000 e cece ene 5 35 When Did the Trigger Occur 0 0 0 0c cece ees 5 36 Device Specific Hardware Triggers 0 0000 ee ues 5 36 Events and Callbacks 0 0 0 0 c cece eee 5 45 Event Types sascha es POAT a RRR Doak ea Ree 5 45 Recording and Retr
131. 6 26 saving property values to a MAT file 8 2 Channel Editor GUI Channel Display pane 9 5 Channel pane 9 7 Channel Properties pane 9 13 Channel Exporter GUI 9 23 channel gain list 4 4 channel group AI object 4 3 AO object 6 3 channel names 4 6 Index channel properties 3 12 AI object 11 7 AO object 11 11 Channel property 11 18 channel skew 5 6 ChannelName property 11 20 channels 3 8 adding AI object 4 3 AO object 6 3 descriptive names 4 5 input configuration 5 3 mapping to hardware IDs 3 9 Oscilloscope hardware 9 2 math 9 7 reference 9 7 referencing 4 5 scan order 4 4 ChannelSkew property 11 21 ChannelSkewMode property 11 22 cleaning up the MATLAB environment clear function 3 25 daqfind function 10 49 delete function 3 25 clear function 10 24 clipping 6 35 clock function 5 36 clocked acquisition 1 22 ClockSource property 11 24 COLA property 12 10 common properties 3 12 AI object 11 3 AO object 11 8 DIO object 11 12 configuring property values dot notation 3 18 set function 3 18 constructor 3 4 Contents 2 12 continuous acquisition example using AI and AO 6 37 samples per trigger 5 22 trigger repeats 5 29 continuous output 6 21 Coupling property 12 11 creation function 3 4 custom adaptors 2 7 D D A converter 1 6 output range 6 34 sampling rate 6 5 daqcallback AI example 5 52 default property value data missed event AI 5 46 run time error event AI object 5 46 AO object 6 27 daqcallback function 1
132. 8 3 Configure property values Define a 2 second acquisition and configure a software trigger The source of the trigger is chan and the trigger executes when a rising voltage level has a value of at least 0 2 volt Additionally 500 pretrigger samples are collected duration 2 two second acquisition set AIVoice SampleRate 44100 ActualRate get AlIVoice SampleRate set AIVoice SamplesPerTrigger ActualRate duration set AIVoice TriggerChannel chan set AIVoice TriggerType Software set AIVoice TriggerCondition Rising set AIVoice TriggerConditionValue 0 2 set AIVoice TriggerDelayUnits Samples set AIVoice TriggerDelay 500 Acquire data Start AlVoice acquire the specified number of samples and extract the first 1000 samples from the engine as sample time pairs start AlVoice data time getdata AIVoice 1000 Plot all the extracted data plot time data xlabel Time sec ylabel Signal Level Volts grid on Make sure AlVoice has stopped running before cleaning up the workspace waittilstop AIVoice 2 Clean up When you no longer need AIVoice you should remove it from memory and from the MATLAB workspace delete AIVoice clear AIVoice Configuring Analog Input Triggers The output from this example is shown below Note that the pretrigger data constitutes half of the 1000 samples extracted from the engine Addit
133. Also Specify the M file callback function to execute every time a predefined number of samples is output for each channel group member A samples output event is generated immediately after the number of samples specified by the SamplesOutputFcnCount property is output for each channel group member This event executes the callback function specified for SamplesOutputFcn Samples output event information is not stored in the EventLog property Usage AO Common Access Read write Data type String Read only No when running The default value is an empty string Properties EventLog SamplesOutputFcnCount 11 71 SamplesOutputFcnCount Purpose Description Characteristics Values See Also 11 72 Specify the number of samples to output for each channel group member before a samples output event is generated A samples output event is generated immediately after the number of samples specified by SamplesOutputFcnCount is output for each channel group member This event executes the callback function specified by the SamplesOutputFen property Usage AO Common Access Read write Data type Double Read only Yes when running The default value is 1024 Properties SamplesOutputFecn SamplesPerTrigger Purpose Description Characteristics Values Example See Also Specify the number of samples to acquire for each channel group member for each trigger that occurs SamplesPerTrigger specifies the
134. Analog Input Channel Properties ChannelName HwChannel Index InputRange NativeOffset NativeScaling Specify a descriptive channel name Specify the hardware channel ID Indicate the MATLAB index of a hardware channel Specify the range of the analog input subsystem Indicate the offset to use when converting between the native data format and doubles Indicate the scaling to use when converting between the native data format and doubles 11 bs Property Referenc Analog Input Channel Properties Continued Parent Indicate the parent device object of a channel SensorRange Specify the range of data you expect from your sensor Type Indicate a channel Units Specify the engineering units label UnitsRange Specify the range of data as engineering units Analog Output Properties Analog output base properties are divided into two main categories common properties and channel properties Common properties apply to every channel contained by the analog output object while channel properties can be configured for individual channels Common Properties The analog output common properties are grouped into the following categories based on usage Analog Output Basic Setup Properties SampleRate Specify the per channel rate at which digital data is converted to analog data TriggerType Specify the type of trigger to execute Analog Output Trigger Properties InitialTrigger Indic
135. CALIN line Ground the input Select the module s CALIN line via the CAL connection in a break out box NumMuxBoards Purpose Description Characteristics Values Specify the number of external multiplexer devices connected NumMuxBoards specifies the number of AMUX 64T multiplexer devices connected to your hardware NumMuxBoards can be 0 1 2 or 4 If you are using a 1200 Series board then NumMuxBoards can only be 0 Vendor Usage Access Data type Read only when running 0 1 2 or 4 National Instruments AI Common Read write Double No The number of AMUX 64T multiplexer devices connected 12 17 OutOfDataMode Purpose Description Characteristics Values Example See Also 12 18 Specify how the value held by the analog output subsystem is determined When queued data is output to the analog output AO subsystem the hardware typically holds a value For National Instruments and Measurement Computing devices the value held is determined by OutOfDataMode OutOfDataMode can be Hold or DefaultValue If OutOfDataMode is Hold then the last value output is held by the AO subsystem If OutOfDataMode is DefaultValue then the value specified by the DefaultChannelValue property is held by the AO subsystem Vendor Keithley Measurement Computing National Instruments Usage AO Common Access Read write Data type String Read only Yes when running Hold Hold the last output
136. Callback Functions 6 31 Linearly Scaling the Data Engineering Units 6 34 Example Performing a Linear Conversion 6 35 Starting Multiple Device Objects 6 37 7 Creating a Digital I O Object 00050 7 2 The Parallel Port sicrie re curii cece ene 7 3 Adding Lines to a Digital I O Object 7 4 Line and Port Characteristics 0 00 0 e eee ences 7 5 Referencing Individual Hardware Lines 7 9 Writing and Reading Digital I O Line Values 7 12 Writing Digital Values 0 0 0 ccc ene 7 12 Reading Digital Values 0 c cece eee 7 14 Example Writing and Reading Digital Values 7 15 Generating Timer Events 0000 e eee 7 17 Timer EVEntS resectie e352 gatbnees toa EE Pease esa 7 17 Starting and Stopping a Digital I O Object 7 18 Example Generating Timer Events 0000 7 19 Evaluating the Digital I O Object Status 7 20 The Display Summary 0 00 c cece eens 7 20 Saving and Loading the Session 8 Saving and Loading Device Objects 8 2 Saving Device Objects to an M File 2005 8 2 Saving Device Objects toa MAT File 8 4 Logging Information to Disk 000 8 5 Specifying a Filename 0 0 cece eee eee 8 6 Retrieving Logged I
137. Channel Scaling ShowName pE True VerticalOffsetSensitivity 0 006 VerticalScaleSensitivity 0 01 OK Cancel Help lick Help to view property descriptions Scaling the Channel Data Channel Properties You can change the characteristics of the hardware math and reference channels that are listed in the panel by configuring their channel properties You can access the channel properties these two ways e Property Inspector Place the mouse cursor in the Channel Scaling panel right click and select Edit Properties from the menu e Channel Editor GUI Select Channel from the Edit menu and then choose the Channel Properties pane For this example use the Channel Editor GUI to modify the marker characteristics for both CHO and CH1 The steps are 1 Select both hardware channels from the Select the channels list box 2 Specify a circular symbol for the Marker property and specify an interval of 4 for the MarkerInterval property The Channel Properties pane is shown below Channel Editor xj Channel Channel Properties Channel Display Selectthe channels Select both channels Editthe selected channels properties BufferSize 100000 Color ce Marker zo Specify a circular marker symbol MarkerEdgeColor iz MarkerFaceColor a Markerinterval 4 Specify a marker interval of 4 MarkerSize 6 Name Mixed L ShowAsScientific False ShowIndicator PE True X
138. Data Acquisition Toolbox For Use with MATLAB Computation Visualization Programming T User s Guide The MathWorks Version 2 X C o How to Contact The MathWorks www mathworks com comp soft sys matlab support mathworks com suggest mathworks com bugs mathworks com doc mathworks com service mathworks com info mathworks com 508 647 7000 508 647 7001 The MathWorks Inc Web Newsgroup Technical support Product enhancement suggestions Bug reports Documentation error reports Order status license renewals passcodes Sales pricing and general information Phone Fax Mail 3 Apple Hill Drive Natick MA 01760 2098 For contact information about worldwide offices see the MathWorks Web site Data Acquisition Toolbox User s Guide COPYRIGHT 1999 2002 by The MathWorks Inc The software described in this document is furnished under a license agreement The software may be used or copied only under the terms of the license agreement No part of this manual may be photocopied or repro duced in any form without prior written consent from The MathWorks Inc FEDERAL ACQUISITION This provision applies to all acquisitions of the Program and Documentation by or for the federal government of the United States By accepting delivery of the Program the government hereby agrees that this software qualifies as commercial computer software within the meaning of FAR Part 12 212 DFA
139. GIN line or when the analog input signal rises above the value given in StopTriggerConditionValue Falling Trigger on the falling edge of TGIN line or when the analog input signal falls below the value given in StopTriggerConditionValue See Also Properties StopTriggerChannel StopTriggerConditionValue StopTriggerDelay StopTriggerType 12 29 StopTriggerConditionValue Purpose Description Characteristics Values See Also 12 30 Specify a value for the stop trigger condition StopTriggerConditionValue defines the value that must be satisfied before a stop trigger executes You use this property only when StopTriggerType is set to HwAnalog Vendor Keithley Usage AI Common Access Read write Data Type Double Read only Yes when running The default value is 0 Properties StopTriggerChannel StopTriggerCondition StopTriggerDelay StopTriggerType StopTriggerDelay Purpose Description Characteristics Values See Also Specify the delay value for a stop trigger StopTriggerDelay allows the acquisition to continue beyond a hardware stop trigger event The property value is interpreted in StopTriggerDelayUnits which can be either seconds or samples StopTriggerDelay must be zero the default or a positive number Negative pretrigger delays are not supported Vendor Keithley Usage AI Common Access Read write Data Type Double Read only Yes when running The default value is 0 Onl
140. ID can be specified as an integer or a string More About Creating Analog Input Objects e When an analog input object is created it does not contain any hardware channels To execute the device object hardware channels must be added with the addchannel function e You can create multiple analog input objects that are associated with a particular analog input subsystem However you can typically execute only one object at a time e The analog input object exists in the data acquisition engine and in the MATLAB workspace If you create a copy of the device object it references the original device object in the engine e If ID is a numeric value then you can specify it as an integer or a string If ID contains any nonnumeric characters then you must specify it as a string see the Agilent Technologies example below e The Name property is automatically assigned a descriptive name that is produced by concatenating adaptor ID and AI You can change this name at any time 10 17 analoginput Example 10 18 More About the Hardware Device Identifier When data acquisition devices are installed they are assigned a unique number which identifies the device in software The device identifier is typically assigned automatically and can usually be manually changed using a vendor supplied device configuration utility National Instruments refers to this number as the device number while Agilent Technologies refers to it is as the
141. InputType 11 41 Line 11 43 LineName 11 44 LogFileName 11 45 Logging 11 46 LoggingMode 11 47 LogToDiskMode 11 48 ManualTriggerHwOn 11 49 MaxSamplesQueued 11 51 Name 11 52 NativeOffset 11 53 NativeScaling 11 55 NumMuxBoards 12 17 OutOfDataMode 12 18 OutputRange 11 56 Parent 11 58 Port 11 59 PortAddress 12 19 RampRate 12 20 RepeatOutput 11 60 Running 11 61 RuntimeErrorFen 11 62 SampleRate 11 64 SamplesAcquired 11 66 SamplesAcquiredFcn 11 67 SamplesAcquiredFenCount 11 68 SamplesAvailable 11 69 SamplesOutput 11 70 SamplesOutputFcen 11 71 SamplesOutputFenCount 11 72 SamplesPerTrigger 11 73 Sending 11 74 SensorRange 11 75 SourceMode 12 21 SourceOutput 12 22 Span 12 24 StandardSampleRates 12 26 StartFen 11 76 StopFen 11 77 StopTriggerChannel 12 27 StopTriggerCondition 12 28 StopTriggerConditionValue 12 30 StopTriggerDelay 12 31 StopTriggerDelayUnits 12 32 StopTriggerType 12 33 Sum 12 34 Tag 11 79 Timeout 11 80 TimerFcn 11 81 TimerPeriod 11 82 TransferMode 12 35 TriggerChannel 11 84 TriggerCondition 11 85 TriggerConditionValue 11 90 TriggerDelay 11 91 TriggerDelayUnits 11 92 TriggerFcn 11 83 TriggerRepeat 11 93 TriggersExecuted 11 94 TriggerType 11 95 Type 11 98 Units 11 99 Index UnitsRange 11 100 UserData 11 101 property characteristics 2 21 Property Editor 3 20 property types base 3 13 channel 3 12 AI object 11 7 AO object 11 11 common 3 12 AI object 11 3 AO object 11 8 DIO object 11 1
142. LogFileName as long as it conforms to the MATLAB naming conventions the name cannot start with a number and cannot contain spaces If no extension is specified as part of LogFileName then daq is used The default value for LogFileName is logfile daq You can choose whether an output file is overwritten or if multiple log files are created with the LogToDiskMode property Setting LogToDiskMode to Overwrite causes the output file to be overwritten Setting LogToDiskMode to Index causes new data files to be created each with an indexed name based on the value of LogFileName Characteristics Usage AI Common Access Read write Data type String Read only Yes when running Values The default value is logfile daq See Also Properties Logging LoggingMode LogToDiskMode 11 45 Logging Purpose Description Characteristics Values See Also 11 46 Indicate whether data is being logged to memory or to a disk file Along with the Running property Logging reflects the state of an analog input object Logging can be On or Off Logging is automatically set to On when a trigger occurs When Logging is On acquired data is being stored in memory or to a disk file Logging is automatically set to Off when the requested samples are acquired an error occurs or a stop function is issued When Logging is Off you can still preview data with the peekdata function provided Running is On However peekdata does not guarantee that all
143. M file callback function to execute when a run time error occurs Specify the M file callback function to execute every time a predefined number of samples is output for each channel group member Specify the number of samples to output for each channel group member before a samples output event is generated Specify the M file callback function to execute just before the device object starts running Specify the M file callback function to execute just after the device object stops running Specify the M file callback function to execute whenever a predefined period of time passes Specify the period of time between timer events Specify the M file callback function to execute when a trigger occurs 11 10 Properties By Category Analog Output General Purpose Properties BufferingConfig BufferingMode Channel EventLog Name OutOfDataMode Tag Type UserData Specify the per channel allocated memory Specify how memory is allocated Contain hardware channels added to the device object Store information for specific events Specify a descriptive name for the device object Specify how the value held by the analog output subsystem is determined Specify a device object label Indicate the device object type Store data that you want to associate with a device object Channel Properties The analog output channel properties are given below Analog Output Channel Properties
144. MATLAB command line 1 Create a device object Create the analog output object AO for a National Instruments board The installed adaptors and hardware IDs are found with daqhwinfo AO analogoutput nidaq 1 2 Add channels Add one channel to AO chan addchannel A0 0 6 Analog Output 3 Configure property values Define an output time of four seconds assign values to the basic setup properties generate data to be queued and queue the data with one call to putdata duration 4 set AO SampleRate 10000 set AO TriggerType Manual ActualRate get AO SampleRate len ActualRate duration data sin linspace 0 2 pi 500 1len putdata AO data Output data Start AO issue a manual trigger and wait for the device object to stop running start AO trigger AO waittilstop A0 5 Clean up When you no longer need AO you should remove it from memory and from the MATLAB workspace delete A0O clear AO Getting Started with Analog Output Evaluating the Analog Output Object Status You can evaluate the status of an analog output AO object by e Returning the values of certain properties e Invoking the display summary Status Properties The properties associated with the status of your analog output object allow you to evaluate e If the device object is running e If data is being output from the engine e How much data is queued in the engine e How much data h
145. Most data acquisition devices possess the ability to accept a hardware trigger Hardware triggers are processed directly by the hardware and are typically transistor transistor logic TTL signals Hardware triggers are used when speed is required because a hardware device can process an input signal much faster than software The device specific hardware triggers are presented to you as additional property values Hardware triggers for National Instruments and Agilent Technologies devices are discussed below and in Chapter 11 Base Property Reference Note that the available hardware trigger support depends on the board you are using Refer to your hardware documentation for detailed information about its triggering capabilities National Instruments When using National Instruments hardware there is an additional analog output trigger type available to you digital triggering If TriggerType is set to HwDigital the trigger is given by an external TTL signal that is input directly into the hardware device The following example illustrates how to configure a hardware digital trigger ao analogoutput nidaq 1 addchannel ao 0 1 set ao TriggerType HwDigital With this trigger configuration ao will not start outputting data until the TTL signal is detected by the hardware on the appropriate pin Configuring Analog Output Triggers The diagram below illustrates how you can connect a digital trigger signal to an
146. NaN is included in the data stream e You can specify data as the native data type of the hardware Note that MATLAB supports math operations only for the double data type Therefore to use math functions on native data you must convert it to doubles e If the output data is not within the range specified by the OutputRange property then the data is clipped putdata Example See Also e The SamplesOutput property keeps a running count of the total number of samples that have been output per channel e The SamplesAvailable property tells you how many samples are ready to be output from the engine per channel After data is output SamplesAvailable is automatically reduced by the number of samples sent to the hardware Create the analog output object ao for a National Instruments board add two output channels to it and generate 10 seconds of data to be output ao analogoutput nidaq 1 ch addchannel ao 0 1 set ao SampleRate 1000 data linspace 0 1 10000 Before you can output data it must be queued in the engine using putdata putdata ao data data start ao Functions putsample Properties MaxSamplesQueued OutputRange RepeatOutput SamplesAvailable SamplesOutput Timeout UnitsRange 10 83 putsample Purpose Syntax Arguments Description Remarks Example See Also 10 84 Immediately output one sample putsample obj data obj An analog output object data The da
147. O isvalid Determine if device objects channels or lines are valid V length Return the length of a device object channel group or y line group load Load device objects channels or lines into the MATLAB V y y workspace makenames Generate a list of descriptive channel or line names y V muxchanidx Return multiplexed scanned channel index obj2mfile Convert device objects channels or lines to MATLAB y y code save Save device objects to a MAT file V showdaqevents Display event log information size Return the size of a device object channel group or line y group Functions Alphabetical List Functions Alphabetical List This section contains detailed descriptions of all toolbox functions Each function reference page contains some or all of this information e The function name e The purpose of the function e The function syntax All valid input argument and output argument combinations are shown In some cases an ellipsis is used for the input arguments This means that all preceding input argument combinations are valid for the specified output argument s e A description of each argument e A description of the function e Additional remarks about usage e An example of usage e Related functions or properties 10 7 addchannel Purpose Add hardware channels to an analog input or analog output object Syntax chans addchannel obj hwch chans addchannel obj hwch index chans a
148. O only Keithley HwDigital The trigger source is an external digital signal AI only Pretrigger data cannot be captured Measurement Computing HwDigital The trigger source is an external digital signal AI only Pretrigger data cannot be captured HwAnalog The trigger source is an external analog signal AI only National Instruments HwDigital The trigger source is the falling edge of an external digital signal Pretrigger data cannot be captured HwAnalogChannel The trigger source is an external analog signal AI only HwAnalogPin The trigger source is a low range external analog signal AI only For 1200 Series hardware HwDigital is the only device specific TriggerType value for analog input subsystems Analog output subsystems do not support any device specific TriggerType values 11 96 TriggerType See Also Functions start trigger Properties Logging Sending TriggerCondition TriggerConditionValue 11 97 Type Purpose Description Characteristics Values 11 98 Indicate the device object type a channel or a line Type is associated with device objects channels and lines For device objects Type can be Analog Input Analog Output or Digital I 0 Once a device object is created the value of Type is automatically defined For channels the only value of Type is Channel For lines the only value of Type is Line The value is automatically defined when channels or lines are
149. RS Part 227 7202 1 DFARS Part 227 7202 3 DFARS Part 252 227 7013 and DFARS Part 252 227 7014 The terms and conditions of The MathWorks Inc Software License Agreement shall pertain to the government s use and disclosure of the Program and Documentation and shall supersede any conflicting contractual terms or conditions If this license fails to meet the government s minimum needs or is inconsistent in any respect with federal procurement law the government agrees to return the Program and Documentation unused to MathWorks MATLAB Simulink Stateflow Handle Graphics and Real Time Workshop are registered trademarks and TargetBox is a trademark of The MathWorks Inc Other product or brand names are trademarks or registered trademarks of their respective holders Printing History May 1999 First printing New for Version 1 November 2000 Second printing Revised for Version 2 Release 12 June 2001 Third printing Revised for Version 2 1 Release 12 1 July 2002 Online only Revised for Version 2 2 Release 13 Preface What Is the Data Acquisition Toolbox xii Exploring the Toolbox 0 0 0 0 0 ccc ee eens xii Related Products 0 0 xiii Using This Guide 0 0 ccc cee eee xiv Expected Background 0 0 ce cece eee ne eens xiv Using the Documentation Examples 000000 xV How This Guide Is Organized 0 ccc eee xv Installation Information
150. The serial number of the device 5 10 4 4 Version 1 1 Build 51 Version 1 3 1 A Troubleshooting Your Hardware A 10 Is Your Hardware Functioning Properly To troubleshoot your National Instruments hardware you should use the Test Panel The Test Panel allows you to test each subsystem supported by your board and is installed as part of the NI DAQ driver software You can access the Test Panel by right clicking the appropriate device in the Measurement amp Automation Explorer and choosing Test Panel For example suppose you want to verify that the analog input subsystem on your PCI 6024E board is operating correctly To do this you should connect a known signal such as that produced by a function generator to one or more channels using a screw terminal panel The result of such a test is shown below for channel 1 Test Panel BE einstrumes Device Name Device Number INSTRUMENTS PCr6024E fi Analog Input Analog Output Counter 1 0 Digital 1 0 Channel 1 4 0000 Input Limits High 100000 Last Error Low 10 0000 0 0000 Sample Rate Hz m Eror 10000 0 Error Codes Ener Codes Stop 399 Data Mode Strip Cha r Average Reading Gre Sho 0 099336 Continuo C Full Range If the Test Panel does not provide you with the expected results for the subsystem under test and you are sure t
151. The slowest but most common method to move acquired data to system memory is for the board to generate an interrupt request IRQ signal This signal can be generated when one sample is acquired or when multiple samples The Analog Input Subsystem are acquired The process of transferring data to system memory via interrupts is given below 1 When data is ready for transfer the CPU stops whatever it is doing and runs a special interrupt handler routine that saves the current machine registers and then sets them to access the board 2 The data is extracted from the board and placed into system memory 3 The saved machine registers are restored and the CPU returns to the original interrupted process The actual data move is fairly quick but there is a lot of overhead time spent saving setting up and restoring the register information Therefore depending on your specific system transferring data by interrupts might not be a good choice when the sampling rate is greater than around 5 kHz DMA Direct memory access DMA is a system whereby samples are automatically stored in system memory while the processor does something else The process of transferring data via DMA is given below 1 When data is ready for transfer the board directs the system DMA controller to put it into in system memory as soon as possible 2 As soon as the CPU is able which is usually very quickly it stops interacting with the data acquisition hardwa
152. Time delta abs aotime aitime sprintf d delta 6 ans 2 28881 8e 005 Note that this number depends on the specific platform you are using To stop both device objects stop ai ao The output from daqcallback is shown below Stop event occurred at 13 00 25 for the object winsound0O AO Stop event occurred at 13 00 25 for the object winsoundO AI Digital Input Output Digital I O DIO subsystems are designed to transfer digital values to and from hardware These values are handled either as single bits or lines or as a port which typically consists of eight lines While most popular data acquisition boards include some DIO capability it is usually limited to simple operations and special dedicated hardware is required for performing advanced DIO operations The Data Acquisition Toolbox provides access to digital I O subsystems through a digital I O object The DIO object can be associated with a parallel port or with a DIO subsystem on a data acquisition board The purpose of this chapter is to show you how to perform data acquisition tasks using your digital I O hardware The sections are as follows Creating a Digital I O Create a MATLAB object that represents the digital I O subsystem Object p 7 2 Adding Lines to a Digital Associate hardware lines with the digital I O object I O Object p 7 4 Writing and Reading Digital Write values to digital lines and read value from digital lines I O Line Values
153. TimerPeriod Purpose Description Characteristics Values See Also 11 82 Specify the period of time between timer events TimerPeriod specifies the time in seconds that must pass before the callback function specified for TimerFcn is called Time is measured relative to when the hardware device starts running Some timer events might not be processed if your system is significantly slowed or if the TimerPeriod value is too small For example a common application for timer events is to display data However because displaying data is a CPU intensive task some of these events might be dropped Usage AI AO DIO Common Access Read write Data type Double Read only No when running The default value is 0 1 second Properties TimerFen TriggerFcn Purpose Description Characteristics Values See Also Specify the M file callback function to execute when a trigger occurs A trigger event is generated immediately after a trigger occurs This event executes the callback function specified for TriggerFcn Under most circumstances the callback function is not guaranteed to complete execution until sometime after Logging is set to On for analog input AI objects or Sending is set to On for analog output AO objects Trigger event information is stored in the Type and Data fields of the EventLog property The Type field value is Trigger The Data field values are given below Data Field Value Des
154. UND specific properties BitsPerSample StandardSampleRates Off On To return all common properties and their current values for a device object you must supply the device object to get For example all common properties for ai are shown below The base properties are listed first followed by the device specific properties get ai BufferingConfig 512 30 BufferingMode Auto Channel 2x1 aichannel ChannelSkew 0 ChannelSkewMode None ClockSource Internal DataMissedFcn daqcallback EventLog InitialTriggerTime 00000 0 InputOverRangeFcn InputType AC Coupled LogFileName logfile daq Logging Off LoggingMode Memory LogToDiskMode Overwrite 3 15 3 The Data Acquisition Session 3 16 ManualTriggerHwOn Start Name winsound0 AI Running Off RuntimeErrorFcn daqcallback SampleRate 8000 SamplesAcquired 0 SamplesAcquiredFcn SamplesAcquiredFcnCount 1024 SamplesAvailable 0 SamplesPerTrigger 8000 StartFen StopFcn Tag Timeout 1 TimerFen TimerPeriod 0 1 TriggerFen TriggerChannel 1x0 aichannel TriggerCondition None TriggerConditionValue 0 TriggerDelay 0 TriggerDelayUnits Seconds TriggerRepeat 0 TriggersExecuted 0 TriggerType Immediate Type Analog Input UserData WINSOUND specific properties BitsPerSample 16 StandardSampleRates On To display the current value for one property you supply the property name
155. Usage AI Common Access Read write Data type Double Read only Yes when running The default value is zero Functions disp stop Properties TriggersExecuted TriggerType 11 93 TriggersExecuted Purpose Description Characteristics Values Example See Also 11 94 Indicate the number of triggers that execute You can find out how many triggers executed by returning the value of TriggersExecuted The trigger number for each trigger executed is also recorded by the Data Trigger field of the EventLog property Usage AI AO Common Access Read only Data type Double Read only N A when running The default value is zero Create the analog input object ai and add one channel to it ai ch analoginput winsound addchannel ai 1 Configure ai to acquire 40 000 samples with five triggers using the default sampling rate of 8000 Hz set ai TriggerRepeat 4 start ai TriggersExecuted returns the number of triggers executed ai TriggersExecuted ans 5 Properties EventLog TriggerType Purpose Specify the type of trigger to execute Description TriggerType can be Immediate Manual or Software If TriggerType is Immediate the trigger occurs immediately after the start function is issued If TriggerType is Manual the trigger occurs immediately after the trigger function is issued If TriggerType is Software the trigger occurs when the associated trigger condition is satisfied
156. Value A property value obj Channel index One or more channels contained by obj obj Line index One or more lines contained by obj Actual The actual value for the specified property Actual setverify obj PropertyName PropertyValue sets PropertyName to PropertyValue for obj and returns the actual property value to Actual Actual setverify obj Channel index PropertyName PropertyValue sets PropertyName to PropertyValue for the channels specified by index and returns the actual property value to Actual Actual setverify obj Line index PropertyName PropertyValue sets PropertyName to PropertyValue for the lines specified by index and returns the actual property value to Actual setverify is equivalent to the commands set obj PropertyName PropertyValue Actual get obj PropertyName Using setverify is not required for setting property values but it does provide a convenient way to verify the actual property value set by the data acquisition engine setverify Example See Also setverify is particularly useful when setting the SampleRate InputRange and OutputRange properties because these properties can only be set to specific values accepted by the hardware You can use the propinfo function to obtain information about the valid values for these properties If a property value is specified but does not match a valid value then e If the specified value is within the range of supp
157. Window Help o gt GA A sxf z e ai axi 1332 analoginput object Display Summary o Call Property Editor Select All cea Access context pop up menus Display Hard Inf oan s _inport Dita ENA a j by right clicking a device object Save Selection As Save Workspace As DAG Help Copy Delete Clear Workspace Rename daqpropedit Example Create the analog input object ai for a sound card and add two channels ai analoginput winsound addchannel ai 1 2 To configure property values for ai using daqpropedit daqpropedit ai The Data Acquisition Property Editor is shown below File Options Help List of device objects channels and lines f BitsPerS ample IE Property to configure and its current value Buffering onfig 512 30 Bufferingtlode Auto 2x1 aichannel Do List of configurable properties None Internal and their current values DatallissedAction dagaction EventLog double Default Value fe Constraint Bounded Constraint Value 3 16 p wa m Read Only 0 False ReadOnywhen imu Property characteristics Device Specific 7 Running a True BITSPERSAMPLE 16 BitsPerSample specifies the number of bits the sound card uses to each sampla Property help The value of BitsPerSample cannot ke modified while the object is v See Also Functions daqfind daqhel
158. able to use the toolbox to configure your own analog input session The sections are as follows Creating an Analog Input Create a MATLAB object that represents the analog input subsystem Object p 4 2 Adding Channels to an Associate hardware channels with the analog input object Analog Input Object p 4 3 Configuring Analog Input Define the object behavior by assigning values to properties Properties p 4 8 Acquiring Data p 4 12 Execute the object and stream data from the hardware channels to memory Analog Input Examples Examples that show you how to perform a complete data acquisition p 4 14 task Evaluating the Analog Input Return the values of certain properties in a convenient display format Object Status p 4 21 4 Getting Started with Analog Input 4 2 Creating an Analog Input Object You create an analog input object with the analoginput function analoginput accepts the adaptor name and the hardware device ID as input arguments For a list of supported adaptors refer to The Hardware Driver Adaptor on page 2 7 The device ID refers to the number associated with your board when it is installed Some vendors refer to the device ID as the device number or the board number The device ID is optional for sound cards with an ID of 0 Use the daqhwinfo function to determine the available adaptors and device IDs Each analog input object is associated with one board and one analog input subsystem For example
159. ack functions allow you to easily display information stored in the EventLog property You can run this example by typing daqdoc6_5 at the MATLAB command line The local callback function daqdoc6_5disp not shown below displays the absolute time and relative sample associated with the start trigger and stop events 1 Create a device object Create the analog output object AO for a sound card The installed adaptors and hardware IDs are found with daqhwinfo AO analogoutput winsound AO analogoutput nidaq 1 AO analogoutput mcc 1 X 2 Add channels Add one channel to AO chan addchannel A0 1 chan addchannel A0 0 For NI and MCC 3 Configure property values Specify daqdoc6_5disp as the M file callback function to execute when the start trigger and stop events occur generate data to be queued and queue the data with one call to putdata set AO SampleRate 8000 ActualRate get AO SampleRate set A0O StartFcn daqdoc6_5disp set A0O TriggerFcn daqdoc6_5disp set A0O StopFcn daqdoc6_ 5disp data sin linspace 0 2 pi 500 ActualRate data data data data Events and Callbacks time length data AO SampleRate putdata AO data Output data Start AO The waittilstop function blocks the MATLAB command line and waits for AO to stop running start AO waittilstop A0 5 Clean up When you no longer need AO you should remove it from memory
160. acquired sample number when the event occurred Channel The index of the channel that experienced an overrange signal OverRange Indicates if the channel went from overrange to in range or from in range to overrange Usage AI Common Access Read write Data type String Read only No when running The default value is an empty string Properties EventLog InputRange InputRange Purpose Description Specify the range of the analog input subsystem InputRange is a two element vector that specifies the range of voltages that can be accepted by the analog input AI subsystem You should configure InputRange so that the maximum dynamic range of your hardware is utilized If an input signal exceeds the InputRange value then an overrange condition occurs Overrange detection is enabled only if the analog input object is running and a value is specified for the InputOverRangeFcn property For many devices the input range is expressed in terms of the gain and polarity AI subsystems have a finite number of InputRange values that you can set If an input range is specified but does not match a valid range then the next highest supported range is automatically selected by the engine If InputRange exceeds the range of valid values then an error is returned Use the daqhwinfo function to return the input ranges supported by your board Because the engine can set the input range to a value that differs from the value you spe
161. after an error occurs M File Functions To perform any task with your data acquisition application you must call M file functions from the MATLAB environment Among other things these functions allow you to e Create device objects which provide a gateway to your hardware s capabilities and allow you to control the behavior of your application e Acquire or output data e Configure property values e Evaluate your acquisition status and hardware resources For a listing of all Data Acquisition Toolbox functions refer to Chapter 10 Function Reference You can also display all the toolbox functions by typing help daq 2 3 2 Getting Started with the Data Acquisition Toolbox 2 4 The Data Acquisition Engine The data acquisition engine or just engine is a MEX file dynamic link library DLL file that e Stores the device objects and associated property values that control your data acquisition application e Controls the synchronization of events e Controls the storage of acquired or queued data While the engine performs these tasks you can use MATLAB for other tasks such as analyzing acquired data In other words the engine and MATLAB are asynchronous The relationship between acquiring data outputting data and data flow is described below The Flow of Acquired Data Acquiring data means that data is flowing from your hardware device into the data acquisition engine where it is temporarily stored in mem
162. ake measurements on acquired data using predefined or custom p 9 17 measurement types Exporting Data p 9 23 Save channel data or measurements to the workspace a figure or a MAT file Saving and Loading the Save and load the hardware configuration the property values and Oscilloscope Configuration the state of the Oscilloscope p 9 25 This examples in this chapter use Measurement Computing s Demo Board which is installed with InstaCal or the Universal Library driver The Demo Board is a software simulation of an 8 channel 16 bit analog input device You can associate waveforms such as a sine wave or a square wave or input from a data file with the analog input channels You can download InstaCal or the Universal Library driver from http www measurementcomputing com 9 softscope The Data Acquisition Oscilloscope 9 2 Opening the Oscilloscope To open the Oscilloscope create an analog input object for the Measurement Computing Demo Board add two hardware channels and supply the object to the softscope function ai analoginput mcc 0 addchannel ai 0 1 softscope ai As shown below the Oscilloscope opens with a single display containing a marker for each added hardware channel a channel scaling panel and a trigger panel Oscilloscope lol xi File Edit Help Channel Scaling Triggers Horizontal Acquire Continuous gt sel Scale Offset Samples to acquire J Fillthe display C C
163. al has its own ground reference which is tied to the negative input of the instrumentation amplifier Sound Cards AC Coupled The input is coupled so that constant DC signal levels are suppressed 11 42 Line Purpose Description Characteristics Values Example See Also Contain hardware lines added to the device object Line is a vector of all the hardware lines contained by a digital I O DIO object Because a newly created DIO object does not contain hardware lines Line is initially an empty vector The size of Line increases as lines are added with the addline function and decreases as lines are removed with the delete function You can use Line to reference one or more individual lines To reference a line you must know its MATLAB index and hardware ID The MATLAB index is given by the Index property while the hardware ID is given by the HwLine property Usage DIO Common Access Read write Data type Vector of lines Read only Yes when running Values are automatically defined when lines are added to the DIO object with the addline function The default value is an empty column vector Create the digital I O object dio and add four input lines to it dio digitalio nidaq 1 addline dio 0 3 In To set a property value for the first line added ID 0 you can reference the line by its index using the Line property linei dio Line 1 set line1 Direction Out Functions addlin
164. ally defined when channels are added to the device object with the addchannel function The default value is one Create the analog input object ai for a National Instruments board and add the first three hardware channels to it ai analoginput nidaq 1 addchannel ai 0 2 11 31 HwChannel See Also 11 32 Based on the current configuration the hardware channels are scanned in order from 0 to 2 To swap the scan order of channels 0 and 1 you can assign these channels to the appropriate indices using HwChannel ai Channel 1 HwChannel 1 ai Channel 2 HwChannel 0 Functions addchannel Properties Channel Index HwLine Purpose Description Characteristics Values Example See Also Specify the hardware line ID All lines contained by a digital I O object have a hardware ID and an associated MATLAB index The hardware ID is given by HwLine and the MATLAB index is given by the Index property The HwLine value is defined when hardware lines are added to a digital I O object with the addline function The beginning line ID value depends on the hardware device For National Instruments hardware line IDs are zero based begin at zero Usage DIO Line Access Read write Data type Double Read only Yes when running Values are automatically defined when lines are added to the digital I O object with the addline function The default value is one Suppose you create the digital I O object dio an
165. and should be removed from your workspace using CLEAR You should remove invalid device objects from the workspace with the clear command 3 7 3 The Data Acquisition Session 3 8 Adding Channels or Lines Channels and lines are the basic hardware device elements with which you acquire or output data After you create a device object you must add channels or lines to it Channels are added to analog input and analog output objects while lines are added to digital I O objects The channels added to a device object constitute a channel group while the lines added to a device object constitute a line group The functions associated with adding channels or lines to a device object are listed below Table 3 2 Functions Associated with Adding Channels or Lines Functions Description addchannel Add hardware channels to an analog input or analog output object addline Add hardware lines to a digital I O object addmuxchannel Add channels when using a National Instruments AMUX 64T multiplexer For example to add two channels to an analog input object associated with a sound card you must supply the appropriate hardware channel identifiers IDs to addchannel ai analoginput winsound addchannel ai 1 2 Note You cannot acquire or output data with a device object that does not contain channels or lines Similarly you cannot acquire or output data with channels or lines that are not contained by a device
166. ans that data queued in the engine is ready to be output to an analog output subsystem The running state is indicated by the Running property for both analog input and analog output objects Running can be On or Off Logging or Sending For analog input objects Jogging means that data acquired from an analog input subsystem is being stored in the engine or saved to a disk file The logging state is indicated by the Logging property Logging can be On or Off For analog output objects sending means the data queued in the engine is being output to an analog output subsystem The sending state is indicated by the Sending property Sending can be On or Off Running Logging and Sending are read only properties that are automatically set to On or Off by the engine When Running is Off Logging and Sending must be Off When Running is On Logging and Sending are set to On only when a trigger occurs Note Digital I O objects also possess a running state However because they do not store data in the engine the logging and sending states do not exist Acquiring and Outputting Data Starting the Device Object You start a device object with the start function For example to start the analog input object ai ai analoginput winsound addchannel ai 1 2 start ai After start is issued the Running property is automatically set to On and both the device object and hardware device execute according to the configured and
167. are found with dagqhwinfo AlVoice analoginput winsound AIVoice analoginput nidaq 1 AIVoice analoginput mcc 1 Configuring Analog Input Triggers 2 Add channels Add one hardware channel to AIVoice chan addchannel AIVoice 1 chan addchannel AIVoice 0 For NI and MCC 3 Configure property values Define a 2 second acquisition and configure a software trigger The source of the trigger is chan and the trigger executes when a rising voltage level has a value of at least 0 2 volt duration 2 two second acquisition set AIVoice SampleRate 44100 ActualRate get AlIVoice SampleRate set AIVoice SamplesPerTrigger ActualRate duration set AIVoice TriggerChannel chan set AIVoice TriggerType Software set AIVoice TriggerCondition Rising set AIVoice TriggerConditionValue 0 2 4 Acquire data Start AlVoice acquire the specified number of samples and extract the first 1000 samples from the engine as sample time pairs Display the number of samples remaining in the engine start AIVoice data time getdata AIVoice 1000 remsamp num2str AIVoice SamplesAvailable disp Number of samples remaining in engine remsamp Plot all extracted data plot time data drawnow xlabel Time sec ylabel Signal Level Volts grid on Make sure AlVoice has stopped running before cleaning up the workspace waittilstop AIVoice 2
168. aring one reference will not invalidate the remaining references e You can restore cleared device objects to the MATLAB workspace with the daqfind function If you use the help command to display the M file help for clear then you must supply the pathname shown below help daq private clear clear Example Create the analog input object ai copy ai to a new variable aicopy and then clear the original device object from the MATLAB workspace ai analoginput winsound ch addchannel ai 1 2 aicopy ai clear ai Retrieve ai from the engine with daqfind and demonstrate that ai is identical to aicopy ainew daqfind isequal aicopy ainew ans A See Also Functions daqfind delete 10 25 daqcallback Purpose Syntax Arguments Description Remarks Example See Also 10 26 A callback function that displays event information for the specified event daqcallback obj event obj A device object event A variable that captures the event information contained by the EventLog property daqcallback obj event is an example callback function that displays information to the MATLAB command window For all events the information includes the event type and the name of the device object that caused the event to occur For events that record the absolute time in EventLog the event time is also displayed For run time error events the error message is also displayed You specify daqcallback as the ca
169. as been output from the engine These properties are given below Table 6 5 Analog Output Status Properties Property Name Description Running Indicate if the device object is running SamplesAvailable Indicate the number of samples available per channel in the engine SamplesOutput Indicate the number of samples output per channel from the engine Sending Indicate if data is being sent output to the hardware device When data is queued in the engine SamplesAvailable is updated to reflect the total number of samples per channel that was queued When start is issued Running is automatically set to On When the trigger executes Sending is automatically set to On and SamplesOutput keeps a running count of the total number of samples per channel output from the engine to the hardware Additionally 6 13 6 Analog Output SamplesAvailable tells you how many samples per channel are still queued in the engine and ready to be output to the hardware When all the queued data is output from the engine both Running and Sending are automatically set to Off SamplesAvailable is 0 and SamplesOutput reflects the total number of samples per channel that was output The Display Summary You can invoke the display summary by typing an AO object or a channel object at the MATLAB command line or by excluding the semicolon when e Creating an AO object e Adding channels e Configuring property values using the dot notation
170. as the binary vector 1 1 1 0 1 e If obj contains lines from a port configurable device then all lines will be written to even if they are not contained by the device object e An error will be returned if data is written to an input line e An error is returned if you attempt to write a negative value e If a decimal value is written to a digital I O object and the value is too large to be represented by the hardware then an error is returned Create the digital I O object dio and add four output lines to it dio digitalio nidaq 1 lines addline dio 0 3 out Write the value 8 as a decimal value and as a binary vector putvalue dio 8 putvalue dio O 0 O 1 10 85 save Purpose Syntax Arguments Description Remarks See Also 10 86 Save device objects to a MAT file save file save file obj1 obj2 file The MAT file name obj1 obj2 One or more device objects or an array of device objects save file saves all MATLAB variables to the MAT file file If an extension is not specified for file then a MAT extension is used save file obji obj2 saves the specified device objects to file Saving device objects follows these rules e You can use save in the functional form as well as the command form shown above When using the functional form you must specify the filename and device objects as strings e Samples associated with a device object are not stored in the MAT file You can bri
171. asks with your analog output hardware Output p 6 2 Managing Output Data Queue data in memory for eventual output to the hardware p 6 16 Configuring Analog Output Initiate the output of queued data to the hardware Triggers p 6 20 Events and Callbacks Enhance your analog output session using events and callbacks p 6 26 Linearly Scaling the Data Configure engineering units properties so that output data is linearly Engineering Units p 6 34 scaled Starting Multiple Device Simultaneously use your hardware s analog output and analog input Objects p 6 37 subsystems 6 Analog Output Getting Started with Analog Output 6 2 The purpose of this section is to show you how to use the Data Acquisition Toolbox to perform basic tasks with your analog output AO hardware This is accomplished by describing the most important properties and functions required for an analog output data acquisition session In addition several device specific examples are provided as well as ways to evaluate the status of the analog output object After reading this section you will be able to perform basic analog output tasks suited to your own data acquisition applications Creating an Analog Output Object You create an analog output object with the analogoutput function analogoutput accepts the adaptor name and the hardware device ID as input arguments For a list of supported adaptors refer to The Hardware Driver Adaptor on pa
172. ata you should make every effort to maximize its accuracy and precision The quality of your measurement depends on the accuracy and precision of the entire data acquisition system and can be limited by such factors as board resolution or environmental noise In general terms the accuracy of a measurement determines how close the measurement comes to the true value Therefore it indicates the correctness of the result The precision of a measurement reflects how exactly the result is determined without reference to what the result means The relative precision indicates the uncertainty in a measurement as a fraction of the result For example suppose you measure a table top with a meter stick and find its length to be 1 502 meters This number indicates that the meter stick and your eyes can resolve distances down to at least a millimeter Under most circumstances this is considered to be a fairly precise measurement with a relative precision of around 1 1500 However suppose you perform the measurement again and obtain a result of 1 510 meters After careful consideration you discover that your initial technique for reading the meter stick was faulty because you did not read it from directly above Therefore the first measurement was not accurate Making Quality Measurements Precision and accuracy are illustrated below x X x Q x x Jx x Not precise Precise Not accurate Not accurate KN x Not precise Precise
173. ata becomes a blocking function until there is enough space in the queue to add the additional data Characteristics Usage AO Common Access Read only Data type Double Read only N A when running Values The value is calculated by the data acquisition engine See Also Functions daqmem putdata 11 51 Name Purpose Description Characteristics Values Example 11 52 Specify a descriptive name for the device object When a device object is created a descriptive name is automatically generated and stored in Name This name is produced by concatenating the name of the adaptor the device ID and the device object type You can change the value of Name at any time Usage AI AO DIO Common Access Read write Data type String Read only No when running The value is defined after the device object is created Create the analog input object ai for a sound card ai analoginput winsound The descriptive name for ai is given by ai Name ans winsoundO AI NativeOffset Purpose Description Characteristics Values Example Indicate the offset to use when converting between the native data format and doubles NativeOffset along with NativeScaling is used to convert data between the native hardware format and doubles For analog input objects you return native data from the engine with the getdata function Additionally if you log native data to a daq file then you can read back tha
174. ata to be queued in the engine follows these rules e Data is output as soon as a trigger occurs e An error is returned if a NaN is included in the data stream 6 Analog Output 6 18 e You can use the native data type of the hardware Note that MATLAB supports math operations only for the double data type Therefore to use math functions on native data you must convert it to doubles e If the data is not within the range of the UnitsRange property then it is clipped to the maximum or minimum value specified by UnitsRange Refer to Linearly Scaling the Data Engineering Units on page 6 34 for more information about clipping Example Queuing Data with putdata This example illustrates how you can use putdata to queue 8000 samples and then output the data a total of five times using the RepeatOutput property You can run this example by typing daqdoc6_3 at the MATLAB command line 1 Create a device object Create the analog output object AO for a sound card The installed adaptors and hardware IDs are found with daqhwinfo AO analogoutput winsound A0 analogoutput nidaq 1 A0 analogoutput mcc 1 2 Add channels Add one channel to AO chans addchannel A0O 1 chans addchannel A0 0 For NI and MCC 3 Configure property values Define an output time of one second assign values to the basic setup properties generate data to be queued and issue two putdata calls Because the queued
175. atch the names of the loaded device objects If no device objects are specified then all variables existing in the MAT file are loaded Loading device objects follows these rules Unique device objects are loaded into the MATLAB workspace as well as the engine e If a loaded device object already exists in the engine but not the MATLAB workspace the loaded device object automatically reconnects to the engine device object e Ifa loaded device object already exists in the workspace or the engine but has different properties than the loaded object then these rules are followed The read only properties are automatically reset to their default values All other property values are given by the loaded object and a warning is issued stating that property values of the workspace object have been updated 10 71 load Example See Also 10 72 e If the workspace device object is running then it is stopped before loading occurs e If identical device objects are loaded then they point to the same device object in the engine For example if you saved the array x ail ail ai2 only ail and ai2 are created in the engine and x 1 will equal x 2 e Values for read only properties are restored to their default values upon loading For example the EventLog property is restored to an empty vector Use the propinfo function to determine if a property is read only e Values for the Buf feringConf ig property when the Buffe
176. ate the absolute time of the first trigger Time TriggerFen Specify the M file callback function to execute when a trigger occurs Properties By Category Analog Output Trigger Properties Continued TriggersExecuted Indicate the number of triggers that execute TriggerType Specify the type of trigger to execute Analog Output Status Properties Running Indicate if the device object is running SamplesAvailable Indicate the number of samples available per channel in the engine SamplesOutput Indicate the number of samples output per channel from the engine Sending Indicate if data is being sent to the hardware device Analog Output Hardware Configuration Properties ClockSource Specify the clock used to govern the hardware conversion rate SampleRate Specify the per channel rate at which digital data is converted to analog data Analog Output Data Management Properties MaxSamplesQueued Indicate the maximum number of samples that can be queued in the engine 11 bs Property Referenc Analog Output Data Management Properties Continued RepeatOutput Timeout Specify the number of additional times queued data is output Specify an additional waiting time to queue data Analog Output Callback Properties RuntimeErrorFen SamplesOutputFecn SamplesOutput FenCount StartFen StopFcn TimerFen TimerPeriod TriggerFecn Specify the
177. ate the analog input object ai for a sound card and add two channels to it ai analoginput winsound addchannel ai 1 2 Assign ai a label using Tag set ai Tag Sound If ai is cleared from the workspace you can use daqfind and the Tag value to identify and retrieve the device object clear ai aicell daqfind Tag Sound ai aicell 1 Functions daqfind 11 79 Timeout Purpose Description Characteristics Values See Also 11 80 Specify an additional waiting time to extract or queue data The Timeout value in seconds is added to the time required to extract data from the engine or queue data to the engine Because data is extracted with the getdata function and queued with the putdata function Timeout is associated only with these two blocking functions If the requested data is not extracted or queued after waiting the required time then a timeout condition occurs and control is immediately returned to MATLAB A timeout is one of the conditions for stopping an acquisition When a timeout occurs the callback function specified by RuntimeErrorFcn is called Timeout is not associated with hardware timeout conditions Possible hardware timeout conditions include e Triggering on a voltage level and that level never occurs e Externally clocking an acquisition and the external clock signal never occurs e Losing the hardware connection To check for hardware timeouts you might need to
178. ated as data is acquired For analog output objects the default number of blocks is zero Create the analog input object ai for a sound card and add two channels to it ai analoginput winsound addchannel ai 1 2 The block size and number of blocks are given by BufferingConfig while the native data type for the sound card is given by daqhwinfo ai BufferingConfig ans 512 30 out daqhwinfo ai out NativeDataType ans int16 With this information the total allocated memory is calculated to be 61 440 bytes This number is stored by daqmem out daqmem ai out UsedBytes ans 61440 The allocated memory is more than sufficient to store 8000 two byte samples for two channels If more memory was required then the number of blocks would dynamically grow because BufferingMode is set to Auto Functions daqhwinfo daqmem Properties BufferingMode SampleRate SamplesPerTrigger BufferingMode Purpose Description Characteristics Values See Also Specify how memory is allocated BufferingMode can be set to Auto or Manual If Buf feringMode is set to Auto the data acquisition engine automatically allocates the required memory If Buf feringMode is set to Manual you must manually allocate memory with the BufferingConfig property If Buf feringMode is set to Auto and the SampleRate value is changed then the BufferingConfig values might be recalculated by the engine Specifically you can increase
179. ation and the frequency components of the device while it is vibrating The accelerometer has a range of 50 g s a voltage sensitivity of 99 7 mV g and a resolution of 0 00016 g linearly Scaling the Data Engineering Units The accelerometer signal is input to a Tektronix TDS 210 digital oscilloscope and to channel 0 of the data acquisition board By observing the signal on the scope the maximum expected range of data from the sensor is 200 mV which corresponds to approximately 2 gs Given this constraint you should configure the board s input range to 500 mV which is the closest input range that encompasses the expected data range You can run this example by typing daqdoc5_8 at the MATLAB command line 1 Create a device object Create the analog input object AI for a National Instruments board The installed adaptors and hardware IDs are found with daqhwinfo AI analoginput nidagq 1 2 Add channels Add one hardware channel to AI chan addchannel AI 0 3 Configure property values Configure the sampling rate to 200 kHz and define a two second acquisition duration 2 ActualRate setverify AI SampleRate 200000 set AI SamplesPerTrigger duration ActualRate Configure the engineering units properties This example assumes you are using a National Instruments PCI 6024E board or an equivalent hardware device SensorRange is set to the maximum accelerometer range in volts and UnitsRange is
180. ay data is measured Properties By Category Analog Input Trigger Properties Continued TriggerRepeat TriggersExecuted TriggerType Specify the number of additional times the trigger executes Indicate the number of triggers that execute Specify the type of trigger to execute Analog Input Status Properties Logging Running SamplesAcquired SamplesAvailable Indicate if data is being logged to memory or to a disk file Indicate if the device object is running Indicate the number of samples acquired per channel Indicate the number of samples available per channel in the engine Analog Input Hardware Configuration Properties ChannelSkew ChannelSkewMode ClockSource InputType SampleRate Specify the time between consecutive scanned hardware channels Specify how the channel skew is determined Specify the clock used to govern the hardware conversion rate Specify the analog input hardware channel configuration Specify the per channel rate at which analog data is converted to digital data 11 bs Property Referenc Analog Input Callback Properties DataMissedFcn InputOverRange Fen RuntimeErrorFen SamplesAcquired Fen SamplesAcquired FenCount StartFen StopFcn TimerFen TimerPeriod TriggerFecn Specify the M file callback function to execute when data is missed Specify the M file callback function to execute
181. bout a specific function refer to Chapter 10 Function Reference If you want detailed information about a specific property refer to Chapter 11 Base Property Reference or Chapter 12 Device Specific Property Reference Using This Guide Using the Documentation Examples When you encounter examples or code snippets in this book you might want to try them for yourself An easy way to do this is to cut the relevant text from the PDF or HTML versions of this guide and paste it into the MATLAB workspace You access the PDF and HTML content with the Help browser Some examples are constructed as mini applications that illustrate one or two important toolbox features and serve as templates so you can see how to build applications that suit your specific needs These examples are included as toolbox M files and are treated as demos You can list all Data Acquisition Toolbox demos by typing help daqdemos All documentation example M files begin with daqdoc To run an example type the M file name at the command line Note that most examples are written for specific hardware devices To use these examples with your hardware device you should modify the creation function input arguments and the device object property values as needed How This Guide Is Organized The organization of this guide is described below Chapter Description Introduction to Data Provides you with general information about Acquisition makin
182. can easily configure or return property values for one or more channels As described in Referencing Individual Hardware Channels on page 4 5 you can also access channels with the Channel property Once you add channels to an analog output object the properties listed below are automatically assigned values These properties provide descriptive information about the channels based on their class type and ID Table 6 2 Descriptive Analog Output Channel Properties Property Name Description HwChannel Specify the hardware channel ID Index Indicate the MATLAB index of a hardware channel Parent Indicate the parent device object of a channel Type Indicate a channel You can display the values of these properties for chans with the get function get chans HwChannel Index Parent Type ans 0 1 1x1 analogoutput Channel 1 2 1x1 analogoutput Channel To reference individual channels you must specify either MATLAB indices or descriptive channel names Refer to Referencing Individual Hardware Channels on page 4 5 for more information Getting Started with Analog Output Configuring Analog Output Properties After hardware channels are added to the analog output object you should configure property values As described in Configuring and Returning Properties on page 3 12 the Data Acquisition Toolbox supports two basic types of properties for analog output objects common prope
183. ccurred up to the time of the getdata call data getdata obj extracts the number of samples specified by the SamplesPerTrigger property for each channel contained by obj data is an m by n array where m is the number of samples extracted and n is the number of channels data getdata obj samples extracts the number of samples specified by samples for each channel contained by obj 10 59 getdata Remarks 10 60 data getdata obj type extracts data in the specified format If type is specified as native the data is returned in the native data format of the device If type is specified as double the default the data is returned as doubles data getdata obj samples type extracts the number of samples specified by samples in the format specified by type for each channel contained by obj data time getdata returns data as sample time pairs time is an m by 1 array of relative time values where m is the number of samples returned Relative time is measured with respect to the first sample logged by the engine data time abstime getdata extracts data as sample time pairs and returns the absolute time of the trigger The absolute time is returned as a clock vector and is identical to the value stored by the InitialTriggerTime property data time abstime events getdata extracts data as sample time pairs returns the absolute time of the trigger and returns a structure containing a list of
184. cept for TriggerFcn these trigger related properties are discussed in the following sections TriggerFcn is discussed in Events and Callbacks on page 6 26 Configuring Analog Output Triggers Defining a Trigger Trigger Types Defining a trigger for an analog output object involves specifying the trigger type with the TriggerType property You can think of the trigger type as the source of the trigger The analog output TriggerType values are given below Table 6 8 Analog Output TriggerType Property Values TriggerType Value Description Immediate The trigger occurs just after you issue the start function Manual The trigger occurs just after you manually issue the trigger function Trigger types can be grouped into two main categories e Device independent triggers e Device specific hardware triggers The trigger types shown above are device independent triggers because they are available for all supported hardware For these trigger types the callback that initiates the trigger event involves issuing a toolbox function start or trigger Conversely device specific hardware triggers depend on the specific hardware device you are using For these trigger types the callback that initiates the trigger event involves an external digital signal Device specific hardware triggers for National Instruments and Agilent Technologies devices are discussed in Device Specific Hardware Triggers on page 6 24 Device
185. ces when configuring channel property values For scanning hardware the scan order follows the MATLAB index Therefore the hardware channel associated with index 1 is sampled first the hardware channel associated with index 2 is sampled second and so on To change the scan order you can specify a permutation of the indices with Channel Usage AI AO Common Access Read write Data type Vector of channels Read only Yes when running Values are automatically defined when channels are added to the device object with the addchannel function The default value is an empty column vector Create the analog input object ai for a National Instruments card and add three hardware channels to it ai analoginput nidaq 1 addchannel ai 0 2 To set a property value for the first channel added ID 0 you must reference the channel by its index using the Channel property chans ai Channel 1 set chans InputRange 10 10 Channel Based on the current configuration the hardware channels are scanned in order from 0 to 2 To swap the scan order of channels 0 and 1 you can specify the appropriate permutation of the MATLAB indices with Channel ai Channel 1 2 3 ai Channel 2 1 3 See Also Functions addchannel delete Properties HwChannel Index 11 19 ChannelName Purpose Description Characteristics Values Example See Also 11 20 Specify a descriptive channel name ChannelName spec
186. change the scan order you can assign the channel IDs to different indices using the HwChannel or Channel property Index provides a convenient way to access channels and lines programmatically Usage AI AO Channel DIO Line Access Read only Data type Double Read only N A when running Values are automatically defined when channels lines are added to the device object with the addchannel addline function The default value is one Index Example Create the analog input object ai for a sound card and add two hardware channels to it ai analoginput winsound chans addchannel ai 1 2 You can access the MATLAB indices for these channels with Index Indexi chans 1 Index Index2 chans 2 Index See Also Functions addchannel addline Properties Channel HwChannel HwLine Line 11 35 InitialTriggerTime Purpose Description Characteristics Values Example 11 36 Indicate the absolute time of the first trigger For all trigger types InitialTriggerTime records the time when Logging or Sending is set to On The absolute time is recorded as a clock vector You can return the InitialTriggerTime value with the getdata function or with the Data AbsTime field of the EventLog property Usage AI AO Common Access Read only Data type Six element vector of doubles Read only N A when running The value is automatically updated when the trigger executes The default value is a vect
187. channel provided channel 1 is added first addchannel ai 1 addchannel ai 2 Alternatively you can use one call to addchannel provided channel 1 is specified as the first element of the hardware ID vector addchannel ai 1 2 Stereo mode means that data is acquired from both hardware channels Channel 1 is automatically assigned the descriptive name Left and channel 2 is automatically assigned the descriptive name Right ai Channel ChannelName ans Left Right While in stereo mode if you want to delete one channel then that channel must be channel 2 If you try to delete channel 1 an error is returned delete ai Channel 2 The sound card is now in mono mode 4 7 4 Getting Started with Analog Input 4 8 Configuring Analog Input Properties After hardware channels are added to the analog input object you should configure property values As described in Configuring and Returning Properties on page 3 12 the Data Acquisition Toolbox supports two basic types of properties for analog input objects common properties and channel properties Common properties apply to all channels contained by the device object while channel properties apply to individual channels The properties you configure depend on your particular analog input application For many common applications there is a small group of properties related to the basic setup that you will typically use These basic setup properties contro
188. check for valid channels use the isvalid function Typically you use ischannel directly only when you are creating your own M files Suppose you create the function myfunc for use with the Data Acquisition Toolbox If myfunc is passed one or more channels as an input argument then the first thing you should do in the function is check if the argument is a channel function myfunc chan Determine if a channel was passed if ischannel chan error The argument passed is not a channel end You can examine the Data Acquisition Toolbox M files for examples that use ischannel Functions isvalid 10 65 isdioline Purpose Syntax Arguments Description Remarks Example See Also 10 66 Check for lines out isdioline obj Line index obj Line index One or more lines contained by obj out A logical value out isdioline obj Line index returns a logical 1 to out if obj Line index is a line Otherwise a logical 0 is returned isdioline does not determine if lines are valid associated with hardware To check for valid lines use the isvalid function Typically you use isdioline directly only when you are creating your own M files Suppose you create the function myfunc for use with the Data Acquisition Toolbox If myfunc is passed one or more lines as an input argument then the first thing you should do in the function is check if the argument is a line function myfunc line Determin
189. cified range of values Entering The trigger occurs when the signal enters the specified range of values 11 85 TriggerCondition Agilent Technologies The following trigger conditions are available when TriggerType is HwDigital PositiveEdge The trigger occurs when the positive rising edge of a digital signal is detected NegativeEdge The trigger occurs when the negative falling edge of a digital signal is detected The following trigger conditions are available when TriggerType is HwAnalog Rising The trigger occurs when the analog signal has a positive slope when passing through the specified range of values Falling The trigger occurs when the analog signal has a negative slope when passing through the specified range of values Leaving The trigger occurs when the analog signal leaves the specified range of values Entering The trigger occurs when the analog signal enters the specified range of values Note that when TriggerType is HwAnalog the trigger condition values are all specified as two element vectors Setting two trigger levels prevents the module from triggering repeatedly because of a noisy signal 11 86 TriggerCondition Keithley The following trigger conditions are available when TriggerType is HwDigital PositiveEdge NegativeEdge GateHigh GateLow The trigger occurs when the positive rising edge of the digital signal is detected The trigger occurs when the ne
190. cify you should return the actual input range for each channel using the get function or the device object display summary Alternatively you can use the setverify function which sets the InputRange value and then returns the actual value that is set Note If your hardware supports a channel gain list then you can configure InputRange for individual channels Otherwise InputRange must have the same value for all channels contained by the analog input object You should use InputRange in conjunction with the SensorRange property These two properties should be configured such that the maximum precision is obtained and the full dynamic range of the sensor signal is covered 11 39 InputRange Characteristics Values Example See Also 11 40 Usage AI Channel Access Read write Data type Two element vector of doubles Read only Yes when running The default value is supplied by the hardware driver Create the analog input object ai for a National Instruments board and add two hardware channels to it ai analoginput nidaq 1 addchannel ai 0 1 You can return the input ranges supported by the board with the InputRanges field of the daqhwinfo function out daqhwinfo ai out InputRanges ans 0 0500 0 0500 0 5000 0 5000 5 0000 5 0000 10 0000 10 0000 To configure both channels contained by ai to accept input signals between 10 volts and 10 volts ai Channel InputRange 10 10 Alterna
191. ck function as the value for an callback property then the function is executed when the event associated with the callback property occurs A property associated with a specific event type When an event occurs the engine examines the associated callback property If a callback function is given as the value for the callback property then that function is executed All event types have a callback property A component of an analog input subsystem or an analog output subsystem that you read data from or write data to The collection of channels contained by an analog input object or an analog output object For scanning hardware the channel group defines the scan order Channel property Channel skew Common property Configuration Counter timer subsystem D A converter Data acquisition session Data block Device object Device specific property Differential input Digital O subsystem DMA A property that applies to individual channels The time gap between consecutively sampled channels Channel skew exists only for scanning hardware A property that applies to every channel or line contained by a device object The process of supplying the device object with the resources and information necessary to carry out the desired tasks Configuration consists of two steps adding channels or lines and setting property values to establish the desired behavior Hardware that is used for event counting
192. cquisition Toolbox demos for analey input objects Intreduction illustrates a basic data acquisition session using an analog input object Channels intreduces adding and configuring analey input channels Triggers illustrates how data can be acquired using an immediate manual and software trigger Data Legging illustrates how to configure an analog input object for data legging Introduction Channels Triggers Data Logging All demos have an associated M file which are listed below To run a particular demo type the M file name at the command line Common Demos The common demos illustrate features that are common to all supported device objects These demos are listed below Demo Name Description demodaq_callback demodaq_intro demodaq_save daqtimerplot Introduction to callback functions Introduction to the Data Acquisition Toolbox Save and load device objects Example callback function that plots acquired data Understanding the Toolbox Capabilities Analog Input Demos The analog input demos are listed below Demo Name Description daqrecord daqscope demoai_channel demoai_fft demoai_intro demoai_logging demoai_trig Record data from the specified adaptor Example oscilloscope Introduction to analog input channels Fast Fourier transform FFT of an incoming signal Introduction to analog input objects Demonstrate logging data to a disk file Demonstrat
193. cription AbsTime The absolute time as a clock vector the event occurred RelSample The acquired AI or output AO sample number when the event occurred Channel The index number for each input channel serving as a trigger source AI only Trigger The trigger number AI only Usage AI AO Common Access Read write Data type String Read only No when running The default value is an empty string Functions trigger Properties EventLog Logging 11 83 TriggerChannel Purpose Description Characteristics Values Example See Also 11 84 Specify the channel serving as the trigger source TriggerChannel specifies the channel serving as the trigger source The trigger channel must be specified before the trigger type You might need to configure the TriggerCondition and TriggerConditionValue properties in conjunction with TriggerChannel For all supported vendors if TriggerType is Software then you must acquire data from the channel being used for the trigger source For National Instruments hardware if TriggerType is HwAnalogChannel then TriggerChannel must be the first element of the channel group The exception is if you are using the PCI 6110 or PCI 6111 board In this case you can specify any channel for the TriggerChannel value Usage AI Common Access Read write Data type Vector of channels Read only Yes when running The default value is an empty vector Create the analog
194. ct for continuous acquisition by use an immediate trigger and setting SamplesPerTrigger or TriggerRepeat to inf Trigger repeats are discussed in Repeating Triggers on page 5 29 Manual Trigger If TriggerType is Manual the trigger occurs just after you issue the trigger function A manual trigger might provide you with more control over the data that is logged For example if the acquired data is noisy you can preview the data using peekdata and then manually execute the trigger after you observe that the signal is well behaved Software Trigger If TriggerType is Software the trigger occurs when a signal satisfying the specified condition is detected on the hardware channel specified by the TriggerChannel property The trigger condition is specified as either a voltage value and slope or a range of voltage values using the TriggerCondition and TriggerConditionValue properties Example Voice Activation Using a Software Trigger This example demonstrates how to configure an acquisition with a sound card based on voice activation The sample rate is set to 44 1 kHz and data is logged when an acquired sample has a value greater than or equal to 0 2 volt anda rising slope A portion of the data is then extracted from the engine and plotted You can run this example by typing daqdoc5_3 at the MATLAB command line 1 Create a device object Create the analog input object AlVoice for a sound card The installed adaptors and hardware IDs
195. ction e If you delete a device object while it is running then a warning is issued before it is deleted You cannot delete a device object while it is logging or sending data You should use delete at the end of a data acquisition session You can quickly delete all existing device objects with the command delete daqfind 10 49 delete Example See Also 10 50 If you use the help command to display the M file help for delete then you must supply the pathname shown below help daq daqdevice delete National Instruments Create the analog input object ai for a National Instruments board add hardware channels 0 7 to it and make a copy of hardware channels 0 and 1 ai analoginput nidaq 1 addchannel ai 0 7 ch ai Channel 1 2 To delete hardware channels 0 and 1 delete ch These channels are deleted from the data acquisition engine and are no longer associated with ai The remaining channels are reindexed such that the indices begin at 1 and increase monotonically to 6 To delete ai delete ai Sound Card Create the analog input object AI1 for a sound card and configure it to operate in stereo mode AI1 analoginput winsound addchannel AI1 1 2 You can now configure the sound card for mono mode by deleting hardware channel 2 delete AI1 Channel 2 If hardware channel 1 is deleted instead an error is returned Functions clear daqreset digitalio Purpose Syntax Arg
196. ction or property specified by name The help text is returned to out out daqhelp obj returns a complete listing of functions and properties for the device object obj to out Help for obj s constructor is also displayed out daghelp obj name returns help for name for the specified device object obj to out name can be a constructor adaptor property or function name 10 29 daghelp Remarks 10 30 As shown below you can also display help via the Workspace browser by right clicking a device object and selecting Explore gt DAQ Help from the context menu inixi Fie Edit View Web Window Help o gt A sejf z e ai iel 1332 analoginput object 1x3 24 doub Open E parpo 1x1 1308 dict MB Display Summary Call Property Editor Select All ne Ready i Display Hardware Info Access context pop up menus a E Show DAQ Events by right clicking a device object Save Selection As Save Workspace As DAQ Help Copy Delete Clear Workspace Rename More About Displaying Help e When displaying property help the names in the See Also section that contain all uppercase letters are function names The names that contain a mixture of upper and lowercase letters are property names e When displaying function help the See Also section contains only function names Rules for Specifying Names For the daqhelp name syntax e If name is the name of a constructor a co
197. curs before the first trigger executes The String Field String is used by the run time error event to store the descriptive message that is generated when a run time error occurs This message is also displayed at the MATLAB command line The Trigger Field Trigger is used by the trigger event to indicate the trigger number For example if three trigger events occur then Trigger is 3 for the third trigger event The total number of triggers executed is given by the TriggersExecuted property 5 49 5 Doing More with Analog Input 5 50 Example Retrieving Event Information Suppose you want to examine the events logged for the example given by Example Voice Activation Using a Software Trigger on page 5 22 You can do this by accessing the EventLog property events AIVoice EventLog events 3x1 struct array with fields Type Data By examining the contents of the Type field you can list the events that occurred while AIVoice was running events Type ans Start Trigger Stop To display information about the trigger event you must access the Data field which stores the absolute time the trigger occurred the number of samples acquired when the trigger occurred the index of the trigger channel and the trigger number trigdata events 2 Data trigdata AbsTime 1999 4 15 18 12 5 8615 RelSample 0 Channel 1 Trigger 1 You can display a summary of the event log with the showdaqevents functio
198. d display its state Refer to the diopanel demo for an example of this behavior If you want to synchronize the input and output of data or you require more control over when your hardware starts you should use the ManualTriggerHwOn property Functions stop trigger Properties EventLog ManualTriggerHwOn Running Sending TriggerType stop Purpose Syntax Arguments Description Remarks Stop a device object stop obj obj A device object or an array of device objects stop obj terminates the execution of the device object obj An analog input object automatically stops when the requested samples are acquired or data is missed An analog output object automatically stops when the queued data is output These two device objects can also stop executing under one of these conditions e The Timeout property value is reached e A run time error occurs For analog input objects stop must be used when the TriggerRepeat property or SamplesPerTrigger property is set to inf For analog output objects stop must be used when the RepeatOutput property is set to inf When stop is issued for either of these device objects e The Running property is set to Off e The Logging property or Sending property is set to Off e The M file callback function specified for StopFcn is executed e The stop event is recorded in the EventLog property For any device object you can specify stop as the value for a callback property a
199. d add four hardware lines to it dio digitalio nidaq 1 addline dio 0 3 out addline automatically assigns the indices 1 4 to these hardware lines You can swap the hardware lines associated with index 1 and index 2 with HwLine dio Line 1 HwLine 1 dio Line 2 HwLine 0 Functions addline Properties Line Index 11 33 Index Purpose Description Characteristics Values 11 34 Indicate the MATLAB index of a hardware channel or line Every hardware channel line contained by a device object has an associated MATLAB index that is used to reference that channel line For example to configure property values for an individual channel you must reference the channel through the Channel property using the appropriate Index value Likewise to configure property values for an individual line you must reference the line through the Line property using the appropriate Index value For channels lines you can assign indices automatically with the addchannel addline function Channel line indices always begin at 1 and increase monotonically up to the number of channels lines contained by the device object For channels index assignments can also be made manually with the addchannel function For scanning hardware the scan order follows the MATLAB index Therefore the hardware channel associated with index 1 is sampled first the hardware channel associated with index 2 is sampled second and so on To
200. d as an M file into the MATLAB workspace type the name of the M file at the command line For example to load ai from the M file myai m ai myai Note that the read only properties such as SamplesAcquired and SamplesAvailable are restored to their default values get ai SamplesAcquired SamplesAvailable ans 0 0 When loading ai into the workspace the MAT file myai mat is automatically loaded and the TriggerFcn property value is restored ai TriggerFcn ans mycallback 7 3071e 005 8 3 8 Saving and Loading the Session 8 4 Saving Device Objects to a MAT File You can save a device object to a MAT file just as you would any workspace variable using the save command For example to save the analog input object ai and the variable time defined in the preceding section to the MAT file myail mat save myai1 ai time Read only property values are not saved Therefore read only properties use their default values when you load the device object into the MATLAB workspace To determine if a property is read only use the propinfo function or examine the property reference pages Loading the Device Object To load a device object that was saved to a MAT file into the MATLAB workspace use the load command For example to load ai and time from MAT file myaii mat load myait Logging Information to Disk Logging Information to Disk While an analog input object is running you can log this infor
201. d data from the engine and plot the data data getdata AI subplot 212 plot data grid on title All Acquired Data xlabel Samples ylabel Signal level volts 5 15 5 Doing More with Analog Input 5 Clean up When you no longer need AI you should remove it from memory and from the MATLAB workspace delete AI clear AI The data is shown below Preview Data io gt ze S gt lt 0 o gt o pa 30 1 E 2 0 2 0 3 i 100 200 300 400 500 600 700 800 Samples All Acquired Data 0 3 T T Signal level volts Samples 5 16 Managing Acquired Data Returning Time Information You can return relative time and absolute time information with the getdata function Relative time is associated with the extracted data Absolute time is associated with the first trigger executed Relative Time To return data and relative time information for the analog input object ai data time getdata ai time is an m by 1 array of relative time values where m is the number of samples returned time 0 corresponds to the first sample logged by the data acquisition engine and time is measured continuously until the acquisition is stopped The relationship between the samples acquired and the relative time for each sample is shown below for m samples and n channels Data array Each column Relative time array represents one channel dii di
202. d to obj depends on the number of mux boards used For example suppose you are using a data acquisition board with 16 channels connected to one mux board If chanid is 0 then addmuxchannel adds four channels Refer to the AMUX 64T User Manual for more information about adding mux channels based on hardware channel IDs and the number of mux boards used chans addmuxchannel returns the channels added to chans Before using addmuxchannel you must set the NumMuxBoards property to the appropriate value You can use as many as four mux boards with one analog input object addmuxchannel deletes all channels contained by obj before new channels are added Functions muxchanidx analoginput Purpose Syntax Arguments Description Remarks Create an analog input object AI analoginput adaptor AI analoginput adaptor ID adaptor The hardware driver adaptor name The supported adaptors are hpe1432 keithley mcc nidaq parallel and winsound ID The hardware device identifier ID is optional if the device object is associated with a sound card having an ID of 0 AI The analog input object AI analoginput adaptor creates the analog input object AI for a sound card having an ID of 0 adaptor must be winsound This is the only case where ID is not required AI analoginput adaptor ID creates the analog input object AI for the specified adaptor and for the hardware device with device identifier ID
203. data sample The flow of output data consists of these two independent steps 1 Data from MATLAB is queued in the engine 2 Data queued in the engine is output to the hardware These two steps are illustrated below MATLAB 1 Queue data into the engine Data Acquisition Toolbox Data acquisition engine Queued data 2 Output data to the hardware Hardware gt Actuators Toolbox Components The Hardware Driver Adaptor The hardware driver adaptor or just adaptor is the interface between the data acquisition engine and the hardware driver The adaptor s main purpose is to pass information between MATLAB and your hardware device via its driver Hardware drivers are provided by your device vendor For example to acquire data using a National Instruments board the appropriate version of the NI DAQ driver must be installed on your platform Hardware drivers are not installed as part of the Data Acquisition Toolbox with the exception of a special parallel port driver that allows access to the port s protected memory addresses Additionally a suitable driver is usually installed on PCs that are equipped with a sound card For the remaining supported devices the drivers must be installed The vendors device types and the associated adaptor names used by the toolbox are listed below Table 2 1 Support
204. dd to a device object You can return the channel IDs with the daqhwinfo function For example suppose you create the analog input object ai for a National Instruments board To display the differential channel IDs ai analoginput nidaq 1 hwinfo daghwinfo ai hwinfo DifferentialIDs ans 0 1 2 3 4 5 6 7 In contrast the single ended channel IDs would be numbered 0 through 15 Note Ifthe InputType value is changed and that change decreases the number of channels contained by the analog input object then a warning is returned and all channels are deleted 5 3 5 Doing More with Analog Input 5 4 Agilent Technologies Devices For Agilent Technologies devices the only valid InputType value is Differential Channels configured for differential input are not connected to a fixed reference such as earth and the input signals are measured as the difference between two terminals Keithley and Measurement Computing Devices For Keithley and Measurement Computing devices InputType can be Differential or SingleEnded Channels configured for differential input are not connected to a fixed reference such as earth and the input signals are measured as the difference between two terminals Channels configured for single ended input are connected to a common ground and input signals are measured with respect to this ground National Instruments Devices For National Instruments devices InputType can be Differential S
205. ddchannel obj hwch names chans addchannel obj hwch index names Arguments obj An analog input or analog output object hwch Specifies the numeric IDs of the hardware channels added to the device object Any MATLAB vector syntax can be used index The MATLAB indices to associate with the hardware channels Any MATLAB vector syntax can be used provided the vector elements are monotonically increasing names A descriptive channel name or cell array of descriptive channel names chans A column vector of channels with the same length as hwch Description chans addchannel obj hwch adds the hardware channels specified by hwch to the device object obj The MATLAB indices associated with the added channels are assigned automatically chans is a column vector of channels chans addchannel obj hwch index adds the hardware channels specified by hwch to the device object obj index specifies the MATLAB indices to associate with the added channels chans addchannel obj hwch names adds the hardware channels specified by hwch to the device object obj The MATLAB indices associated with the added channels are assigned automatically names is a descriptive channel name or cell array of descriptive channel names chans addchannel obj hwch index names adds the hardware channels specified by hwch to the device object obj index specifies the MATLAB indices to associate with the added channels names is a descriptive cha
206. dding channels 4 3 creating 4 2 display summary 4 22 engineering units 5 55 events and callbacks 5 45 extracting data 5 12 logging data 4 13 information to disk 8 5 previewing data 5 8 properties basic setup 4 8 channel 11 7 common 11 3 configuring 3 18 sampling rate 4 8 starting 4 12 status evaluation 4 21 stopping 4 13 triggers configuring 5 19 types 4 10 I 1 Index IT 2 analog output object adding channels 6 3 creating 6 2 display summary 6 14 engineering units 6 34 events and callbacks 6 26 output continuous 6 21 single point 10 84 properties basic setup 6 5 channel 11 11 common 11 8 configuring 3 18 queueing data for output 6 8 sampling rate 6 5 starting 6 8 status evaluation 6 13 stopping 6 9 triggers configuring 6 20 types 6 7 analog triggers Agilent hardware 5 38 MCC hardware 5 41 NI hardware 5 43 analoginput function 10 17 analogoutput function 10 20 antialiasing filter 1 33 array data returned by getdata 5 12 device object 3 5 B bandwidth 1 10 base properties 3 13 BiDirectionalBit property 12 8 binary vector 7 12 binvec2dec function 10 23 BitsPerSample property 12 9 block See data block blocking function getdata 5 12 putdata 6 8 board ID 4 2 buffer configuration 11 15 extracting data 5 13 previewing data 5 9 queuing data 6 16 BufferingConfig property 11 15 BufferingMode property 11 17 C calibration 1 2 callback function 5 51 callback properties AI object 5 45 AO object
207. de the maximum and minimum sampling rates the channel gains the hardware channel or line IDs and the vendor driver version daqhwinfo Remarks Example out daqhwinfo obj FieldName returns the hardware related information specified by FieldName for the device object obj FieldName can be a single field name or a cell array of field names out is an m by n cell array where m is the length of obj and n is the length of FieldName You can return a list of valid field names with the daqhwinfo obj syntax As shown below you can also return hardware information via the Workspace browser by right clicking a device object and selecting Explore gt Display Hardware Info from the context menu inixi File Edit View Web Window Help pe A BF Stade Base 7 lxl 1332 analoginput object Display Summary Call Property Editor parpor 1x1 1308 digit Select All Access context pop up menus by right clicking a device object Ready Display Hardware Info BT Show DAQ Events Import Data Save Selection As Save Workspace As DAQ Help Copy Delete Clear Workspace Rename Display all installed adaptors Note that this list might be different for your platform out dagqhwinfo out InstalledAdaptors ans keithley mcc nidaq parallel winsound 10 33 daqhwinfo 10 34 To display the device object constructor names for all installed winsound devices
208. default property values While you are acquiring data with an analog input object you can preview the data with the peekdata function peekdata takes a snapshot of the most recent data but does not remove data from the engine For example to preview the most recent 500 samples acquired by each channel contained by ai data peekdata ai 500 Because previewing data is usually a low priority task peekdata does not guarantee that all requested data is returned You can preview data at any time while the device object is running Logging or Sending Data While the device object is running you can e Log data acquired from an analog input subsystem to the engine memory or to a disk file e Output data queued in the engine to an analog output subsystem However before you can log or send data a trigger must occur You configure an analog input or analog output trigger with the TriggerType property All the examples presented in this section use the default TriggerType value of Immediate which executes the trigger immediately after the start function is issued For a detailed description of triggers refer to Configuring Analog Input Triggers on page 5 19 or Configuring Analog Output Triggers on page 6 20 3 23 3 The Data Acquisition Session 3 24 Extracting Logged Data When a trigger occurs for an analog input object the Logging property is automatically set to On and data acquired from the hardware is log
209. device ID For sound cards the device identifier is typically not exposed to you through the Microsoft Windows environment However the Data Acquisition Toolbox automatically associates each sound card with an integer ID value There are two cases to consider e If you have one sound card installed then ID is 0 You are not required to specify ID when creating an analog input object associated with this device e If you have multiple sound cards installed the first one installed has an ID of 0 the second one installed has an ID of 1 and so on You must specify ID when creating analog input objects associated with devices not having an ID of 0 There are two ways you can determine the ID for a particular device e Type daqhwinfo adaptor e Execute the vendor supplied device configuration utility National Instruments To create an analog input object for a National Instruments board defined as device number 1 AI analoginput nidaq 1 Agilent Technologies To create an analog input object for an Agilent Technologies module with device identifier 1 residing in VXI chassis 0 AI analoginput hpe1432 vxi0 1 instr Alternatively you can use the syntax AI analoginput hpe1432 1 0 analoginput The HP driver allows you to span multiple hardware devices To create an analog input object that spans two HP devices with device identifiers 1 and 2 residing in VXI chassis 0 AI analoginput hpe1432 vxi
210. digital lines with the putvalue function putvalue requires the DIO object and the values to be written as input arguments You can specify the values to be written as a decimal value or as a binary vector binvec A binary vector is a logical array that is constructed with the least significant bit LSB in the first column and the most significant bit MSB in the last column For example the decimal value 23 is written in binvec notation as 1 1101 2 2 2 24 You might find that binvecs are easier to work with than decimal values because there is a clear association between a given line and the value 1 or 0 that is written to it You can convert decimal values to binvec values with the dec2binvec function For example suppose you create the digital I O object dio and add eight output lines to it from port 0 dio digitalio nidaq 1 addline dio 0 7 out To write a value of 23 to the eight lines contained by dio you can write to the device object data 23 putvalue dio data Alternatively you can write to individual lines through the Line property putvalue dio Line 1 8 data Writing and Reading Digital O Line Values To write a binary vector of values using the device object and the Line property bvdata dec2binvec data 8 putvalue dio bvdata putvalue dio Line 1 8 bvdata The second input argument supplied to dec2binvec specifies the number of bits used to represent the decimal value Because
211. digitized data that can be read by the computer There are two ways to manage acquired data e Preview the data with the peekdata function e Extract the data from the engine with the getdata function After data is extracted from the engine you can analyze it save it to disk etc In addition to these two functions there are several properties associated with managing acquired data These properties are listed below Table 5 5 Analog Input Data Management Properties Property Name Description SamplesAcquired Indicate the number of samples acquired per channel SamplesAvailable Indicate the number of samples available per channel in the data acquisition engine SamplesPerTrigger Specify the number of samples to acquire for each channel group member for each trigger that occurs Previewing Data Before you extract and analyze acquired data you might want to examine preview the data as it is being acquired Previewing the data allows you to determine if the hardware is performing as expected and if your acquisition process is configured correctly Once you are convinced that your system is in order you might still want to monitor the data even as it is being analyzed or saved to disk Previewing data is managed with the peekdata function For example to preview the most recent 1000 samples acquired for the analog input object ai data peekdata ai 1000 Managing Acquired Data After start is issued you ca
212. do this you should connect a known signal such as that produced by a function generator to the module You then configure the input parameters as shown below fig Input Setup Ox i F7 All Channels Identical occ Di Chan Number fal Trigger OFF Range fio Trig Mode level J Coupling DC Coupling Trig Level ic Grounding On Breakout Box e Hysteresis jo Digital AntiAlas ON 7 Trig Slope Pos Exit Analog Anti Alias Not Adjustable OK Cancel A Troubleshooting Your Hardware The result of such a test is shown below for channel 1 ia HP E1432A Soft Front Panel If the Soft Front Panel does not provide you with the expected results for the module under test and you are sure that your test setup is configured correctly then the problem is probably with the hardware To get support for your Agilent Technologies hardware visit their Web site at http www agilent com A 4 Measurement Computing Hardware Measurement Computing Hardware If you are having trouble using the Data Acquisition Toolbox with a supported Measurement Computing board the reason might be that e You are using a hardware driver that is incompatible with the toolbox e Your hardware is not functioning properly What Driver Are You Using The Data Acquisition Toolbox is compatible only with specific versions of the the Universal Library drivers or the associated release of the InstaCal software and is not guara
213. documentation and depends on the specific board you are using and your platform configuration Vendor Keithley Measurement Computing National Instruments Usage AI AO Common Access Read write Data type String Read only Yes when running Keithley DMA Transfer data using a single DMA channel Interrupts Transfer data using interrupts If bus mastering is disabled in the DriverLINX configuration panel for the device then DMA is not available and the default is set to Interrupts Measurement Computing Default The transfer mode is automatically selected by the driver based on the board type and the sampling rate InterruptPer Transfer single data points using interrupts Point DMA Transfer data using a single DMA channel AI only InterruptPer Transfer a block of data using interrupts AI only Block TransferMode National Instruments Interrupts Transfer data using interrupts SingleDMA Transfer data using a single DMA channel DualDMA Transfer data using two DMA channels This default property value is supplied by the driver For most devices that support data transfer via interrupts and DMA SingleDMA is the default value 12 37 TransferMode 12 38 Troubleshooting Your Hardware This appendix describes simple tests you can perform to troubleshoot your National Instruments Measurement Computing Agilent Technologies and sound card hardware The tests involve using software provided by
214. does not support this mode or you don t have the correct driver installed If your card supports full duplex mode then you might need to enable this feature through the Multimedia Properties dialog box Refer to Sound Cards on page A 11 for a picture of this dialog box If you are unsure about the full duplex capabilities of your sound card refer to its specification sheet or user manual It is usually very easy to update your hardware drivers to the latest version by visiting the vendor s Web site A Troubleshooting Your Hardware Other Things to Try If troubleshooting your hardware does not help you then you might need to register the hardware driver adaptor or contact The MathWorks for support Registering the Hardware Driver Adaptor When you first create a device object the associated hardware driver adaptor is automatically registered so that the data acquisition engine can make use of its services The hardware driver adaptors included with the toolbox are all located in the daq private directory The full name for each adaptor is shown below Table A 1 Supported Vendors Device Types and Full Adaptor Names Vendor Device Type Full Adaptor Name Agilent Technologies mwhpe1432 d11 Measurement Computing mwmcc dll Keithley mwkeithley d1l National Instruments mwnidaq d11l Parallel ports mwparallel d1l Windows sound cards mwwinsound d1l If for some reason a toolbox adaptor is not automatically registered
215. dx muxchanidx ai 193 See Also Functions addmuxchannel 10 75 obj2mfile Purpose Syntax Arguments Description 10 76 Convert device objects channels or lines to MATLAB code obj2mfile obj file obj2mfile obj file syntax obj2mfile obj file all obj2mfile obj file syntax all obj A device object array of device objects channels or lines file The file that the MATLAB code is written to The full pathname can be specified If an extension is not specified the m extension is used syntax Syntax of the converted MATLAB code By default the set syntax is used If dot is specified then the subscripted referencing syntax is used If named is specified then named referencing is used if defined all If all is specified all properties are written to file If all is not specified only properties that are not set to their default values are written to file obj2mfile obj file converts obj to the equivalent MATLAB code using the set syntax and saves the code to file By default only those properties that are not set to their default values are written to file obj2mfile obj file syntax converts obj to the equivalent MATLAB code using syntax and saves the code to file The values for syntax can be set dot or named set uses the set syntax dot uses subscripted assignment dot notation and named uses named referencing if defined obj2mfile obj file all
216. e set ai SamplesPerTrigger ActualRate set ai LoggingMode Disk amp Memory set ai LogFileName data daq start ai After the data has been collected and saved to a disk file you can retrieve the data and other acquisition related information using daqread To read all the sample time pairs from data daq data time daqread data daq daqread See Also To read samples 500 to 1000 for all channels from data daq data daqread data daq Samples 500 1000 To read the first 0 5 seconds of data for channels 1 and 2 from data daq data daqread data daq Time 0 0 5 Channels 1 2 To obtain the channel property information from data daq daqinfo daqread data daq info chaninfo daqinfo ObjInfo Channel To obtain a list of event types and event data contained by data daq daqinfo daqread data daq info events dagqinfo ObjInfo EventLog event_type events Type event_data events Data Functions getdata Properties EventLog LogFileName LoggingMode LogToDiskMode 10 43 daqregister Purpose Syntax Arguments Description Remarks Example 10 44 Register or unregister a hardware driver adaptor daqregister adaptor daqregister adaptor unload out daqregister adaptor The hardware driver adaptor name The supported adaptors are hpe1432 keithley mcc nidaq parallel and winsound unload Specifies that the
217. e 0K canei apoy Her the new display in the Oscilloscope To show a trace in a particular display use the Channel Display pane of the Channel Editor GUI To open this GUI select Channel from the Edit menu As shown below CHO is associated with the new display Channel Editor x Channel Channel Properties Channel Display Configure the display for each channel Associate the new display with CHO Click the OK or Apply button to update the Oscilloscope 9 5 9 softscope The Data Acquisition Oscilloscope The Oscilloscope is now configured so that the CHO trace is shown in the bottom display and the CH1 trace is shown in the top display Oscilloscope 1 Efer o x File Edit Help Channel Scaling Triggers Horizontal Acquire Continuous z Offset Scale Samples to acquire J Fillthe display C Count foo Vertical CH1 5 0Vidiv 10 0msidiv cH CY Type independent x CH1 Har Offset Scale a D CHO 7 4850Vidiv 10 0msidiv On Trigger Configuring Display Properties You can change the display characteristics of the Oscilloscope by configuring display properties You access the display properties these two ways e Property Inspector Place the mouse cursor in the display of interest right click and select Edit Properties from the menu e Scope Editor GUI Select Scope from the Edit menu and then choose the Scope Properti
218. e Read only N A when running The default value is device specific Functions daqhwinfo daqread getdata putdata Properties InputRange NativeOffset OutputRange 11 55 OutputRange Purpose Description Characteristics Values Example 11 56 Specify the range of the analog output hardware subsystem OutputRange is a two element vector that specifies the range of voltages that can be output by the analog output AO subsystem You should configure OutputRange so that the maximum dynamic range of your hardware is utilized For many devices the output range is expressed in terms of the gain and polarity AO subsystems have a finite number of OutputRange values that you can set If an output range is specified but does not match a valid range then the next highest supported range is automatically selected by the engine If OutputRange exceeds the range of valid values then an error is returned Use the daqhwinfo function to return the output ranges supported by your board Because the engine can set the output range to a value that differs from the value you specify you should return the actual output range for each channel using the get function or the device object display summary Alternatively you can use the setverify function which sets the OutputRange value and then returns the actual value that is set Usage AO Channel Access Read write Data type Two element vector of doubles Read only Yes whe
219. e delete Properties HwLine Index 11 43 LineName Purpose Description Characteristics Values Example See Also 11 44 Specify a descriptive line name LineName specifies a descriptive name for a hardware line If a line name is defined then you can reference that line by its name If a line name is not defined then the line must be referenced by its index Line names are not required to be unique You can also define descriptive line names when lines are added to a digital I O object with the addline function Usage DIO Line Access Read write Data type String Read only Yes when running The default value is an empty string To reference a line by name it must contain only letters numbers and underscores and must begin with a letter Create the digital I O object dio and add four hardware lines to it dio digitalio nidaq 1 addline dio 0 3 out To assign a descriptive name to the first line contained by dio line1 dio Line 1 set line1 LineName Joe You can now reference this line by name instead of index set dio Joe Direction In Functions addline LogFileName Purpose Specify the name of the disk file to which information is logged Description You can log acquired data device object property values and event information and hardware information to a disk file by setting the LoggingMode property to Disk or Disk amp Memory You can specify any value for
220. e Save Softscope dialog box is shown below Save in J Work E A censusfit m File name mec si Save as type a Files ia Cancel To load a softscope file into the Oscilloscope provide the file name as an argument to the softscope function softscope mcc si 9 25 9 softscope The Data Acquisition Oscilloscope 9 26 Function Reference This chapter describes the toolbox M file functions that you use directly Note that a number of other M file helper functions are provided with this toolbox to support the functions listed below These helper functions are not documented because they are not intended for direct use The sections are as follows Getting Command Line Function Help p 10 2 Functions By Category p 10 3 Functions Alphabetical List p 10 7 How to use the daghelp and help functions to return toolbox function help and a brief discussion of overloaded functions Contains a series of tables that group functions by category Lists all the functions alphabetically 10 Function Reference Getting Command Line Function Help To get command line function help you should use the daqhelp function For example to get help for the addchannel function type daqhelp addchannel Alternatively you can use the help command help addchannel However the Data Acquisition Toolbox provides overloaded versions of several MATLAB functions That is it p
221. e an associated callback property Callback functions are M file functions that you construct to suit your specific data acquisition needs You execute a callback when a particular event occurs by specifying the name of the M file callback function as the value for the associated callback property Refer to Creating and Executing Callback Functions on page 5 51 to learn how to create callback functions Note that daqcallback is the default value for some callback properties Event Types The analog output event types and associated callback properties are described below Table 6 9 Analog Output Callback Properties Event Type Property Name Run time error RuntimeErrorFen Samples output SamplesOutputFen SamplesOutputFcnCount Start StartFen Stop StopFen Timer TimerFen TimerPeriod Trigger TriggerFen Events and Callbacks Run time Error Event A run time error event is generated immediately after a run time error occurs This event executes the callback function specified for RuntimeErrorFcn Additionally a toolbox error message is automatically displayed to the MATLAB workspace If an error occurs that is not explicitly handled by the toolbox then the hardware specific error message is displayed The default value for RunTimeErrorFcn is daqcallback which displays the event type the time the event occurred the device object name and the error message Run time errors include hardware errors and timeouts Ru
222. e if a line was passed if isdioline line error The argument passed is not a line end You can examine the Data Acquisition Toolbox M files for examples that use isdioline Functions isvalid isvalid Purpose Syntax Arguments Description Remarks Example Determine whether device objects channels or lines are valid out isvalid obj out isvalid obj Channel index out isvalid obj Line index obj A device object or array of device objects obj Channel index One or more channels contained by obj obj Line index One or more lines contained by obj out A logical array out isvalid obj returns a logical 1 to out if obj is a valid device object Otherwise a logical 0 is returned out isvalid obj Channel index returns a logical 1 to out if the channels specified by obj Channel index are valid Otherwise a logical 0 is returned out isvalid obj Line index returns a logical 1 to out if the lines specified by obj Line index are valid Otherwise a logical 0 is returned Invalid device objects channels and lines are no longer associated with any hardware and should be cleared from the workspace with the clear function Typically you use isvalid directly only when you are creating your own M files Create the analog input object ai for a National Instruments board and add eight channels to it analoginput nidaq 1 addchannel ai 0 7 ai ch To verify the device ob
223. e maximum sampling rate of your hardware you should set ChannelSkewMode to Equisamp1e Usage AI Common Access Read write Data type String Read only Yes when running ChannelSkewMode Values Agilent Technologies and Sound Cards None This is the only supported value for SS H hardware Keithley and National Instruments Minimum The channel skew is set to the minimum supported value Equisample The channel skew is given by sampling rate number of channels Manual The channel skew is given by ChannelSkew Measurement Computing Minimum The channel skew is set to the minimum supported value Equisample The channel skew is given by sampling rate number of channels 1 Example Create an analog input object for Keithley s KPCI 3108 board and add eight channels ai analoginput keithley 10 addchannel ai 0 7 Using the default Channe1SkewMode value of Min and the default SampleRate value of 1000 the corresponding Channe1Skew value is ai ChannelSkew ans 1 0000e 005 To use the maximum sampling rate set ChannelSkewMode to Equisample ai ChannelskewMode Equi ai Samplerate 100000 8 See Also Properties ChannelSkew SampleRate 11 23 ClockSource Purpose Description Characteristics Values 11 24 Specify the clock used to govern the hardware conversion rate For all supported hardware except Measurement Computing analog output subsystems ClockSource can be set
224. e the use of immediate manual and software triggers Analog Output Demos The analog output demos are listed below Demo Name Description daqfcngen dagqplay daqsong demoao_channel demoao_intro demoao_trig Example function generator Output data to the specified adaptor Output data from HANDEL MAT to a sound card Introduction to analog output channels Introduction to analog output objects Demonstrate the use of immediate and manual triggers 2 15 2 Getting Started with the Data Acquisition Toolbox Digital O Demos The digital I O demos are listed below Demo Name Description demodio_intro Introduction to digital I O objects demodio_line Introduction to digital I O lines diopanel Example panel for transferring values between MATLAB and a digital I O subsystem 2 16 Examining Your Hardware Resources Examining Your Hardware Resources You can examine the data acquisition hardware resources visible to the toolbox with the daghwinfo function Hardware resources include installed boards hardware drivers and adaptors The information returned by daqhwinfo depends on the supplied arguments and is divided into these three categories e General toolbox information e Adaptor specific information Device object information If you configure hardware parameters using a vendor tool such as National Instruments Measurement and Automation Explorer or Measurement Computing
225. e this allocation How Much Memory Do You How to determine the memory required for your acquisition needs Need p B 3 Example Managing An example using a sound card that illustrates how the toolbox Memory Resources p B 4 allocates memory B Managing Your Memory Resources B 2 Memory Allocation When data is acquired from an analog input subsystem or output to an analog output subsystem it must be temporarily stored in computer memory The Data Acquisition Toolbox allocates memory in terms of data blocks A data block is defined as the smallest slice of memory that the data acquisition engine can usefully manipulate For example acquired data is logged to a disk file using an integral number of data blocks A representation of allocated memory using n data blocks is shown below block 1 block 2 blocks l TE l baka The Data Acquisition Toolbox strives to make memory allocation as simple as possible For this reason the data block size and number of blocks are automatically calculated by the engine This calculation is based on the parameters of your acquisition such as the sampling rate and is meant to apply to most common data acquisition applications Additionally as data is acquired the number of blocks dynamically increases up to a predetermined limit However the engine cannot guarantee that the appropriate block size number of blocks or total memory is allocated under these conditions
226. e units in which trigger delay data is measured TriggerDelayUnits can be Seconds or Samples If TriggerDelayUnits is Seconds then data logging is delayed by the specified time for each channel group member If TriggerDelayUnits is Samples then data logging is delayed by the specified number of samples for each channel group member The trigger delay value is given by the TriggerDelay property Usage Access Data type Read only when running Seconds Samples Properties TriggerDelay AI Common Read write String Yes The trigger is delayed by the specified number of seconds The trigger is delayed by the specified number of samples TriggerRepeat Purpose Description Characteristics Values See Also Specify the number of additional times the trigger executes You can configure a trigger to occur once one shot acquisition or multiple times If TriggerRepeat is set to its default value of zero then the trigger executes once If TriggerRepeat is set to a positive integer value then the trigger executes the specified number of times If TriggerRepeat is set to inf then the trigger executes continuously until a stop function is issued or an error occurs You can quickly evaluate how many triggers have executed by examining the TriggersExecuted property or by invoking the display summary for the device object The display summary is invoked by typing the device object name at the MATLAB command line
227. ead only property values are not saved Therefore read only properties use their default values when you load the device object into the MATLAB workspace To determine if a property is read only use the propinfo function or examine the property reference pages Save property values using the set syntax the dot notation or named referencing if defined If the UserData property is not empty or if a callback property is set to a cell array of values or a function handle then the data stored in these properties is written to a MAT file when the device object is saved The MAT file has the same name as the M file containing the device object code For example suppose you create the analog input object ai for a sound card add two channels to it and configure several property values ai analoginput winsound addchannel ai 1 2 Temp1 Temp2 time now set ai SampleRate 11025 TriggerRepeat 4 set ai TriggerFcn mycallback time start ai 8 2 Saving and Loading Device Objects The following command saves ai and the modified property values to the M file myai m Because the TriggerFcn property is set to a cell array of values its value is automatically written to the MAT file myai mat obj2mfile ai myai m Created d v6 myfiles myai m Created d v6 myfiles myai mat Use the type command to display myai m at the command line Loading the Device Object To load a device object that was save
228. ect Create the analog input object AI for a sound card The installed adaptors and hardware IDs are found with daqhwinfo AI analoginput winsound SAI analoginput nidaq 1 AI analoginput mcc 1 X Managing Acquired Data 2 Add channels Add one hardware channel to AI chan addchannel AI 1 chan addchannel AI 0 For NI and MCC 3 Configure property values Define a 10 second acquisition set up the plot and store the plot handle in the variable P The amount of data to display is given by preview duration 10 Ten second acquisition set AI SampleRate 8000 ActualRate get AI SampleRate set AI SamplesPerTrigger duration ActualRate preview duration ActualRate 100 subplot 211 set gcf doublebuffer on P plot zeros preview 1 grid on title Preview Data xlabel Samples ylabel Signal Level Volts 4 Acquire data Start AI and update the display using peekdata every time an amount of data specified by preview is stored in the engine by polling SamplesAcquired The drawnow command forces MATLAB to update the plot After all data is acquired it is extracted from the engine Note that whenever peekdata is used all acquired data might not be displayed start AI while AI SamplesAcquired lt preview end while AI SamplesAcquired lt duration ActualRate data peekdata AI preview set P ydata data drawnow end Extract all the acquire
229. ect AlVoice for a sound card The installed adaptors and hardware IDs are found with daqhwinfo AIVoice analoginput winsound AIVoice analoginput nidaq 1 AIVoice analoginput mcc 1 2 Add channels Add one hardware channel to AlVoice chan addchannel AIVoice 1 chan addchannel AIVoice 0 For NI and MCC 3 Configure property values Define a 1 second total acquisition time and configure a software trigger The source of the trigger is chan and the trigger executes when a rising voltage level has a value of at least 0 2 volt Additionally the trigger is repeated once when the trigger condition is met duration 0 5 One half second acquisition for each trigger set AIVoice SampleRate 44100 ActualRate get AIVoice SampleRate set AIVoice Timeout 5 set AIVoice SamplesPerTrigger ActualRate duration set set AIVoice TriggerChannel chan set AIVoice TriggerType Software set AIVoice TriggerCondition Rising set AIVoice TriggerConditionValue 0 2 AlVoice TriggerRepeat 1 Configuring Analog Input Triggers 4 Acquire data Start AlVoice acquire the specified number of samples extract all the data from the first trigger as sample time pairs and extract all the data from the second trigger as sample time pairs Note that you can extract the data acquired from both triggers with the command getdata AIVoice 44100 start AIVoice
230. ected to the positive amplifier socket labeled and the ground is connected to the negative amplifier socket labeled Amplifier Input signal Ground out National Instruments suggests that you can use single ended inputs under any of these conditions e The input signal is high level greater than 1 volt e The leads connecting the signal are less than 10 feet e The input signal can share a common reference point with other signals You should use differential input connectors for any input signal that does not meet the preceding conditions You can configure many National Instruments boards for two different types of single ended connections e Referenced single ended RSE connection The RSE configuration is used for floating signal sources In this case the hardware device itself provides the reference ground for the input signal e Nonreferenced single ended NRSE connection The NRSE input configuration is used for grounded signal sources In this case the input signal provides its own reference ground and the hardware device should not supply one Refer to your National Instruments hardware documentation for more information about RSE and NRSE connections 1 25 T introduction to Data Acquisition 1 26 Transferring Data from Hardware to System Memory The transfer of acquired data from the hardware to system memory follows these steps 1 Acquired data is stored in the hardware s first
231. ed Vendors Device Types and Adaptor Names Vendor Device Type Adaptor Name Agilent Technologies hpe1432 Keithley keithley Measurement Computing mcc National Instruments nidaq Parallel port parallel Windows sound cards winsound Note To interface unsupported hardware devices to the toolbox use the Data Acquisition Toolbox Adaptor Kit which is installed with the toolbox To get started with the adaptor kit read the Data Acquisition Toolbox Adaptor Kit User s Guide As described in Examining Your Hardware Resources on page 2 17 you can list the supported adaptor names with the daqhwinfo function 2 7 2 Getting Started with the Data Acquisition Toolbox 2 8 Accessing Your Hardware Perhaps the most effective way to get started with the Data Acquisition Toolbox is to connect to your hardware and input or output data This section provides simple examples that show you how to e Acquire data from analog input channels e Output data to analog output channels e Read values from and write values to digital I O lines Each example illustrates a typical data acquisition session The data acquisition session comprises all the steps you are likely to take when acquiring or outputting data using a supported hardware device You should keep these steps in mind when constructing your own data acquisition applications Note that the analog input and analog output examples use a sound card while the digital I O exa
232. ed for input or output When adding hardware lines to a digital I O object with addline you must configure the line direction The line direction can be In or Out and is automatically stored in Direction If a line direction is In you can only read a value from that line If a line direction is Out you can write or read a line value For line configurable devices you can change individual line directions using Direction For port configurable devices you cannot change individual line directions Usage DIO Line Access Read write Data type String Read only Yes when running In The line can be read from Out The line can be read from or written to Create the digital I O object dio and add two input lines and two output lines to it dio digitalio nidaq 1 addline dio 0 3 In In Out Out To configure all lines for output dio Line 1 2 Direction Out Functions addline EventLog Purpose Description Store information for specific events Eventlog isa structure array that stores information related to specific analog input AI or analog output AO events Event information is stored in the Type and Data fields of EventLog Type stores the event type The logged event types are shown below Event Type Description Al AO Data missed Data is missed by the engine Input overrange A signal exceeds the hardware input range Run time error A run time error is encountered Run time
233. ed with the LogToDiskMode property If LogToDiskMode is Overwrite the log file is overwritten If LogToDiskMode is Index new log files are created each with an indexed name based on the value of LogFileName Specifying a Filename You specify the name of the log file with the LogFileName property You can specify any value for LogFileName including a directory path provided the filename is supported by your operating system Additionally if LogToDiskMode is Index then the log filename also follows these rules e Indexed log filenames are identified by a number This number precedes the filename extension and is incremented by one for successive log files e If no number is specified as part of the initial log filename then the first log file does not have a number associated with it For example if LogFileName is myfile daq then myfile daq is the name of the first log file myfileO1 daq is the name of the second log file and so on LogFileName is updated after the log file is written after the stop event occurs e If the specified log filename already exists then the existing file is overwritten Logging Information to Disk Retrieving Logged Information You retrieve logged information with the daqread function You can retrieve any part of the information stored in a log file with one call to daqread However you will probably use daqread in one of these two ways e Retrieving data and time information e Retrievin
234. eding section has the MATLAB indices 1 through 8 automatically assigned to the hardware lines 0 through 7 respectively To swap the first two hardware lines so that line ID 1 is the LSB you can supply the appropriate index to hwlines and use the HwLine property hwlines 1 HwLine 1 hwlines 2 HwLine 0 7 9 7 Digital Input Output 7 10 Alternatively you can use the Line property dio Line 1 HwLine 1 dio Line 2 HwLine 0 Descriptive Line Names Choosing a unique descriptive name can be a useful way to identify and reference lines particularly for large line groups You can associate descriptive names with hardware lines with the addline function For example suppose you want to add 8 lines to dio and you want to associate the name TrigLine with the first line added addline dio 0O out TrigLine addline dio 1 7 out Alternatively you can use the LineName property addline dio 0 7 out dio Line 1 LineName TrigLine You can now use the line name to reference the line dio TrigLine Direction in Example Adding Lines for National Instruments Hardware This example illustrates various ways you can add lines to a DIO object associated with a National Instruments AT MIO 16DE 10 board This board is a multiport device whose characteristics are described in Line and Port Characteristics on page 7 5 To add eight input lines to dio from port 0 addline dio 0 7 in To add f
235. ee below When adding channels to an analog input object you must follow these rules e The channels must reside on the same hardware device You cannot add channels from different devices or from different subsystems on the same device e The channels must be sampled at the same rate You add channels to an analog input object with the addchannel function addchannel requires the device object and at least one hardware channel ID as input arguments You can optionally specify MATLAB indices descriptive channel names and an output argument For example to add two hardware channels to the device object ai created in the preceding section chans addchannel ai 0 1 The output argument chans is a channel object that reflects the channel array contained by ai You can display the class of chans with the whos command whos chans Name Size Bytes Class chans 2x1 512 aichannel object Grand total is 7 elements using 512 bytes You can use chans to easily access channels For example you can easily configure or return property values for one or more channels As described in Referencing Individual Hardware Channels on page 4 5 you can also access channels with the Channel property 4 3 4 Getting Started with Analog Input 4 4 Once you add channels to an analog input object the properties listed below are automatically assigned values These properties provide descriptive information about the channels based on their
236. el number x data type Of course the number of samples you need to store in the engine at any time depends on your particular needs The memory used by a device object is given by the formula memory used block size x block number x channel number x data type The block size and block number are given by the BufferingConfig property The data type is given by the NativeDataType field of the daqhwinfo function You can display the memory resources used by and available to a device object with the daqmem function For analog input objects memory is used when channels are added For analog output objects memory is used when data is queued in the engine For both device objects the memory used can dynamically change based on the number of samples acquired or queued B 3 B Managing Your Memory Resources B 4 Example Managing Memory Resources Suppose you create the analog input object ai for a sound card add two channels to it and configure a four second acquisition using a sampling rate of 11 025 kHz ai analoginput winsound addchannel ai 1 2 set ai SampleRate 11025 set ai SamplesPerTrigger 44100 You return the default block size and number of blocks with the Buf feringConfig property get ai BufferingConfig ans 1024 30 You return the memory resources with the daqmem function daqmem ai ans UsedBytes 122880 MaxBytes 18011136 The UsedBytes field tells you how much memory is
237. en the MATLAB indices define the scan order index 1 is sampled first index 2 is sampled second and so on For digital I O objects the diagram would look the same except that lines would be substituted for channels 3 The Data Acquisition Session Configuring and Returning Properties You define and evaluate the behavior of your data acquisition application with device object properties You define your application behavior by assigning values to properties with the set function or the dot notation You evaluate your application configuration and status by displaying property values with the get function or the dot notation Property Types Data Acquisition Toolbox properties are divided into two main types e Common properties Common properties apply to every channel or line contained by a device object e Channel Line properties Channel line properties are configured for individual channels or lines The relationship between an analog input object the channels it contains and their properties is shown below Analog Input Object Common properties apply to all channels Channel 1 Channel 2 Channel 3 Channel properties are set on a per channel basis Channel n For digital I O objects the diagram would look the same except that lines would be substituted for channels Configuring and Returning Properties Common properties and channel line properti
238. en the analog signal enters the specified range of values Note that when TriggerType is HwAnalog the trigger condition values are all specified as two element vectors Setting two trigger levels prevents the module from triggering repeatedly because of a noisy signal 5 37 5 Doing More with Analog Input 5 38 Hardware Digital Triggering If TriggerType is HwDigital the trigger is given by a digital TTL signal For example to trigger your acquisition when the negative edge of a digital signal is detected ai analoginput hpe1432 8 addchannel ai 1 16 set ai TriggerType HwDigital set ai TriggerCondition NegativeEdge Hardware Analog Triggering If TriggerType is HwAnalog the trigger is given by an analog signal For example to trigger your acquisition when the trigger signal is between 4 volts and 4 volts ai analoginput hpe1432 8 addchannel ai 1 16 set ai TriggerType HwAnalog set ai TriggerCondition Entering set ai TriggerConditionValue 4 0 4 0 set ai TriggerChannel ai Channel 1 4 Configuring Analog Input Triggers Measurement Computing When using Measurement Computing hardware there are additional trigger types and trigger conditions available to you These device specific property values fall into two categories hardware digital triggering and hardware analog triggering The device specific trigger types and trigger conditions are descr
239. ending 3 22 status evaluation AI object 4 21 AO object 6 13 DIO object 7 20 stereo mode 4 7 stop event AI object 5 47 AO object 6 27 stop function 10 105 StopFcen property 11 77 StopTriggerChannel property 12 27 StopTriggerCondition property 12 28 StopTriggerConditionValue property 12 30 StopTriggerDelay property 12 31 StopTriggerDelayUnits property 12 32 StopTriggerType property 12 33 Sum property 12 34 synchronizing triggers 11 49 T Tag property 11 79 third party adaptors A 19 time absolute 5 18 initial trigger 5 18 relative 5 17 Timeout property 11 80 timer event AI object 5 47 AO object 6 27 DIO object 7 17 TimerFcn property 11 81 TimerPeriod property 11 82 toolbox components data acquisition engine 2 4 hardware driver adaptor 2 7 M files 2 3 transducer 1 3 TransferMode property 12 35 trigger event AI object 5 47 AO object 6 28 trigger function 10 107 TriggerChannel property 11 84 TriggerCondition property 11 85 TriggerConditionValue property 11 90 TriggerDelay property 11 91 TriggerDelayUnits property 11 92 triggered acquisition 5 19 output 6 20 TriggerFcn property 11 83 TriggerRepeat property 11 93 triggers delays 5 25 Oscilloscope 9 14 postriggers 5 27 pretriggers 5 26 repeating 5 29 samples acquired for each trigger 4 11 synchronizing for AI and AO 11 49 times AI object 5 36 AO object 6 23 initial trigger 5 18 trigger conditions AI 5 20 Index trigger types AI object 5 20 AO ob
240. ensor e The range of your analog input hardware For many devices this range is specified by the gain and polarity You can return valid input ranges with the daghwinfo function e The engineering units associated with your acquisition By default most analog input hardware converts data to voltage values However after the data is digitized you might want to define a linear scaling that represents specific engineering units when data is returned to MATLAB The properties associated with engineering units and linearly scaling acquired data are given below Table 5 13 Analog Input Engineering Units Properties Property Name Description SensorRange Specify the range of data you expect from your sensor InputRange Specify the range of the analog input subsystem Units Specify the engineering units label UnitsRange Specify the range of data as engineering units Note If supported by the hardware you can set the engineering units properties on a per channel basis Therefore you can configure different engineering unit conversions for each hardware channel 5 55 5 Doing More with Analog Input 5 56 Linearly scaled acquired data is given by the formula scaled value A D value units range sensor range Note The above formula assumes you are using symmetric units range and sensor range values and represents the simplest scenario If your units range or sensor range values are asymmetric then you mus
241. ent Measurement Properties Measurement Type Define a new measurement Channel CH0 ad Type Vert Add Click Add to add the measurement to the table Type Pk2Pk Delete Click OK or Apply to add the Beal canei a e measurement to the Oscilloscope Select the channel and the measurement type Defined measurements Channel M CH0 Making Measurements After you click the OK or Apply button of the Measurement Editor the Measurements panel is automatically added to the Oscilloscope You can then click the Add Measurement button to define additional measurements Oscilloscope E 5 o x File Edit Help Channel Scaling Triggers Measurements ee Rae Acquire Jone Shot gt Channel CHO Samples to acquire Type Pk2Pk A x C Fill the display Value 7 48516 Count hooo tt M Show in Display Vertical CHO Type dependent x Channel CHO Offset Scale Condition Rising x Value 0 00801 V Show in Display Value fa3 alueZ p Pretrigger 0 02 sec Trigger oo TE The vertical cursor To add a new measurement to the panel click Add Measurement CHO 2 57 30Vidiv 5 0037 msidiv Add Measurement Defining a New Measurement Type You define a new measurement type by defining a MATLAB function that takes an array of data as input and returns a scalar value You can defi
242. equired DIO object contains line s Index LineName HwLine Port Direction 1 0 0 In 2 a 1 0 In Line display se pees summary 7 3 2 0 In 4 3 0 In 5 7 4 0 In 6 ce 5 0 In 7 na 6 0 In 8 7 7 0 In You can use the Line property to display only the line summary information DIO Line 7 21 7 Digital Input Output 7 22 Saving and Loading the Session This chapter describes how to save and load information associated with a data acquisition session The sections are as follows Saving and Loading Device Save device objects and their associated property values to disk as an Objects p 8 2 M file or as a MAT file Logging Information to Log acquired data device objects and hardware and event information Disk p 8 5 to disk 8 Saving and Loading the Session Saving and Loading Device Objects You can save a device object to disk using two possible formats e As an M file using the obj2mfile function e As a MAT file using the save command For analog input objects you can also save acquired data hardware information and so on to a log file Refer to Logging Information to Disk on page 8 5 for more information Saving Device Objects to an M File You can save a device object to an M file using the obj2mfile function obj2mfile provides you with these options e Save all property values or save only those property values that differ from their default values R
243. er internal noise or it can be added to the signal as it travels down the input wires to the amplifier external noise Techniques that you can use to reduce the effects of noise are described below Removing Internal Noise Internal noise arises from thermal effects in the amplifier Amplifiers typically generate a few microvolts of internal noise which limits the resolution of the signal to this level The amount of noise added to the signal depends on the bandwidth of the input amplifier To reduce internal noise you should select an amplifier with a bandwidth that closely matches the bandwidth of the input signal Removing External Noise External noise arises from many sources For example many data acquisition experiments are subject to 60 Hz noise generated by a c power circuits This type of noise is referred to as pick up or hum and appears as a sinusoidal interference signal in the measurement circuit Another common interference source is fluorescent lighting These lights generate an arc at twice the power line frequency 120 Hz Noise is added to the acquisition circuit from these external sources because the signal leads act as aerials picking up environmental electrical activity Much of this noise is common to both signal wires To remove most of this common mode voltage you should Making Quality Measurements e Configure the input channels in differential mode Refer to Channel Configuration on page 1 23
244. eresis The trigger occurs when the analog signal is less than the specified low value with hysteresis given by the specified high value Configuring Analog Input Triggers Hardware Digital Triggering If TriggerType is HwDigital the trigger occurs when the falling edge of a digital TTL signal is detected The following example illustrates how to configure a hardware digital trigger ai analoginput nidaq 1 addchannel ai 0 7 set ai TriggerType HwDigital The diagram below illustrates how you connect a digital trigger signal to an MIO 16E Series board PFI0 TRIG1 corresponds to pin 11 TTL signal PFIO TRIG1 K MIO 16E Series board Hardware Analog Triggering If TriggerType is HwAnalogPin the trigger is given by a low range analog signal typically between 10 and 10 volts connected to the appropriate trigger pin For example to trigger your acquisition when the trigger signal is between 4 volts and 4 volts ai analoginput nidaq 1 addchannel ai 0 7 set ai TriggerType HwAnalogPin set ai TriggerCondition InsideRegion set ai TriggerConditionValue 4 0 4 0 If TriggerType is HwAnalogChannel the trigger is given by an analog signal and the trigger channel is the first channel in the channel group MATLAB index of one The valid range of the analog trigger signal is given by the full scale range of the trigger cha
245. error is returned Vendor Sound cards Usage AI AO Common Access Read write Data type String Read only Yes when running On The sample rate can be set only to a small set of standard values Off If supported by the hardware the sample rate can be set to any value within the allowed bounds up to a maximum of 96 0 kHz StopTriggerChannel Purpose Description Characteristics Values Example See Also Specify the analog input channel serving as a hardware stop trigger source StopTriggerChannel defines the channel number to be used for the HwAnalog setting of the StopTriggerType property The channel must be a member of the analog input channel list To associate a particular channel with the stop trigger assign the channel s hardware ID number to the property If you specify a channel object then an error is returned Vendor Keithley Usage AI Common Access Read write Data Type Double Read only Yes when running Any defined analog input channel The default value is an empty vector Create an analog input object for the Keithley KPCI 3108 board and add eight channels ai analoginput keithley 1 addchannel ai 0 7 Stop the acquisition when a falling voltage level of 0 1 volt is detected on the hardware channel with ID 2 ai StopTriggerType HwAnalog ai StopTriggerChannel 2 ai StopTriggerCondition Falling ai StopTriggerConditionValue 0 1 Properties StopTriggerCondit
246. erties To establish the device object behavior you assign values to properties using the set function or dot notation You can configure many of the properties at any time However some properties are configurable only when the device object is not running Conversely depending on your hardware settings and the requirements of your application you might be able to accept the default property values and skip this step 4 Acquire or output data To acquire or output data you must execute the device object with the start function While the device object is running it behaves according to the previously configured or default property values After data is acquired you must extract it from the engine with the getdata function Before you can output data you must queue it in the engine with the putdata function 5 Clean up When you no longer need the device object you should remove it from memory using the delete function and remove it from the MATLAB workspace using the clear command The data acquisition session is used in many of the documentation examples included in this guide Note that the fourth step is treated differently for digital VO objects because they do not store data in the engine Therefore only analog input and analog output objects are discussed in this section 3 2 Overview Example The Data Acquisition Session This example illustrates the basic steps you take during a data acquisition session
247. erties DataMissedFcn EventLog SamplesAvailable SamplesPerTrigger Timeout getsample Purpose Syntax Arguments Description Remarks Example See Also Immediately acquire one sample sample getsample obj obj An analog input object sample A row vector containing one sample for each channel contained by obj sample getsample obj immediately returns a row vector containing one sample for each channel contained by obj Using getsample is a good way to test your analog input configuration Additionally getsample does not store samples in or extract samples from the data acquisition engine e You can execute getsample at any time after channels have been added to obj e Except for sound cards you can use getsample on an analog input object that is not running Running is Off For sound cards the device object must be running Create the analog input object ai and add eight channels to it ai analoginput nidaq 1 ch addchannel ai 0 7 The following command returns one sample for each channel sample getsample ai Functions getdata peekdata 10 63 getvalue Purpose Syntax Arguments Description Remarks Example See Also 10 64 Read values from lines out getvalue obj out getvalue obj Line index obj A digital I O object obj Line index One or more lines contained by obj out A binary vector out getvalue obj returns the current va
248. erty Note that daqcallback is the default value for some callback properties Event Types The analog input event types and associated callback properties are described below Table 5 11 Analog Input Callback Properties Event Type Property Name Data missed DataMissedFcn Input overrange InputOverRangeFcn Run time error RuntimeErrorFcn Samples acquired SamplesAcquiredFen SamplesAcquiredFcnCount Start StartFen Stop StopFen Timer TimerFen TimerPeriod Trigger TriggerFen 5 Doing More with Analog Input 5 46 Data Missed Event A data missed event is generated immediately after acquired data is missed In most cases data is missed because e The engine cannot keep up with the rate of acquisition e The driver wrote new data into the hardware s FIFO buffer before the previously acquired data was read You can usually avoid this problem by increasing the size of the memory block with the Buf feringConfig property This event executes the callback function specified for the DataMissedFcn property The default value for DataMissedFcn is daqcallback which displays the event type and the device object name When a data missed event occurs the analog input object is automatically stopped Input Overrange Event An input overrange event is generated immediately after an overrange condition is detected for any channel group member An overrange condition occurs when an input signal exceeds the range specified by the
249. es The device specific Measurement Computing properties for analog input AI and analog output AO objects are given below Property Name Description Device Objects OutOfDataMode Specify how the value held by the analog AO output subsystem is determined TransferMode Specify how data is transferred from the AI AO data acquisition device to system memory National Instruments Properties The device specific National Instruments properties for analog input AI and analog output AO objects are given below Property Name Description Device Objects Coupling Specify the input coupling mode Al DriveAISenseTo Specify if AISENSE is driven to onboard Al Ground ground NumMuxBoards Specify the number of external multiplexer Al devices connected 12 5 12 Device Specific Property Reference 12 6 Property Name Description Device Objects OutOfDataMode Specify how the value held by the analog AO output subsystem is determined TransferMode Specify how data is transferred from the AI AO data acquisition device to system memory Parallel Port Properties The device specific parallel port properties are given below Property Name Description Device Objects BiDirectional Specify the BIOS control register bit that DIO Bit determines bidirectional operation PortAddress Indicate the base address of the parallel port DIO Sound Card Properties The device specific sound card propert
250. es e The Quick Reference Guide e Demos The Contents M File The Contents M file lists the toolbox functions and demos You can display this information by typing help daq Documentation Examples This guide provides detailed examples that show you how to acquire or output data These examples are collected in the example index which is available through the Help browser Some examples are constructed as mini applications that illustrate one or two important features of the toolbox and serve as templates so you can see how to build applications that suit your specific needs These examples are included as toolbox M files and are treated as demos You can list all Data Acquisition Toolbox demos by typing help daqdemos All documentation example M files begin with daqdoc To run an example type the M file name at the command line Note that most analog input AI and analog output AO examples are written for sound cards To use these examples with your hardware device you should modify the adaptor name and the device ID supplied to the creation function as needed Additionally most documentation examples are written for clocked subsystems However some supported hardware devices particularly Measurement Computing devices do not possess onboard clocks If the AI or Understanding the Toolbox Capabilities AO subsystem of your hardware device does not have an onboard clock then these examples will not work To use the
251. es are subdivided into these two categories e Base properties Base properties apply to all supported hardware subsystems of a given type such as analog input For example the SampleRate property is supported for all analog input subsystems regardless of the vendor Device specific properties Device specific properties apply only to specific hardware devices For example the BitsPerSample property is supported only for sound cards Note that base properties can have device specific values For example the InputType property has a different set of values for each supported hardware vendor The relationship between common properties channel line properties base properties and device specific properties is shown below Device object Base properties Common properties Device specific properties Hardware channels lines Base properties Channel line Device specific properties properties For a complete description of all properties refer to Chapter 11 Base Property Reference or Chapter 12 Device Specific Property Reference 3 13 3 The Data Acquisition Session Returning Property Names and Property Values Once the device object is created you can use the set function to return all configurable properties to a variable or to the command line Additionally if a property has a finite set of string values then set also return
252. es pane For this example use the Scope Editor GUI to change the color of both displays to white The steps are 1 Select both displays from the Select the scope components list 2 Open the color picker for the Color property 3 Select White from the color picker pop up menu 9 6 Displaying Channels The Scope Properties pane and color picker are shown below For descriptions of all display properties click the Help button Scope Editor x Scope Scope Properties Select both displays Channel Scaling v Editthe selected scope components properties Open the color picker and select ETHAN 5 White from the pop up menu HorizontalOffset 0 0 HorizontalScale 0 01 x HorizontalUnits 0 9412 1 0 902 a Custom Color L Layer bottom Black PixelsPerDivision 30 X L ShowAsScientific Faise ShowDataTip PE True OK Cancel ShowHorizontalvalue FE True Click Help to view property descriptions OK Cancel Help Math and Reference Channels In addition to hardware channels you can display e Reference channels The data associated with a reference channel is defined from a MATLAB variable or expression You should use reference channel data as a known waveform against which other data is compared e Math channels The data associated with a math channel is calculated in MATLAB using the data from existing hardware channels math channels
253. evice object then the assigned indices automatically start at one and increase monotonically If hardware lines have already been added to the device object then the assigned indices automatically start at the next highest index value and increase monotonically e The resulting indices begin at one and increase monotonically up to the size of the line group The first indexed line represents the least significant bit LSB and the highest indexed line represents the most significant bit MSB addline Example See Also More About Descriptive Line Names You can assign hardware lines descriptive names which are stored in the LineName property Choosing a unique descriptive name can be a useful way to identify and reference lines For a single call to addline you can e Specify one line name that applies to all lines that are to be added e Specify a different name for each line to be added If the number of names specified in a single addline call is more than one but differs from the number of lines to be added then an error is returned Ifa line is to be referenced by its name then that name must not contain symbols If you are naming a large number of lines then the makenames function might be useful If a line is not assigned a descriptive name then it must be referenced by index Create the digital I O object dio and add the first four hardware lines line IDs 0 3 from port 0 dio digitalio nidaq 1 addline di
254. evice object then the assigned indices automatically start at one and increase monotonically If hardware channels have already been added to the device object then the assigned indices automatically start at the next highest index value and increase monotonically e If index is specified but the indices are previously assigned then the requested assignment takes precedence and the previous assignment is reindexed to the next available values If the lengths of hwch and index are 10 9 addchannel 10 10 not equal then an error is returned and no channels are added to the device object e The resulting indices begin at one and increase monotonically up to the size of the channel group e If you are using scanning hardware then the indices define the scan order e Sound cards cannot be reindexed Rules for Adding Channels to National Instruments 1200 Series Boards When using National Instruments 1200 Series hardware you need to modify the above rules in these ways e Channel IDs are given in reverse order with addchannel For example to add eight single ended channels to the analog input object ai addchannel ai 7 1 0 e The scan order is from the highest ID to the lowest ID which must be 0 e There cannot be any gaps in the channel group e When channels are configured in differential mode the hardware IDs are 0 2 4 and 6 More About Descriptive Channel Names You can assign hardware channels descriptive names
255. f an S H circuit follows these steps 1 Ata given sampling instant the switch connects the buffer and capacitor to an input 2 The capacitor is charged to the input voltage 3 The charge is held until the A D converter digitizes the signal 4 For multiple channels connected multiplexed to one A D converter the previous steps are repeated for each input channel 5 The entire process is repeated for the next sampling instant T introduction to Data Acquisition A multiplexer S H circuit and A D converter are illustrated in the next section Hardware can be divided into two main categories based on how signals are sampled scanning hardware which samples input signals sequentially and simultaneous sample and hold SS H hardware which samples all signals at the same time These two types of hardware are discussed below Scanning Hardware Scanning hardware samples a single input signal converts that signal to a digital value and then repeats the process for every input channel used In other words each input channel is sampled sequentially A scan occurs when each input in a group is sampled once As shown below most data acquisition devices have one A D converter that is multiplexed to multiple input channels gt 2 Signal buffer Amplifier A D converter Input Multiplexer Sample and hold circuit channels Therefore if you
256. flects many of the basic setup properties described in Configuring Analog Input Properties on page 4 8 and is designed so you can quickly evaluate the status of your data acquisition session The display is divided into two main sections general information and channel information General Summary Information The general display summary includes the device object type and the hardware device name followed by this information e Acquisition parameters The sampling rate The number of samples to acquire per trigger The acquisition duration for each trigger The destination for logged data e Trigger parameters The trigger type The number of triggers including the number of triggers already executed e The engine status Whether the engine is logging data waiting to start or waiting to trigger The number of samples acquired since starting The number of samples available to be extracted with getdata Evaluating the Analog Input Object Status General display summary 7 Channel display summary Channel Summary Information The channel display summary includes property values associated with e The hardware channel mapping e The channel name e The engineering units The display summary for the example given in Acquiring Data with a Sound Card on page 4 14 before start is issued is shown below Display Summary of Analog Input AI Object Using AudioPCI Record Acquisition Parameters 8000 samples
257. for obj showdagevents obj index displays a summary of the events specified by index for obj showdagevents struct displays a summary of the events stored in the structure struct showdagevents struct index displays a summary of the events specified by index stored in the structure struct out showdagevents outputs the event information to a one column cell array out Each element of out is a string that contains the event information associated with that index value You can pass a structure of event information to showdagevents This structure can be obtained from the getdata function the dagqread function or the EventLog property showdagevents As shown below you can also display event information via the Workspace browser by right clicking a device object and selecting Explore gt Show DAQ Events from the context menu iix File Edit View Web Window Help aw a A By Stade Pze v e ai 1x1 1332 analoginput object 24 doub Open 1308 digi SZAL Display Summary Call Property Editor Select All Access context pop up menus by right clicking a device object Ready Display Hardware Info Events Import Data Save Selection As Save Workspace As DAQ Help Copy Delete Clear Workspace Rename Example Create the analog input object ai for a sound card add two channels and configure ai to execute three triggers ai analoginput winsound
258. from the Options menu The Properties dialog box is shown below for playback devices Select the appropriate device check box to enable playback Properties HE Mixer device AudioPCI Mixer Adjust volume for Playback C Recording ther z Show the following volume controls Volume Control v CD Wave Synthesizer wif Cancel To check if the CD and microphone are enabled for recording select the Recording radio button in the Properties dialog box and then select the appropriate device check box to enable recording The Properties dialog box is shown below for recording devices Properties i Lx Mixer device AudioPCI Mixer x Adjust volume for C Playback cD Microphone Line Auriliary A 13 A Troubleshooting Your Hardware The Recording Control panel is shown below You enable the CD or microphone for recording when the Select check box is checked for the CD Balance or Microphone Balance controls respectively E Recording Control Bik Options Help CD Microphone Line Balance Balance Balance e F H v FM e FI Volume Volume Volume T Select I Select AudioPCl Mixer Microphone and Sound Card Types Your microphone will be one of two possible types powered or unpowered You can use powered microphones only with Sound Blaster or Sound Blaster compatible micr
259. g AudioPCI Playback Output Parameters 8000 samples per second on each channel Trigger Parameters 1 Immediate trigger on START Engine status Waiting for START O total sec of data currently queued for START O samples currently queued by PUTDATA O samples sent to output device since START AO object contains channel s Index ChannelName HwChannel OutputRange UnitsRange Units 1 Mono 1 1 1 1 1 Volts You can use the Channel property to display only the channel summary information AO Channel 6 15 6 Analog Output Managing Output Data 6 16 At the core of any analog output application lies the data you want to send from a computer to an output device such as an actuator The role of the analog output subsystem is to convert digitized data to analog data for subsequent output Before you can output data to the analog output subsystem it must be queued in the engine Queuing data is managed with the putdata function In addition to this function there are several properties associated with managing output data These properties are given below Table 6 6 Analog Output Data Management Properties Property Name Description MaxSamplesQueued Indicate the maximum number of samples that can be queued in the engine RepeatOutput Specify the number of additional times queued data is output Timeout Specify an additional waiting time to queue data Queuing Data with putdata
260. g and retrieving events refer to Recording and Retrieving Event Information on page 5 48 5 35 5 Doing More with Analog Input 5 36 When Did the Trigger Occur You can find the absolute time of the first trigger event with the InitialTriggerTime property value The absolute time is returned using the MATLAB clock format year month day hour minute seconds For example the absolute time of the first trigger event for the preceding example is abstime ai InitialTriggerTime abstime 1 0e 003 1 9990 0 0040 0 0170 0 0100 0 0220 0 0041 To convert the clock vector to a more convenient form you can use the sprintf function t fix abstime sprintf d d d t 4 t 5 t 6 ans 10 22 4 You can also use the showdagevents function to return the absolute time of each trigger event For more information about trigger events refer to Recording and Retrieving Event Information on page 5 48 Device Specific Hardware Triggers Many data acquisition devices possess the ability to accept a hardware trigger Hardware triggers are processed directly by the hardware and can be either a digital signal or an analog signal Hardware triggers are often used when speed is required because a hardware device can process an input signal much faster than software The device specific hardware triggers are presented to you as additional property values Hardware triggers for Agilent Technologies Measurement Comput
261. g event device object channel and hardware information Retrieving Data and Time Information You can characterize logged data by the sample number or the time the sample was acquired To retrieve data and time information you use the syntax shown below data time abstime daqread file P1 V1 P2 V2 where e data is the retrieved data Data is returned as an m by n matrix where m is the number of samples and n is the number of channels time optional is the relative time associated with the retrieved data Time is returned as an m by 1 matrix where m is the number of samples abstime optional is the absolute time of the first trigger Absolute time is returned as a clock vector e file is the name of the log file e P1 V2 P2 V2 optional are the property name property value pairs which allow you to select the amount of data to retrieve among other things see below daqread returns data and time information in the same format as getdata If data from multiple triggers is retrieved each trigger is separated by a NaN 8 7 8 Saving and Loading the Session 8 8 You select the amount of data returned and the format of that data with the properties given below Table 8 2 daqread Properties Property Name Description Samples Specify the sample range Time Specify the relative time range Triggers Specify the trigger range Channels Specify the channel range Channel names can be
262. g hardware you should use the test feature provided by InstaCal To access this feature select the board you want to test from the PC Board List and select Analog from the Test menu For example suppose you want to verify that the analog input subsystem on your PCI DAS4020 12 board is operating correctly To do this you should connect a known signal such as that produced by a function generator to one of the channels using a BNC cable The result of such a test is shown below for channel 0 Board Test PCI DAS4020 12 at b400h x Analog Loop Back Test Advanced Scan Test ChO Avg Val 0 1995 volts 5 0 Input Ch Signal Source A D Range Eo EXTERNAL 7 V Connect a low frequency signal lt 100Hz as shown and verfiy the proper waveform CHO CS __________ EXT aie If InstaCal does not provide you with the expected results for the subsystem under test and you are sure that your test setup is configured correctly then the problem is probably with the hardware To get support for your Measurement Computing hardware visit their Web site at http www measurementcomputing com A Troubleshooting Your Hardware National Instruments Hardware If you are having trouble using the Data Acquisition Toolbox with a supported National Instruments board the reason might be that e You are using a hardware driver that is incompatible with the toolbox e Your hardware is not functioning
263. g measurements with data acquisition hardware The topics covered should help you understand the specification sheet associated with your hardware Getting Started with Describes the toolbox components and shows the Data Acquisition you how to access your hardware examine your Toolbox hardware resources and get command line help The Data Acquisition Describes all the steps you are likely to take Session when acquiring or outputting data Preface xvi Chapter Description Getting Started with Shows you how to perform basic data Analog Input acquisition tasks using your analog input subsystem Doing More with Analog Presents the complete analog input Input functionality Analog Output Shows you how to perform data acquisition Digital Input Output Saving and Loading the Session softscope The Data Acquisition Oscilloscope Function Reference Base Property Reference Device Specific Property Reference Troubleshooting Your Hardware Managing Your Memory Resources Glossary tasks using your analog output subsystem Shows you how to perform data acquisition tasks using your digital I O subsystem Shows you how to save and load device objects data and event information using several disk file formats An interactive graphical user interface GUI for streaming data into a display Presents a complete description of all toolbox functions Presents a complete description of all toolb
264. g with showdaqevents AO object 6 23 displaying with showdaqevents function AI object 5 35 I 5 Index example index 2 12 examples acquiring data NI hardware 4 18 sound card 4 14 adding lines 7 10 generating timer events DIO 7 19 logging and retrieving information AI 8 9 outputting data with a sound card 6 10 6 11 performing a linear conversion AI object 5 56 AO object 6 35 polling the data block AI 5 10 previewing and extracting data 5 14 reading and writing DIO values 7 15 retrieving event information AI object 5 50 AO object 6 30 using callback properties AI object 5 52 AO object 6 31 using putdata 6 18 voice activation AI pretriggers 5 27 repeating triggers 5 30 software trigger 5 22 execution AI object 4 12 AO object 6 8 DIO object 7 17 exporting Oscilloscope channel data 9 23 measurements 9 24 external clock 1 22 clock sources 11 24 extracting data 5 12 event information 10 61 1 6 native data 11 53 time information 5 17 F fft 4 16 FIFO 1 26 TransferMode 12 35 filtering 1 33 finding device objects 10 27 floating signal 1 23 flow of data acquired 2 4 output 2 6 flushdata 10 55 flushdata function 10 55 full duplex A 17 BitsPerSample property 12 9 function handle 5 51 functions addchannel 10 8 addline 10 13 addmuxchannel 10 16 analoginput 10 17 analogoutput 10 20 binvec2dec 10 23 clear 10 24 daqcallback 10 26 daqfind 10 27 daghelp 10 29 daqhwinfo 10 32 daqmem 10 35 da
265. gative falling edge of the digital signal is detected Gated acquisition on a TTL high level on TGIN or the 8254 gate input Note that gated acquisition mode ignores all stop trigger properties Gated acquisition on a TTL low level on TGIN This option is invalid and causes an error if the device s analog input gating is set to 8254 Gate in the DriverLINX Configuration Analog Input Subsystem panel To utilize simultaneous gated and triggered acquisition set the analog input gating to 8254 Gate in the DriverLINX Configuration Panel Analog Input subsystem and use GateHigh and HwDigital triggering through the TGIN connection pin Measurement Computing The following trigger conditions are available when TriggerType is HwDigital GateHigh GateLow TrigHigh TrigLow TrigPosEdge TrigNegEdge The trigger occurs as long as the digital signal is high The trigger occurs as long as the digital signal is low The trigger occurs when the digital signal is high The trigger occurs when the digital signal is low The trigger occurs when the positive rising edge of the digital signal is detected The trigger occurs when the negative falling edge of the digital signal is detected 11 87 TriggerCondition 11 88 The following trigger conditions are available when TriggerType is HwAnalog TrigAbove TrigBelow GateNegHys GatePosHys GateAbove GateBelow GateInWindow GateOutWindow The tri
266. ge 2 7 The device ID refers to the number associated with your board when it is installed Some vendors refer to the device ID as the device number or the board number The device ID is optional for sound cards with an ID of 0 Use the daqhwinfo function to determine the available adaptors and device IDs Each analog output object is associated with one board and one analog output subsystem For example to create an analog output object associated with a National Instruments board with device ID 1 ao analogoutput nidaq 1 The analog output object ao now exists in the MATLAB workspace You can display the class of ao with the whos command whos ao Name Size Bytes Class ao 1x1 1334 analogoutput object Grand total is 53 elements using 1334 bytes Getting Started with Analog Output Once the analog output object is created the properties listed below are automatically assigned values These general purpose properties provide descriptive information about the object based on its class type and adaptor Table 6 1 Descriptive Analog Output Properties Property Name Description Name Specify a descriptive name for the device object Type Indicate the device object type You can display the values of these properties for ao with the get function get ao Name Type ans nidaq1 A0 Analog Output Adding Channels to an Analog Output Object After creating the analog output object you must add hard
267. ged to the engine or a disk file You extract logged data from the engine with the getdata function For example to extract 500 samples for each channel contained by ai data getdata ai 500 getdata blocks the MATLAB command line until all the requested data is returned to the workspace You can extract data any time after the trigger occurs Sending Queued Data For analog output objects you must queue data in the engine with the putdata function before it can be output to the hardware For example to queue 8000 samples in the engine for each channel contained by the analog output object ao ao analogoutput winsound addchannel ao 1 2 data sin linspace 0 2 pi 500 8000 putdata ao data data Before the queued data can be output you must start the analog output object start ao When a trigger occurs the Sending property is automatically set to On and the queued data is sent to the hardware Stopping the Device Object An analog input AI or analog output AO object can stop under one of these conditions e You issue the stop function e The requested number of samples is acquired AI or sent AO e A run time hardware error occurs e A timeout occurs When the device object stops the Running Logging and Sending properties are automatically set to Of f At this point you can reconfigure the device object or immediately issue another start command using the current configuration Cleaning U
268. gers Plana Acquire Continuous gt Samples to acquire 3 r Fillthe display C Count 500 CH1 5 0Vidiv 10 0msidiv Vertical m1 3 7427 Vidiv Type independent CH1 Channel JCH0 T i r Condition Risin z f mi Valuer Scale Walue2 Tl CHO Pretrigger sec oo CHO 7 4850Vidiv 10 0msidiv r4 7 4850Vidiv Trigger 9 9 9 softscope The Data Acquisition Oscilloscope 9 10 Removing Channel Displays You can remove a channel from a display one of these ways e Channel Editor GUI The Channel pane Clear the associated check box in the first column of the Defined channels table The Channel Display pane Select lt not displayed gt from the Display column of the table e The On Off button of the Channel Scaling panel Refer to Scaling the Channel Data on page 9 11 for more information about this panel The Channel pane is shown below with the math and reference channels cleared from the Oscilloscope displays Channel Editor E x Channel Channel Properties Channel Display Define a new channel Type Math x Name Expression Oe Display faisai O Add Defined channels Name Data Source CHO Hardware channel0 M Hardware CHO Hard I Hardware CH1 Hardware channel 1 C Math m1 labs CHO abs CH1 E Reference r1 display2 Clear the math and reference channels from the Osci
269. gger occurs when the analog signal makes a transition from below the specified value to above The trigger occurs when the analog signal makes a transition from above the specified value to below The trigger occurs when the analog signal is more than the specified high value The acquisition stops if the analog signal is less than the specified low value The trigger occurs when the analog signal is less than the specified low value The acquisition stops if the analog signal is more than the specified high value The trigger occurs as long as the analog signal is more than the specified value The trigger occurs as long as the analog signal is less than the specified value The trigger occurs as long as the analog signal is within the specified range of values The trigger occurs as long as the analog signal is outside the specified range of values TriggerCondition National Instruments The following trigger condition is used when TriggerType is HwDigital None No trigger condition is required The following trigger conditions are available when TriggerType is HwAnalogChannel or HwAnalogPin AboveHighLevel The trigger occurs when the analog signal is above the specified value BelowLowLevel The trigger occurs when the analog signal is below the specified value InsideRegion The trigger occurs when the analog signal is inside the specified region LowHysteresis The trigger occurs when the analog signal is le
270. gger type with the TriggerType property The TriggerType values that are supported for all hardware are given below Table 4 4 Analog Input TriggerType Property Values TriggerType Value Description Immediate The trigger occurs just after the start function is issued Manual The trigger occurs just after you manually issue the trigger function Software The trigger occurs when the associated trigger condition is satisfied Trigger conditions are given by the TriggerCondition property Many devices have additional hardware trigger types which are available to you through the TriggerType property For example to return all the trigger types for the analog input object ai created in the preceding section set ai TriggerType Manual Immediate Software HwDigital This information tells you that the National Instruments board also supports a hardware digital trigger For a description of device specific trigger types refer to Device Specific Hardware Triggers on page 5 36 or the TriggerType reference pages in Chapter 11 Base Property Reference Note Triggering can be a complicated issue and it has many associated properties For detailed information about triggering refer to Configuring Analog Input Triggers on page 5 19 Configuring Analog Input Properties The Samples to Acquire per Trigger When a trigger executes a predefined number of samples are acquired for each channe
271. ggingMode Disk amp Memory 8 9 8 Saving and Loading the Session 8 10 4 Acquire data Start ai wait for ai to stop running and extract all the data stored in the log file as sample time pairs start ai data time daqread file00 daq Plot the data and label the figure axes subplot 211 plot data title Logging and Retrieving Data xlabel Samples ylabel Signal Volts subplot 212 plot time data xlabel Time seconds ylabel Signal Volts Make sure ai has stopped running before cleaning up the workspace waittilstop ai 2 Clean up When you no longer need ai you should remove it from memory and from the MATLAB workspace delete ai clear ai Retrieving Data Based on Samples You can retrieve data based on samples using the Samples property To retrieve samples 1000 to 2000 for both sound card channels data time daqread file00 daq Samples 1000 2000 Plot the data and label the figure axes subplot 211 plot data xlabel Samples ylabel Signal Volts subplot 212 plot time data xlabel Time seconds ylabel Signal Volts Retrieving Data Based on Channels You can retrieve data based on channels using the Channels property To retrieve samples 1000 to 2000 for the second sound card channel data time daqread file00 daq Samples 1000 2000 Channels 2 Logging Information to Disk Plot the data and label the figure axe
272. gine and in the MATLAB workspace If you create a copy of the device object it references the original device object in the engine e If IDis a numeric value then you can specify it as an integer or a string If ID contains any nonnumeric characters then you must specify it as a string see the Agilent Technologies example below e The Name property is automatically assigned a descriptive name that is produced by concatenating adaptor ID and AO You can change this name at any time analogoutput Example More About the Hardware Device Identifier When data acquisition devices are installed they are assigned a unique number which identifies the device in software The device identifier is typically assigned automatically and can usually be manually changed using a vendor supplied device configuration utility National Instruments refers to this number as the device number while Agilent Technologies refers to it is as the device ID For sound cards the device identifier is typically not exposed to you through the Microsoft Windows environment However the Data Acquisition Toolbox automatically associates each sound card with an integer ID value There are two cases to consider e If you have one sound card installed then ID is 0 You are not required to specify ID when creating an analog output object associated with this device e If you have multiple sound cards installed the first one installed has an ID of 0 the sec
273. gnal and that utilizes the maximum dynamic range of your hardware 6 34 linearly Scaling the Data Engineering Units For sound cards you might have to adjust the volume control to obtain the full scale output range of the device Refer to Sound Cards on page A 11 to learn how to access the volume control for your sound card For example suppose OutputRange is 10 10 and UnitsRange is 5 5 If a queued value is 2 5 then the scaled value is 2 5 20 10 or 5 in the appropriate units Note The data acquisition engine always clips out of range values Clipping means that an out of range value is fixed to either the minimum or maximum value that is representable by the hardware Clipping is equivalent to saturation Example Performing a Linear Conversion This example illustrates how to configure the engineering units properties for an analog output object connected to a National Instruments PCI 6024E board The queued data consists of a 4 volt peak to peak sine wave The UnitsRange property is configured so that queued data is scaled to the OutputRange property value which is fixed at 10 volts This scaling utilizes the maximum dynamic range of the analog output hardware You can run this example by typing daqdoc6_6 at the MATLAB command line 1 Create a device object Create the analog output object AO for a National Instruments board The installed adaptors and hardware IDs are found with daqhwinfo AO
274. hardware driver adaptor is to be unloaded out Captures the message returned by daqregister daqregister adaptor registers the hardware driver adaptor specified by adaptor For third party adaptors adaptor must include the full pathname daqregister adaptor unload unregisters the hardware driver adaptor specified by adaptor For third party adaptors adaptor must include the full pathname out daqregister captures the resulting message in out A hardware driver adaptor must be registered so the data acquisition engine can make use of its services Unless an adaptor is unloaded registration is required only once For adaptors that are included with the toolbox registration occurs automatically when you first create a device object However you might need to register third party adaptors manually In either case you must install the associated hardware driver before registration can occur The following command registers the sound card adaptor provided with the toolbox daqregister winsound The following command registers the third party adaptor myadaptor d11 Note that you must supply the full pathname to daqregister daqregister D MATLABR12 toolbox daq myadaptors myadaptor d1l daqreset Purpose Syntax Description See Also Remove device objects and data acquisition DLLs from memory daqreset daqreset removes all device objects existing in the engine and unloads all data acquisition
275. hat your test setup is configured correctly then the problem is probably with the hardware To get support for your National Instruments hardware visit their Web site at http www natinst com Sound Cards Sound Cards You can verify that your sound card is functioning properly by recording data and then playing back the recorded data Recording data uses the sound card s analog input subsystem while playing back data uses the sound card s analog output subsystem Successful completion of these two tasks indicates your sound card works properly The data to be recorded can come from two sources e A microphone e ACD player The first thing you should do is enable your sound card s ability to record and play data This is done using the Microsoft Windows Multimedia Properties dialog box You can access this dialog box using the Windows Start button Start gt Settings gt Control Panel gt Multimedia The Multimedia Properties dialog box for a Windows NT 4 0 platform is shown below and is configured for both playback and recording Multimedia Properties ixi Audo Video MIDI CDMusic Devices m Playback k Volume Lo f if Preferred device AudioPCI Playback fid IV Show volume control on the taskbar High Recording Volume Low High LOG A A too 1 Prefered device AudioPCI Record 7 Preferred quality co Quality z Customize I Use preferred dev
276. he device s sample rate and input type as well as the input range for each added channel The GUI shown below is configured to add both sound card channels using the default sample rate Hardware Configuration l x Adaptor winsound ID fo 7 Sample Rate Hz feooo Input Type JAC Coupled x Select the channels to add SelectAll Unselect All Hy Channel Name Description Input Range 1 7 Left Hardware channel 1 2 Right Hardware channel 2 l 11 zz OK Close Help Oscilloscope The Oscilloscope consists of these panels e Display panel The display panel contains the hardware channel data a trace and the measurements if defined The display area also contains labels for each channel s horizontal and vertical units and indicators for Each trace The trigger level if defined The location of the start of the trigger used for pretriggers e Channel panel The channel panel lists the hardware channels math channels and reference channels that are currently being viewed in a display The Channel Panel also contains knobs for configuring The display s horizontal offset and horizontal scale The selected channel s vertical offset and vertical scale 10 97 softscope 10 98 e Trigger panel The trigger panel allows you to define how data acquisition is initiated There are three trigger types One shot Acquire the specified number of samples
277. he engine automatically selects a valid sampling rate The rules governing this selection process are described in the SampleRate reference pages in Chapter 11 Base Property Reference e If the rate is outside the range of valid values then an error is returned Note For some sound cards you can set the sampling rate to any value between the minimum and maximum values defined by the hardware You can enable this feature with the StandardSampleRates property Refer to Chapter 12 Device Specific Property Reference for more information Most analog output subsystems allow simultaneous sampling of channels Therefore the maximum sampling rate for each channel is given by the maximum board rate After setting a value for SampleRate you should find out the actual rate set by the engine ActualRate get ao SampleRate Alternatively you can use the setverify function which sets a property value and returns the actual value set ActualRate setverify ao SampleRate 100000 You can find the range of valid sampling rates for your hardware with the propinfo function ValidRates propinfo ao SampleRate ValidRates ConstraintValue ans 1 0e 005 0 0000 2 0000 Getting Started with Analog Output Defining a Trigger For analog output objects a trigger is defined as an event that initiates the output of data from the engine to the analog output hardware Defining a trigger for an analog outp
278. he number of additional times the trigger executes Indicate the number of triggers that execute Specify the type of trigger to execute Except for TriggerFcn these trigger related properties are discussed in the following sections TriggerFcn is discussed in Events and Callbacks on page 5 45 Defining a Trigger Trigger Types and Conditions Defining a trigger for an analog input object involves specifying the trigger type with the TriggerType property You can think of the trigger type as the source of the trigger For some trigger types you might need to specify a trigger condition and a trigger condition value Trigger conditions are specified with the TriggerCondition property while trigger condition values are specified with the TriggerConditionValue property Configuring Analog Input Triggers The analog input TriggerType and TriggerCondition values are given below Table 5 7 Analog Input TriggerType and TriggerCondition Values TriggerType TriggerCondition Description Value Value Immediate None The trigger occurs just after you issue the start function Manual None The trigger occurs just after you manually issue the trigger function Software Rising The trigger occurs when the signal has a positive slope when passing through the specified value Falling The trigger occurs when the signal has a negative slope when passing through the specified value Leaving The trigger occurs when the signal
279. ibed below and in Chapter 11 Base Property Reference Table 5 9 Analog Input TriggerType and TriggerCondition Values for MCC Hardware TriggerType TriggerCondition Description Value Value HwDigital GateHigh The trigger occurs as long as the digital signal is high GateLow The trigger occurs as long as the digital signal is low TrigHigh The trigger occurs when the digital signal is high TrigLow The trigger occurs when the digital signal is low TrigPosEdge The trigger occurs when the positive rising edge of the digital signal is detected TrigNegEdge The trigger occurs when the negative falling edge of the digital signal is detected 5 39 5 Doing More with Analog Input 5 40 Table 5 9 Analog Input TriggerType and TriggerCondition Values for MCC Hardware Continued TriggerType TriggerCondition Description Value Value HwAnalog TrigAbove The trigger occurs when the analog signal makes a transition from below the specified value to above TrigBelow The trigger occurs when the analog signal makes a transition from above the specified value to below GateNegHys The trigger occurs when the analog signal is more than the specified high value The acquisition stops if the analog signal is less than the specified low value GatePosHys The trigger occurs when the analog signal is less than the specified low value The acquisition stops if the analog signal is more than the specified high value GateAbove
280. ices only Cancel A Troubleshooting Your Hardware A 12 You can record data and then play it back using the Windows Sound Recorder panel To access this application Start gt Programs gt Accessories gt Multimedia gt Sound Recorder The figure below shows how to record and play data 4 Sound Sound Recorder IES File Edit Effects Help Position Length 0 00 sec 0 00 sec Play button Record button You must also make sure that your microphone or CD player is enabled for recording and playback using the Windows Volume Control panel To access this application Start gt Programs gt Accessories gt Multimedia gt Volume Control The Volume Control panel is shown below The CD microphone and line devices are enabled for playback when the Mute check box is cleared for the CD Balance Microphone Balance and Line Balance volume controls respectively You can play WAV files by leaving the Mute check box cleared for the Wave Balance volume control E Volume Control BEI Options Help Volume Control CD Wave Microphone Line Balance Balance Balance Balance Balance Ce eS ae dee ees Volume Volume Volume Volume Volume T Mute all T Mute T Mute T Mute T Mute Advanced Advanced AudioPCI Mixer Sound Cards If the CD microphone or Wave Output controls do not appear in the Volume Control panel you must modify the playback properties by selecting Properties
281. ide uses p xviii Preface What Is the Data Acquisition Toolbox The Data Acquisition Toolbox is a collection of M file functions and MEX file dynamic link libraries DLLs built on the MATLAB technical computing environment The toolbox provides you with these main features e A framework for bringing live measured data into MATLAB using PC compatible plug in data acquisition hardware e Support for analog input AI analog output AO and digital I O DIO subsystems including simultaneous analog I O conversions Support for these popular hardware vendors devices Agilent Technologies E1432A 33A 34A VXI modules Keithley boards that use DriverLINX drivers Measurement Computing Corporation ComputerBoards boards National Instruments boards that use NI DAQ software except SCXI Parallel ports LPT1 LPT3 Windows sound cards Additionally you can use the Data Acquisition Toolbox Adaptor Kit to interface unsupported hardware devices to the toolbox e Event driven acquisitions Exploring the Toolbox A list of the toolbox functions is available to you by typing help daq You can view the code for any function by typing type function_name You can view the help for any function by typing daqhelp function_name You can change the way any toolbox function works by copying and renaming the M file then modifying your copy You can also extend the toolbox by adding your own M files or by using it in combination w
282. ided with this toolbox to support the functions listed below These helper functions are not documented because they are not intended for direct use Creating Device Objects Al AO DIO analoginput Create an analog input object y analogoutput Create an analog output object y digitalio Create a digital I O object y Adding Channels and Lines Al AO DIO addchannel Add hardware channels to an analog input or analog y y output object addline Add hardware lines to a digital I O object y addmuxchannel Add hardware channels when using a multiplexer board vV Getting and Setting Properties Al AO DIO get Return device object properties set Configure or display device object properties setverify Configure and return the specified property 10 3 10 Function Reference Executing the Object Al AO DIO start Start a device object V V V stop Stop a device object y y y trigger Manually execute a trigger y y waittilstop Wait for the device object to stop running y y Working with Data Al AO ODIO flushdata Remove data from the data acquisition engine getdata Extract data time and event information from the data acquisition engine getsample Immediately acquire one sample y getvalue Read values from lines V peekdata Preview most recent acquired data V putdata Queue data in the engine for eventual output putsample Immediately output one sample putvalue Write values to lines V Gett
283. ies for analog input AI and analog output AO objects are given below Property Name Description Device Objects BitsPerSample Specify the number of bits the sound card AI AO uses to represent each sample StandardSample Specify whether the valid sample rates AI AO Rates snap to a small set of standard values or if you can set the sample rate to any value within the allowed bounds Properties Alphabetical List Properties Alphabetical List This section contains detailed descriptions of all toolbox device specific properties Each property reference page contains some or all of this information e The property name e A description of the property e The property characteristics including Vendor the vendors that support the property Usage whether it is a common property or a channel or line property and which device objects the property is associated with Common properties apply to all channels or lines contained by the device object Channel line properties can be set on a per channel per line basis The device objects supported by the Data Acquisition Toolbox include analog input AI analog output AO and digital I O DIO objects Access whether the property is read write or read only Read write property values can be returned with the get command and configured with the set command Read only property values can be returned with the get command but cannot be configured wi
284. ieving Event Information 5 48 Creating and Executing Callback Functions 5 51 Examples Using Callback Properties and Functions 5 52 Linearly Scaling the Data Engineering Units 5 55 Example Performing a Linear Conversion 5 56 Analog Output 6 Getting Started with Analog Output 6 2 Creating an Analog Output Object 0 00005 6 2 Adding Channels to an Analog Output Object 6 3 Configuring Analog Output Properties 6 5 Outputting Data 1 0 eee 6 8 Analog Output Examples 0 00 eee eee eens 6 9 Evaluating the Analog Output Object Status 6 13 Managing Output Data 0 0 0 ces 6 16 Queuing Data with putdata 0 cece ees 6 16 Example Queuing Data with putdata 6 18 vi Contents Configuring Analog Output Triggers 6 20 Defining a Trigger Trigger Types 0 000 c eeu 6 21 Executing the Trigger 0 0 0 cece eens 6 22 How Many Triggers Occurred 0 000 e cece eae 6 22 When Did the Trigger Occur 0 0 0 0c cece ees 6 23 Device Specific Hardware Triggers 0 0000 e aes 6 24 Events and Callbacks 00 c eee eens 6 26 Event Types cuties haa yee Mek Ola aR ARES 6 26 Recording and Retrieving Event Information 6 28 Examples Using Callback Properties and
285. ifies a descriptive name for a hardware channel If a channel name is defined then you can reference that channel by its name If a channel name is not defined then the channel must be referenced by its index Channel names are not required to be unique You can also define descriptive channel names when channels are added to a device object with the addchannel function Usage AI AO Channel Access Read write Data type String Read only Yes when running The default value is an empty string To reference a channel by name it must contain only letters numbers and underscores and must begin with a letter Create the analog input object ai for a sound card and add two channels to it ai analoginput winsound addchannel ai 1 2 To assign a descriptive name to the first channel contained by ai Chani ai Channel 1 set Chan1 ChannelName Joe You can now reference this channel by name instead of by index set ai Joe Units Decibels Functions addchannel ChannelSkew Purpose Description Characteristics Values See Also Specify the time between consecutive scanned hardware channels Channe1Skew applies only to scanning hardware and not to simultaneous sample and hold SS H hardware If ChannelSkewMode is set to Minimum or Equisample then Channe1Skew is automatically set to the appropriate device specific read only value For SS H hardware the only valid Channe1Skew value is zero For
286. ime hardware error occurs e A timeout occurs When the device object stops the Running and Sending properties are automatically set to Off At this point you can reconfigure the device object or immediately queue more data and issue another start command using the current configuration Analog Output Examples This section illustrates how to perform basic data acquisition tasks using analog output subsystems and the Data Acquisition Toolbox For most data acquisition applications using analog output subsystems you must follow these basic steps 1 Install and connect the components of your data acquisition hardware At a minimum this involves connecting an actuator to a plug in or external data acquisition device 2 Configure your data acquisition session This involves creating a device object adding channels setting property values and using specific functions to output data Simple data acquisition applications using a sound card and a National Instruments board are given below 6 9 6 Analog Output Outputting Data with a Sound Card In this example sine wave data is generated in MATLAB output to the D A converter on the sound card and sent to a speaker The setup is shown below Data Source D A Converter Speaker MATLAB variable D A 7 You can run this example by typing daqdoc6_1 at the MATLAB command line 1
287. iment you need to perform these tasks e System setup e Calibration e Trials System Setup The first step in any data acquisition experiment is to install the hardware and software Hardware installation consists of plugging a board into your computer or installing modules into an external chassis Software installation consists of loading hardware drivers and application software onto your computer After the hardware and software are installed you can attach your sensors Calibration After the hardware and software are installed and the sensors are connected the data acquisition hardware should be calibrated Calibration consists of providing a known input to the system and recording the output For many data acquisition devices calibration can be easily accomplished with software provided by the vendor Trials After the hardware is set up and calibrated you can begin to acquire data You might think that if you completely understand the characteristics of the signal you are measuring then you should be able to configure your data acquisition system and acquire the data In the real world however your sensor might be picking up unacceptable noise levels and require shielding or you might need to run the device at a higher rate or perhaps you need to add an antialias filter to remove unwanted frequency components These real world effects act as obstacles between you and a precise accurate measurement To overcome these ob
288. in first out FIFO buffer 2 Data is transferred from the FIFO buffer to system memory using interrupts or DMA These steps happen automatically Typically all that s required from you is some initial configuration of the hardware device when it is installed The FIFO Buffer The FIFO buffer is used to temporarily store acquired data The data is temporarily stored until it can be transferred to system memory The process of transferring data into and out of an analog input FIFO buffer is given below 1 The FIFO buffer stores newly acquired samples at a constant sampling rate 2 Before the FIFO buffer is filled the software starts removing the samples For example an interrupt is generated when the FIFO is half full and signals the software to extract the samples as quickly as possible 3 Because servicing interrupts or programming the DMA controller can take up to a few milliseconds additional data is stored in the FIFO for future retrieval For a larger FIFO buffer longer latencies can be tolerated 4 The samples are transferred to system memory via the system bus for example PCI bus or AT bus After the samples are transferred the software is free to perform other tasks until the next interrupt occurs For example the data can be processed or saved to a disk file As long as the average rates of storing and extracting data are equal acquired data will not be missed and your application should run smoothly Interrupts
289. independent triggers are discussed below Immediate Trigger If TriggerType is Immediate the default value the trigger occurs immediately after the start function is issued You can configure an analog output object for continuous output by using an immediate trigger and setting RepeatOutput to inf Manual Trigger If TriggerType is Manual the trigger occurs immediately after the trigger function is issued 6 21 6 Analog Output 6 22 Executing the Trigger For an analog output trigger to occur you must follow these steps 1 Queue data in the engine 2 Configure the appropriate trigger properties 3 Issue the start function 4 Issue the trigger function if TriggerType is Manual Once the trigger occurs queued data is output to the hardware and the device object stops executing when all the queued data is output Note Only one trigger event can occur for analog output objects How Many Triggers Occurred For analog output objects only one trigger can occur You can determine if the trigger event occurred by returning the value of the TriggersExecuted property If TriggersExecuted is 0 then the trigger event did not occur If TriggersExecuted is 1 then the trigger event occurred Event information is also recorded by the EventLog property A convenient way to access event log information is with the showdaqgevents function For example suppose you create the analog output object ao for a sound card and add
290. ine for eventual output to an analog output subsystem A state of the Data Acquisition Toolbox where a device object is executing The per channel rate in samples second that an analog input or analog output subsystem converts data The process whereby an A D converter or a D A converter takes a snapshot of the data at discrete times For most applications the time interval between samples is kept constant e g sample every millisecond unless externally clocked Data acquisition hardware that samples a single input signal converts that signal to a digital value and then repeats the process for every input channel used A state of the Data Acquisition Toolbox where an analog output object is outputting sending data from the engine to the hardware A device that converts a physical variable into a signal that you can input into your data acquisition hardware The process of making a sensor signal compatible with the data acquisition hardware Signal conditioning includes amplification filtering electrical isolation and multiplexing C 5 C Glossary C 6 Single ended input SS H hardware Subsystem Trigger event Input channel configuration where there is one signal wire associated with each input signal and all input signals are connected to the same ground Single ended measurements are more susceptible to noise than differential measurements due to differences in the signal paths Data acquisitio
291. ing and National Instruments devices are discussed below and in Chapter 11 Base Property Reference Note that the available hardware trigger support depends on the board you are using Refer to your hardware documentation for detailed information about its triggering capabilities Configuring Analog Input Triggers Agilent Technologies When using Agilent Technologies hardware there are additional trigger types and trigger conditions available to you These device specific property values fall into two categories hardware digital triggering and hardware analog triggering The device specific trigger types and trigger conditions are described below and in Chapter 11 Base Property Reference Table 5 8 Analog Input TriggerType and TriggerCondition Property Values for Agilent Hardware TriggerType TriggerCondition Description Value Value HwDigital PositiveEdge The trigger occurs when the positive rising edge of a digital signal is detected NegativeEdge The trigger occurs when the negative falling edge of a digital signal is detected HwAnalog Rising The trigger occurs when the analog signal has a positive slope when passing through the specified range of values Falling The trigger occurs when the analog signal has a negative slope when passing through the specified range of values Leaving The trigger occurs when the analog signal leaves the specified range of values Entering The trigger occurs wh
292. ing Information and Help Al AO DIO daqhelp Display help for device objects constructors adaptors y y y functions and properties daqhwinfo Display data acquisition hardware information V V V 10 4 Functions By Category Getting Information and Help Continued Al AO DIO daqpropedit Invoke the property editor graphical user interface y propinfo Return property characteristics for device objects y channels or lines General Purpose Al AO DIO binvec2dec Convert binary vector to decimal value y clear Remove device objects from the MATLAB workspace daqcallback A callback function that displays event information for the specified event daqfind Return device objects channels or lines from the data y y y acquisition engine to the MATLAB workspace daqmem Allocate or display memory resources y V daqread Read a Data Acquisition Toolbox daq file y daqschool Interface for displaying toolbox tutorials y y y daqregister Register or unregister a hardware driver adaptor y daqreset Remove device objects and data acquisition DLLs from y memory dec2binvec Convert decimal value to binary vector delete Remove device objects channels or lines from the data V y acquisition engine disp Display summary information for device objects y V V channels or lines ischannel Check for channels V v V isdioline Check for lines V N v 10 5 10 Function Reference 10 6 General Purpose Continued Al AO DI
293. ingleEnded or NonReferencedSingleEnded Channels configured for differential input are not connected to a fixed reference such as earth and input signals are measured as the difference between two terminals Channels configured for single ended input are connected to a common ground and input signals are measured with respect to this ground Channels configured for nonreferenced single ended input are connected to their own ground reference and input signals are measured with respect to this reference The ground reference is tied to the negative input of the instrumentation amplifier The number of channels that you can add to a device object depends on the InputType property value Most National Instruments boards have 16 or 64 single ended inputs and 8 or 32 differential inputs which are interleaved in banks of 8 This means that for a 64 channel board with single ended inputs you can add all 64 channels However if the channels are configured for differential input you can only add channels 0 7 16 23 32 39 and 48 55 Sound Cards For sound cards the only valid InputType value is AC Coupled When input channels are AC coupled they are connected so that constant DC signal levels are suppressed and only nonzero AC signals are measured Configuring and Sampling Input Channels Sampling Rate The sampling rate is defined as the per channel rate in samples second that an analog input subsystem converts analog data to digital data
294. ion StopTriggerConditionValue StopTriggerDelay StopTriggerDelayUnits StopTriggerType 12 27 StopTriggerCondition Purpose Description Characteristics Values 12 28 Specify the condition that must be satisfied before a stop trigger executes StopTriggerCondition can be None Rising or Falling As described below the stop trigger condition depends on the value specified for the StopTriggerType property which can be HwDigital or HwAnalog If StopTriggerCondition is Rising the trigger executes on the rising edge of TGIN line HwDigital or when the analog input signal rises above the value given in StopTriggerConditionValue HwAnalog If StopTriggerConditionis Falling the trigger executes on the falling edge of TGIN line HwDigital or when the analog input signal falls below the value given in StopTriggerConditionValue HwAnalog If you use stop triggers in conjunction with start triggers and both trigger types are HwDigital then the trigger conditions must be the same for both triggers for example both Rising or both Falling Vendor Keithley Usage AI Common Access Read write Data Type String Read only Yes when running The following stop trigger condition is used when StopTriggerType is None None No stop trigger condition is required StopTriggerCondition The following stop trigger conditions are used when StopTriggerType is HwDigital or HwAnalog Rising Trigger on the rising edge of T
295. ionally pretrigger data has negative time associated with it because time 0 corresponds to the time the trigger event occurs and data logging is initiated Voice Activation with Pretriggering 0 3 T T T 0 27 4 Loew tae thay Signal Level Volts 4 i i 0 015 0 01 0 005 0 0 005 0 01 0 015 Time sec Repeating Triggers You can configure triggers to occur once one shot acquisition or multiple times You control trigger repeats with the TriggerRepeat property If TriggerRepeat is set to its default value of 0 then the trigger occurs once If TriggerRepeat is set to a positive integer value then the trigger is repeated the specified number of times If TriggerRepeat is set to inf then the trigger repeats continuously and you can stop the device object only by issuing the stop function 5 29 5 Doing More with Analog Input 5 30 Example Voice Activation and Repeating Triggers This example modifies daqdoc5 3 such that two triggers are issued The specified amount of data is acquired for each trigger and stored in separate variables The Timeout value is set to five seconds Therefore if getdata does not return the specified number of samples in the time given by the TimeOut property plus the time required to acquire the data the acquisition will be aborted You can run this example by typing daqdoc5_5 at the MATLAB command line 1 Create a device object Create the analog input obj
296. ions Indianapolis Indiana 1997 The Measurement Instrumentation and Sensors Handbook edited by John G Webster CRC Press Boca Raton FL 1999 PCI MIO E Series User Manual January 1997 Edition Part Number 320945B 01 National Instruments Austin TX 1997 Getting Started with the Data Acquisition Toolbox This chapter provides the information you need to get started with the Data Acquisition Toolbox The sections are as follows Toolbox Components p 2 2 Accessing Your Hardware p 2 8 Understanding the Toolbox Capabilities p 2 12 Examining Your Hardware Resources p 2 17 Getting Help p 2 20 The M files and hardware driver adaptors that compose the toolbox Examples that show you how to acquire data output data and read and write digital values Resources to help you understand the toolbox capabilities including demos and documentation examples Return hardware related information visible to the toolbox including the installed adaptors and the syntax for creating device objects Get help using the Help browser M file help and other methods 2 Getting Started with the Data Acquisition Toolbox Toolbox Components The Data Acquisition Toolbox consists of three distinct components M file functions the data acquisition engine and hardware driver adaptors As shown below these components allow you to pass information between MATLAB and your data acquisition hardware MATLAB
297. is Off data is not being output to the analog output subsystem although you can output a single sample with the putsample function Characteristics Usage Access Data type Read only when running Values Off On See Also Functions putsample Properties Running 11 74 AO Common Read only String N A Data is not being sent to the analog output hardware Data is being sent to the analog output hardware SensorRange Purpose Description Characteristics Values See Also Specify the range of data you expect from your sensor You use SensorRange to scale your data to reflect the range you expect from your sensor You can find the appropriate sensor range from your sensor s specification sheet For example an accelerometer might have a sensor range of 5 volts which corresponds to 50 g s 1 g 9 80 m s s The data is scaled while it is extracted from the engine with the getdata function according to the formula scaled value A D value units range sensor range The A D value is constrained by the InputRange property which reflects the gain and polarity of your hardware channels The units range is given by the UnitsRange property Usage AI Channel Access Read write Data type Two element vector of doubles Read only No when running The default value is determined by the default value of the InputRange property Functions getdata Properties InputRange Units UnitsRange
298. is attached to the channel then the grounding mode is automatically set to the appropriate value If a dumb break out box or no break out box is attached to the channel the grounding mode is given by the GroundingMode value In this case no hardware settings are changed and no errors are generated Vendor Usage Access Data type Read only when running Grounded Floating Agilent Technologies AI Channel Read write String Yes The input channel is grounded The input channel is floating 12 13 InputMode Purpose Description Characteristics 12 14 Specify the channel input mode InputMode can be set to Voltage ICP Charge Mic or 200VoltMic You can set InputMode to Charge only if a charge break out box is attached to the specified channel Your can set InputMode to Mic or 200Vo1tMic only if a microphone break out box is attached to the specified channel For each input mode the full scale setting is configured with the InputRange property There is no ICP current source inside the E1482 device Instead you can attach a break out box containing an ICP current source to the input When this ICP break out box is attached setting InputMode to ICP enables the ICP current source in the break out box If there is no ICP break out box attached to the input then setting InputMode to ICP does nothing Note Ifa channel is not connected to a smart break out box then changing its input mode causes the in
299. is converted into an analog signal and output to an actuator For example a vector of data in MATLAB is converted to an analog signal by a sound card and output to a loudspeaker Data Acquisition Hardware Data acquisition hardware is either internal and installed directly into an expansion slot inside your computer or external and connected to your computer through an external cable For example VXI modules are installed in an external VXI chassis and data is transferred between MATLAB and the module using an external link such as FireWire IEEE 1394 At the simplest level data acquisition hardware is characterized by the subsystems it possesses A subsystem is a component of your data acquisition hardware that performs a specialized task Common subsystems include e Analog input e Analog output e Digital input output Counter timer Hardware devices that consist of multiple subsystems such as the one depicted below are called multifunction boards Analoginput Analog output subsystem subsystem Digital I O Counter timer subsystem subsystem 1 5 T introduction to Data Acquisition 1 6 Analog Input Subsystems Analog input subsystems convert real world analog input signals from a sensor into bits that can be read by your computer Perhaps the most important of all the subsystems commonly available they are typically multichannel devices offering 12
300. issued Trigger Start the hardware after the trigger function is issued Create the analog input object ai and the analog output object ao for a sound card and add two channels to each device object ai analoginput winsound addchannel ai 1 2 ao analogoutput winsound addchannel ao 1 2 11 49 ManualTriggerHwOn See Also 11 50 To operate the sound card in full duplex mode and to minimize the time between when ai starts and ao starts you configure ManualTriggerHwOn to Trigger for ai and TriggerType to Manual for both ai and ao set ai ao TriggerType Manual ai ManualTriggerHwOn Trigger The analog input and analog output hardware devices will both start after you issue the trigger function For a detailed example that uses ManualTriggerHwon refer to Starting Multiple Device Objects on page 6 37 Functions peekdata start trigger Properties TriggerType MaxSamplesQueuved Purpose Indicate the maximum number of samples that can be queued in the engine Description MaxSamplesQueued indicates the maximum number of samples allowed in the analog output queue The default value is calculated by the engine and is based on the memory resources of your system You can override the default value of MaxSamplesQueued with the daqmem function The value of MaxSamplesQueued can affect the behavior of putdata For example if the queued data exceeds the value of MaxSamplesQueued then putd
301. ith other products such as the Signal Processing Toolbox or the Instrument Control Toolbox xii Related Products Related Products The MathWorks provides several related products that are especially relevant to the kinds of tasks you can perform with the Data Acquisition Toolbox For more information about any of these products see either e The online documentation for that product if it is installed or if you are reading the documentation from the CD e The MathWorks Web site at http www mathworks com see the products section The toolboxes listed below all include functions that extend the capabilities of MATLAB Product Description Control System Toolbox Database Toolbox Instrument Control Toolbox MATLAB Report Generator Neural Network Toolbox Signal Processing Toolbox Statistics Toolbox System Identification Toolbox Wavelet Toolbox Design and analyze feedback control systems Exchange data with relational databases Control and communicate with test and measurement instruments Automatically generate documentation for MATLAB applications and data Design and simulate neural networks Perform signal processing analysis and algorithm development Apply statistical algorithms and probability models Create linear dynamic models from measured input output data Analyze compress and denoise signals and images using wavelet techniques xiii Preface Using
302. j Line returns the length of the line group contained by obj Create the analog input object ai for a National Instruments board and add eight channels to it ai analoginput nidaq 1 aich addchannel ai 0 7 Create the analog output object ao for a National Instruments board add one channel to it and create the device object array aiao ao analogoutput nidaq 1 aoch addchannel ao 0 aiao ai ao Index Subsystem Name 1 Analog Input nidaqi AI 2 Analog Output nidaq1 A0 10 69 length See Also 10 70 To find the length of aiao length aiao ans 2 To find the length of the analog input channel group length aich ans 8 Functions size load Purpose Syntax Arguments Description Remarks Load device objects channels or lines into the MATLAB workspace load file load file obji obj2 out load file obj1 obj2 file The MAT file name obj1 obj2 Device objects an array of device objects channels or lines out A structure containing the loaded device objects load file returns all variables from the MAT file file into the MATLAB workspace load file obj1 obj2 returns the specified device objects from the MAT file file into the MATLAB workspace out load file obji obj2 returns the specified device objects from the MAT file file as a structure to out instead of directly loading them into the workspace The field names in out m
303. ject 6 21 Oscilloscope 9 14 TriggersExecuted property 11 94 TriggerType property 11 95 Type property 11 98 U undersampling 1 34 Units property 11 99 UnitsRange property 11 100 Universal Library driver A 5 UserData property 11 101 saving values to a MAT file 8 2 V verifying property values 4 9 voice activation example 5 22 W waittilstop function 10 108 Workspace browser DAQ Help 2 20 Display Hardware Info 2 19 Display Summary 4 22 Property Editor 3 20 Show DAQ Events AI object 5 50 AO object 6 30 writing digital values 7 12 Index I 16
304. ject is valid isvalid ai ans 1 10 67 isvalid See Also 10 68 To verify the channels are valid isvalid ch ans 1 1 1 1 1 1 1 1 If you delete a channel then isvalid returns a logical 0 in the appropriate location delete ai Channel 3 isvalid ch ans 1 1 0 1 1 1 1 1 Typically you use isvalid directly only when you are creating your own M files Suppose you create the function myfunc for use with the Data Acquisition Toolbox If myfunc is passed the previously defined device object ai as an input argument myfunc ai the first thing you should do in the function is check if ai is a valid device object function myfunc obj Determine if an invalid handle was passed if isvalid obj error Invalid data acquisition object passed end You can examine the Data Acquisition Toolbox M files for examples that use isvalid Functions clear delete ischannel isdioline length Purpose Syntax Arguments Description Example Return the length of a device object channel group or line group out length obj out length obj Channe1l out length obj Line obj A device object or array of device objects obj Channel The channels contained by obj obj Line The lines contained by obj out A double out length obj returns the length of the device object obj to out out length obj Channel returns the length of the channel group contained by obj out length ob
305. k AvailPageFile Indicates the number of bytes available in the paging file TotalVirtual Indicates the total number of bytes that can be described in the user mode portion of the virtual address space of the calling process 10 35 daqmem Remarks Example 10 36 Field Description AvailVirtual Indicates the number of bytes of unreserved and uncommitted memory in the user mode portion of the virtual address space of the calling process UsedDaq The total memory used by all device objects Note that all the above fields except for UsedDaq are identical to the fields returned by Windows MemoryStatus function out daqmem obj returns a 1 by N structure out containing two fields UsedBytes and MaxBytes for the device object obj N is the number of device objects specified by obj UsedBytes returns the number of bytes used by obj MaxBytes returns the maximum number of bytes that can be used by obj daqmem obj maxmem sets the maximum memory that can be allocated for obj to the value specified by maxmem More About Allocating and Displaying Memory Resources e For analog output objects daqmem obj maxmem controls the value of the MaxSamplesQueued property e If you manually configure the BufferingConfig property then this value supersedes the values specified by daqmem obj maxmem and the MaxSamplesQueued property Create the analog input object aiwin for a sound card and the analog input object
306. l group member and logged to the engine or a disk file You specify the number of samples to acquire per trigger with the SamplesPerTrigger property The default value of SamplesPerTrigger is calculated by the engine such that 1 second of data is collected and is based on the default value of SampleRate In general to calculate the acquisition time for each trigger you apply the formula acquisition time seconds samples per trigger sampling rate in Hz For example to acquire 5 seconds of data per trigger for each channel contained by ai set ai SamplesPerTrigger 500000 To continually acquire data you set SamplesPerTrigger to inf set ai SamplesPerTrigger inf A continuous acquisition stops only if you issue the stop function or an error occurs 4 Getting Started with Analog Input Acquiring Data After you configure the analog input object you can acquire data Acquiring data involves these three steps 1 Starting the analog input object 2 Logging data 3 Stopping the analog input object Starting the Analog Input Object You start an analog input object with the start function For example to start the analog input object ai ai analoginput winsound addchannel ai 1 2 start ai After start is issued the Running property is automatically set to On and both the device object and hardware device execute according to the configured and default property values While you are acquiring data
307. l the sampling rate define the trigger type and define the samples to be acquired per trigger Analog input properties related to the basic setup are given below Table 4 3 Analog Input Basic Setup Properties Property Name Description SampleRate Specify the per channel rate at which analog data is converted to digital data SamplesPerTrigger Specify the number of samples to acquire for each channel group member for each trigger that occurs TriggerType Specify the type of trigger to execute The Sampling Rate You control the rate at which an analog input subsystem converts analog data to digital data with the SampleRate property SampleRate must be specified as samples per second For example to set the sampling rate for each channel of your National Instruments board to 100 000 samples per second 100 kHz ai analoginput nidaq 1 addchannel ai 0 1 set ai SampleRate 100000 Configuring Analog Input Properties Data acquisition boards typically have predefined sampling rates that you can set If you specify a sampling rate that does not match one of these predefined values there are two possibilities e If the rate is within the range of valid values then the engine automatically selects a valid sampling rate The rules governing this selection process are described in the SampleRate reference pages in Chapter 11 Base Property Reference e If the rate is outside the range of valid values the
308. lay data make sure that the sound card and input devices are enabled for recording and playback as described in the beginning of this section Testing with a CD Player To test your sound card with a CD player follow these steps Check that your CD is physically connected to your sound card Open your computer and locate the back of the CD player If there is a wire connecting the Audio Out CD port with the sound card you can record audio data from your CD If there is no wire connecting your CD and sound card you must either make this connection or use the microphone to record data A Troubleshooting Your Hardware A 16 2 Put an audio CD into your CD player The Windows CD Player application should be automatically invoked and begin playing the CD If this doesn t occur then you must access the application manually Start gt Programs gt Accessories gt Multimedia gt CD Player The figure below shows how to play a CD with the CD Player application amp CD Player Mm Ei Disc View Options Help BOOS To El Play button Title The Sun Years Track Folsom Prison Blues lt 0 3 While the CD is playing record audio data by selecting the Record button on the Sound Recorder While recording the green line in the Sound Recorder should indicate that data is being captured If this is the case then the analog input subsystem on your sound card is functioning properly Note that the CD player convert
309. lback function daqdoc6_4disp not shown below displays the number of events that were output from the engine whenever the samples output event occurred 1 Create a device object Create the analog output object AO for a sound card The installed adaptors and hardware IDs are found with daqhwinfo AO analogoutput winsound A analogoutput nidaq 1 A analogoutput mcc 1 oe 0 0 2 Add channels Add two channels to AO chans addchannel A0 1 2 chans addchannel A0 0 1 For NI and MCC 3 Configure property values Configure the trigger to repeat four times specify daqdoc6_4disp as the M file callback function to execute whenever 8000 samples are output generate data to be queued and queue the data with one call to putdata set AO SampleRate 8000 ActualRate get AO SampleRate set AO RepeatOutput 4 set AO SamplesOutputFcnCount 8000 freq get AO SamplesOutputFcnCount set AO SamplesOutputFcen daqdoc6 4disp data sin linspace 0 2 pi 500 3 freq putdata AO data data 6 31 6 Analog Output 6 32 4 Output data Start AO The waittilstop function blocks the MATLAB command line and waits for AO to stop running start AO waittilstop A0 20 5 Clean up When you no longer need AO you should remove it from memory and from the MATLAB workspace delete A0O clear AO Displaying EventLog Information This example illustrates how callb
310. leaves the specified range of values Entering The trigger occurs when the signal enters the specified range of values For some devices additional trigger types and trigger conditions are available Refer to the TriggerType and TriggerCondition reference pages in Chapter 11 Base Property Reference for these device specific values Trigger types are grouped into two main categories e Device independent triggers e Device specific hardware triggers The trigger types shown above are device independent triggers because they are available for all supported hardware For these trigger types the callback that initiates the trigger event involves satisfying a trigger condition in the engine software trigger type or issuing a toolbox function start or trigger Conversely device specific hardware triggers depend on the specific hardware 5 21 5 Doing More with Analog Input 5 22 device you are using For these trigger types the callback that initiates the trigger event involves an external analog or digital signal Device specific hardware triggers for National Instruments Measurement Computing and Agilent Technologies devices are discussed in Device Specific Hardware Triggers on page 5 36 Device independent triggers are discussed below Immediate Trigger If TriggerType is Immediate the default value the trigger occurs immediately after the start function is issued You can configure an analog input obje
311. line and port characteristics with the daqhwinfo function For example National Instruments AT MIO 16DE 10 board has four ports with eight lines per port To return the digital I O characteristics for this board hwinfo daghwinfo dio Display the line characteristics for each port hwinfo Port 1 ans ID 0 LineIDs 0 123 45 6 7 Direction in out Config line hwinfo Port 2 ans ID 2 LineIDs 0123 45 6 7 Direction in out Config port Adding Lines to a Digital I O Object hwinfo Port 3 ans ID 3 LineIDs 0123 45 6 7 Direction in out Config port hwinfo Port 4 ans ID 4 LineIDs 01234567 Direction in out Config port This information tells you that you can configure all 32 lines for either input or output and that the first port is line configurable while the remaining ports are port configurable Parallel Port Characteristics The parallel port consists of eight data lines four control lines five status lines and eight ground lines In normal usage the lines are controlled by the host computer software and the peripheral device following a protocol such as IEEE Standard 1284 1994 The protocol defines procedures for transferring data such as handshaking returning status information and so on However the toolbox uses the parallel port as a basic digital I O device and no protocol is needed Therefore you can use the port to input and output digi
312. ling SamplesAcquired The drawnow command forces MATLAB to update the plot Because peekdata is used all acquired data might not be displayed start AI i 1 while AI SamplesAcquired lt AI SamplesPerTrigger while AI SamplesAcquired lt 1000 i end data peekdata AI 1000 set P ydata data set T String sprintf Peekdata calls num2str i drawnow i i 1 end Make sure AI has stopped running before cleaning up the workspace waittilstop AI 2 5 Clean up When you no longer need AI you should remove it from memory and from the MATLAB workspace delete AI clear AI As you run this example you might not preview all 80 000 samples stored in the engine This is because the engine might store data faster than it can be displayed and peekdata does not guarantee that all requested samples are processed 5 Doing More with Analog Input Extracting Data from the Engine Many data acquisition applications require that data is acquired at a fixed often high rate and that the data is processed in some way immediately after it is collected For example you might want to perform an FFT on the acquired data and then save it to disk When processing data you must extract it from the engine If acquired data is not extracted in a timely fashion it can be overwritten Data is extracted from the engine with the getdata function For example to extract 1000 samples for the analog input object ai data getdata ai 1
313. llback function to be executed for any event by specifying it as the value for the associated callback property For analog input objects daqcallback is the default value for the DataMissedFcn and RuntimeErrorFcn properties For analog output objects daqcallback is the default value for the RuntimeErrorFcn property You can use the showdagevents function to easily display event information captured by the EventLog property Create the analog input object ai and call daqcallback when a trigger event occurs ai analoginput winsound addchannel ai 1 set ai TriggerRepeat 3 set ai TriggerFcn daqcallback start ai Functions showdaqgevents Properties DataMissedFcn EventLog RuntimeErrorFcn daaqfind Purpose Syntax Arguments Description Return device objects channels or lines from the data acquisition engine to the MATLAB workspace out daqfind out daqfind PropertyName PropertyValue out daqfind S out daqfind obj PropertyName PropertyValue PropertyName A device object channel or line property name PropertyValue A device object channel or line property value obj A device object array of device objects channels or lines S A structure with field names that are property names and field values that are property values out An array or cell array of device objects channels or lines out daqfind returns all device objects that exist in the data acquisi
314. lloscope Note that if you clear the check boxes then in addition to the channels not being displayed e For hardware channels data is not streamed into the Oscilloscope e For math and reference channels the values are not calculated Scaling the Channel Data Scaling the Channel Data You can scale the defined channels using the Channel Scaling panel In particular you can modify e The horizontal scaling and offset for all display components e The vertical scaling and offset for one or more channels To simultaneously modify the vertical scaling for multiple channels select the desired channel names in the list box Additionally using the On Off button you can add or remove the selected traces from the Oscilloscope As shown below the horizontal scale is changed to approximately 5 ms div and the vertical scale is modified to maximize the trace amplitudes Note that the horizontal and vertical scaling information is shown at the bottom of each display component Oscilloscope File Edit Help Channel Scaling Horizontal CH1 otes Sealg Turn this Scale knob until fi i the displays accommodate about 50 ms of data Vertical ooo CH1 1 7188Vidiv 0037msidiv m CH1 E A Offset Scale Turn this Seale knob until cle P the trace amplitudes are maximized in each display CHO 2 57 30Vidiv 5 0037 msidiv On To specify a precise horizontal scale or offset you modif
315. lly selected by the driver based on the board type and the sampling rate If TransferMode is InterruptPerPoint a single conversion is transferred for each interrupt You should use this property value if your sampling rate is less the 5 kHz or you specify a small block size for memory buffering as defined by the BufferingConfig property If TransferMode is DMA data is transferred using a single DMA channel If TransferMode is InterruptPerBlock a block of data is transferred for each interrupt You should use this property value if your sampling rate is greater than 5 kHz and you are using a board that has a fast maximum sampling rate Note that a data block is defined by the board and usually corresponds to half the FIFO size For Keithley hardware TransferMode can be Interrupts or DMA If TransferMode is Interrupts then data is transferred from the hardware first in first out memory buffer FIFO to system memory using interrupts If TransferMode is DMA then data is transferred from the hardware FIFO buffer to system memory using a single DMA channel Note that if bus mastering is disabled in the DriverLINX Configuration panel for the device then DMA is not offered as an option 12 35 TransferMode Characteristics Values 12 36 Note If your sampling rate is greater than around 5 kHz you should avoid using interrupts if possible The recommended TransferMode setting for your application will be described in your hardware
316. lowing categories based on usage Analog Input Basic Setup Properties SamplesPer Specify the number of samples to acquire for each Trigger channel group member for each trigger that occurs SampleRate Specify the per channel rate at which analog data is converted to digital data TriggerType Specify the type of trigger to execute 11 bs Property Referenc Analog Input Logging Properties LogFileName Logging LoggingMode LogToDiskMode Specify the name of the disk file to which information is logged Indicate if data is being logged to memory or to a disk file Specify the destination for acquired data Specify whether data events and hardware information are saved to one disk file or to multiple disk files Analog Input Trigger Properties InitialTrigger Time ManualTrigger HwOn TriggerFecn TriggerChannel TriggerCondition TriggerCondition Value TriggerDelay TriggerDelay Units Indicate the absolute time of the first trigger Specify that the hardware device starts when a manual trigger is issued Specify the M file callback function to execute when a trigger occurs Specify the channels serving as trigger sources Specify the condition that must be satisfied before a trigger executes Specify one or more voltage values that must be satisfied before a trigger executes Specify the delay value for data logging Specify the units in which trigger del
317. ls or lines are added to the device object Create the analog input object ai for a National Instruments board and add three hardware channels to it ai analoginput nidaq 1 chans addchannel ai 0 2 To return the parent for channel 2 parent ai Channel 2 Parent parent is an exact copy of ai isequal ai parent ans 1 Port Purpose Description Characteristics Values Example See Also Specify the port ID Hardware lines are often grouped together as a port Digital I O subsystems can consist of multiple ports and typically have eight lines per port When adding hardware lines to a digital I O object with addline you can specify the port ID The port ID is stored in the Port property If the port ID is not specified then the smallest port ID value is automatically used Usage DIO Line Access Read only Data type Double Read only N A when running The port ID is defined when line are added to the digital I O object with addline Create the digital I O object dio and add two hardware channels to it dio digitalio nidaq 1 addline dio 0 1 In You can use Port property to return the port IDs associated with the lines contained by dio dio Line Port ans 0 0 Functions addline 11 59 RepeatOutput Purpose Description Characteristics Values Example See Also 11 60 Specify the number of additional times queued data is output To send data to a
318. lue from all lines contained by obj as a binary vector to out out getvalue obj Line index returns the current value from the lines specified by obj Line index More About Reading Values from Lines e By default out is returned as a binary vector binvec A binvec value is constructed with the least significant bit LSB in the first column and the most significant bit MSB in the last column For example the decimal number 23 is written as the binvec value 1110 1 e You can convert a binvec value to a decimal value with the binvec2dec function e If obj contains lines from a port configurable device the data acquisition engine will automatically read from all the lines even if they are not contained by the device object Create the digital I O object dio and add eight input lines to it dio digitalio nidaq 1 lines addline dio 0 7 in To return the current values from all lines contained by dio as a binvec value out getvalue dio Functions binvec2dec ischannel Purpose Syntax Arguments Description Remarks Example See Also Check for channels out ischannel obj Channel index obj Channel index One or more channels contained by obj out A logical value out ischannel obj Channel index returns a logical 1 to out if obj Channel index is a channel Otherwise a logical 0 is returned ischannel does not determine if channels are valid associated with hardware To
319. mance might be adversely affected If you do not have this requirement you might want to use the TimerFcn property Start Event A start event is generated immediately after the start function is issued This event executes the callback function specified for StartFon When the StartFcn M file has finished executing Running is automatically set to On and the device object and hardware device begin executing The device object is not started if an error occurs while executing the callback function Stop Event A stop event is generated immediately after the device object and hardware device stop running This occurs when e The stop function is issued e The requested number of samples is acquired e A run time error occurs A stop event executes the callback function specified for StopFcen Under most circumstances the callback function is not guaranteed to complete execution until sometime after the device object and hardware device stop running and the Running property is set to Off Timer Event A timer event is generated whenever the time specified by the TimerPeriod property passes This event executes the callback function specified for TimerFcn Time is measured relative to when the device object starts running Some timer events might not be processed if your system is significantly slowed or ifthe TimerPeriod value is too small For example a common application for timer events is to display data However because displaying da
320. mation to a disk file e Acquired data e Event information e Device object and channel information e Hardware information Logging information to disk provides a permanent record of your data acquisition session and is an easy way to debug your application As shown below you can think of the logged information as a stream of data and events Start Trigger 1 Trigger 2 Trigger n Stop Time P Data logged to file The properties associated with logging information to a disk file are given below Table 8 1 Analog Input Logging Properties Property Name Description LogFileName Specify the name of the disk file to which information is logged Logging Indicate if data is being logged 8 Saving and Loading the Session 8 6 Table 8 1 Analog Input Logging Properties Continued Property Name Description LoggingMode Specify the destination for acquired data LogToDiskMode Specify whether data device object information and hardware information is saved to one disk file or to multiple disk files You can initiate logging by setting LoggingMode to Disk or Disk amp Memory A new log file is created each time you issue the start function and each different analog input object must log information to a separate log file Writing to disk is performed as soon as possible after the current data block is filled You can choose whether a log file is overwritten or if multiple log files are creat
321. mory access DMA or interrupts DMA is hardware controlled and therefore extremely fast Interrupts might be slow because of the latency time between when a board requests interrupt servicing and when the computer responds The maximum acquisition rate is also determined by the computer s bus architecture Refer to How Are Acquired Samples Clocked on page 1 22 for more information about DMA and interrupts Software Regardless of the hardware you are using you must send information to the hardware and receive information from the hardware You send configuration information to the hardware such as the sampling rate and receive information from the hardware such as data status messages and error messages You might also need to supply the hardware with information so that you can integrate it with other hardware and with computer resources This information exchange is accomplished with software The Data Acquisition System There are two kinds of software e Driver software e Application software For example suppose you are using the Data Acquisition Toolbox with a National Instruments AT MIO 16E 1 board and its associated NI DAQ driver The relationship between you the driver software the application software and the hardware is shown below User Application software Driver software d Hardware
322. mple uses a National Instruments PCI 6024E board If you are using a different supported hardware device you should modify the adaptor name and the device ID supplied to the creation function as needed If you want detailed information about any functions that are used refer to Chapter 10 Function Reference If you want detailed information about any properties that are used refer to Chapter 11 Base Property Reference Acquiring Data If you have a sound card installed you can run the following example which acquires one second of data from two analog input hardware channels and then plots the acquired data You should modify this example to suit your specific application needs If you want detailed information about acquiring data refer to Chapter 5 Doing More with Analog Input 1 Create a device object Create the analog input object ai for a sound card ai analoginput winsound 2 Add channels Add two hardware channels to ai addchannel ai 1 2 Accessing Your Hardware 3 Configure property values Configure the sampling rate to 44 1 kHz and collect 1 second of data 44 100 samples for each channel set ai SampleRate 44100 set ai SamplesPerTrigger 44100 4 Acquire data Start the acquisition When all the data is acquired ai automatically stops executing start ai data getdata ai plot data 5 Clean up When you no longer need ai you should remove it f
323. mplete listing of the device object s functions and properties is displayed along with a brief description of each function and property The constructor help is also displayed e You can display object specific function information by specifying name as object function For example to display the help for an analog input object s getdata function name is analoginput getdata e You can display object specific property information by specifying name as obj property For example to display the help for an analog input object s SampleRate property name is analoginput SampleRate daghelp Example See Also For the daqhelp obj name syntax e If name is the name of a device object constructor and the m extension is included the constructor help is displayed e If name is the name of a function or property the function or property help is displayed The following commands are some of the ways you can use daghelp to obtain help on device objects constructors adaptors functions and properties daqhelp analogoutput out daghelp analogoutput m daqhelp set daqhelp analoginput peekdata daqhelp analoginput TriggerDelayUnits The following commands are some of the ways you can use daghelp to obtain information about functions and properties for an existing device object ai analoginput winsound daqhelp ai InitialTriggerTime out daghelp ai getsample Functions propinfo 10 31 da
324. multiple triggers are included in a single getdata call a NaN is inserted into the returned data and time arrays and the absolute time returned is given by the first trigger e MATLAB supports math operations only for the double data type Therefore to use math functions on native data you must convert it to doubles Create the analog input object ai for a National Instruments board and add hardware channels 0 3 to it ai analoginput nidaq 1 addchannel ai 0 3 Configure a one second acquisition with SampleRate set to 1000 samples per second and SamplesPerTrigger set to 1000 samples per trigger set ai SampleRate 1000 set ai SamplesPerTrigger 1000 start ai The following getdata command blocks execution control until all sample time pairs the absolute time of the trigger and any events that occurred during the getdata call are returned data time abstime events getdata ai data is returned as a 1000 by 4 array of doubles time is returned as a 1000 by 1 vector of relative times abstime is returned as a clock vector and events is returned as a 3 by 1 structure array 10 61 getdata See Also 10 62 The three events returned are the start event the trigger event and the stop event To return specific event information about the stop event you must access the Type and Data fields EventType events 3 Type EventData events 3 Data Functions flushdata getsample peekdata Prop
325. must match the characteristics of the physical variable you are measuring with the characteristics of the sensor The two most important sensor characteristics are e The sensor output e The sensor bandwidth Sensor Output The output from a sensor can be an analog signal or a digital signal and the output variable is usually a voltage although some sensors output current Current Signals Current is often used to transmit signals in noisy environments because it is much less affected by environmental noise The full scale range of the current signal is often either 4 20 mA or 0 20 mA A 4 20 mA signal has the advantage that even at minimum signal value there should be a detectable current flowing The absence of this indicates a wiring problem Before conversion by the analog input subsystem the current signals are usually turned into voltage signals by a current sensing resistor The resistor should be of high precision perhaps 0 03 or 0 01 depending on the resolution of your hardware Additionally the voltage signal should match the signal to an input range of the analog input hardware For 4 20 mA signals a 50 ohm resistor will give a voltage of 1 V for a 20 mA signal by Ohm s law Voltage Signals The most commonly interfaced signal is a voltage signal For example thermocouples strain gauges and accelerometers all produce voltage signals There are three major aspects of a voltage signal that you need to consider e Amplit
326. n For example to display a summary of the second event contained by the structure events showdaqgevents events 2 2 Trigger 1 18 12 05 0 Channel 1 Alternatively you can display event summary information via the Workspace browser by right clicking the device object and selecting Explore gt Show DAQ Events from the context menu Events and Callbacks Creating and Executing Callback Functions When using callback functions you should be aware of these execution rules e Callback functions execute in the order in which they are issued e All callback functions except those associated with timer events are guaranteed to execute e Callback function execution might be delayed if the callback involves a CPU intensive task such as updating a figure You specify the callback function to be executed when a specific event type occurs by including the name of the M file as the value for the associated callback property You can specify the callback function as a function handle or as a string cell array element Function handles are described in the MATLAB function_handle reference pages Note that if you are executing a local callback function from within an M file then you must specify the callback as a function handle For example to execute the callback function mycallback for the analog input object ai every time 1000 samples are acquired ai SamplesAcquiredFcnCount 1000 ai SamplesAcquiredFcn mycallback Alterna
327. n with the command daqinfo daqread file info Note When you retrieve object information the entire event log is returned to daqinfo 0bjInfo EventLog regardless of the number of samples retrieved Example Logging and Retrieving Information This example illustrates how to log information to a disk file and then retrieve the logged information to MATLAB using various calls to daqread A sound card is configured for stereo acquisition data is logged to memory and to a disk file four triggers are issued and 2 seconds of data are collected for each trigger at a sampling rate of 8 kHz You can run this example by typing daqdoc8_1 at the MATLAB command line 1 Create a device object Create the analog input object ai for a sound card The installed adaptors and hardware IDs are found with daqhwinfo ai analoginput winsound ai analoginput nidaq 1 ai analoginput mcc 1 2 Add channels Add two hardware channels to ai ch addchannel ai 1 2 ch addchannel ai 0O 1 For NI and MCC 3 Configure property values Define a 2 second acquisition for each trigger set the trigger to repeat three times and log information to the file file00 daq duration 2 Two seconds of data for each trigger set ai SampleRate 8000 ActualRate get ai SampleRate set ai SamplesPerTrigger duration ActualRate set ai TriggerRepeat 3 set ai LogFileName file00 daq set ai Lo
328. n an error is returned Note For some sound cards you can set the sampling rate to any value between the minimum and maximum values defined by the hardware You can enable this feature with the StandardSampleRates property Refer to Chapter 12 Device Specific Property Reference for more information For hardware that supports simultaneous sampling of channels sound cards and Agilent Technologies devices the maximum sampling rate for each channel is given by the maximum board rate For scanning hardware most National Instruments and Measurement Computing devices the per channel sampling rate is given by the maximum hardware rate divided by the number of channels contained by the device object After setting a value for SampleRate you should find out the actual rate set by the engine ActualRate get ai SampleRate Alternatively you can use the setverify function which sets a property value and returns the actual value set ActualRate setverify ai SampleRate 100000 You can find the range of valid sampling rates for your hardware with the propinfo function ValidRates propinfo ai SampleRate ValidRates ConstraintValue ans 1 0e 005 0 0000 2 0000 4 9 4 Getting Started with Analog Input 4 10 Trigger Types For analog input objects a trigger is defined as an event that initiates data logging to memory or to a disk file Defining an analog input trigger involves specifying the tri
329. n analog output subsystem it must first be queued in the data acquisition engine with the putdata function If you want to continuously output the same data you can use multiple calls to putdata However because each putdata call consumes memory a long output sequence can quickly bring your system to halt As an alternative to putdata you can continuously output previously queued data using RepeatOutput Because RepeatOutput requeues the data additional memory resources are not consumed While the data is being output you cannot add additional data to the queue Usage AO Common Access Read write Data type Double Read only Yes when running The default value is zero Create the analog output object ao for a sound card and add one channel to it ao analogoutput winsound chans addchannel ao 1 To queue one second of data data sin linspace 0 10 8000 putdata ao data To continuously output data for 10 seconds set ao RepeatOutput 9 Functions putdata Purpose Indicate whether the device object is running Description Along with the Logging or Sending property Running reflects the state of an analog input or analog output object Running can be On or Off Running is automatically set to On once the start function is issued When Running is On you can acquire data from an analog input device or send data to an analog output device after the trigger occurs For digital I O objects Running is ty
330. n analog trigger signal to a PCI DAS1602 16 board AI Ch 0 7 corresponds to pins 2 17 while Analog Trigger In corresponds to pin 43 Analog channels Analog trigger 7 AI Ch 0 7 A D Analog Trigger In lt PCI DAS1602 16 board 5 41 5 Doing More with Analog Input 5 42 National Instruments When using National Instruments NI hardware there are additional trigger types and trigger conditions available to you These device specific property values fall into two categories hardware digital triggering and hardware analog triggering The device specific trigger types and trigger conditions are described below and in Chapter 11 Base Property Reference Table 5 10 Analog Input TriggerType and TriggerCondition Property Values for NI Hardware TriggerType TriggerCondition Description Value Value HwDigital None The trigger occurs when the falling edge of a digital TTL signal is detected HwAnalogChannel AboveHighLevel The trigger occurs when the analog signal is above or HwAnalogPin the specified value BelowLowLevel The trigger occurs when the analog signal is below the specified value HighHysteresis The trigger occurs when the analog signal is greater than the specified high value with hysteresis given by the specified low value InsideRegion The trigger occurs when the analog signal is inside the specified region LowHyst
331. n call peekdata peekdata is a nonblocking function because it immediately returns control to MATLAB Therefore samples might be missed or repeated When a peekdata call is processed the most recent samples requested are immediately returned but the data is not extracted from the engine In other words peekdata provides a snapshot of the most recent requested samples This situation is illustrated below Time gt ee bt I Take a snapshot of the most recent requested data I Data stored in engine If another peekdata call is issued then once again only the most recent requested samples are returned This situation is illustrated below Time gt a oy Take another snapshot of the most recent requested data I Data stored in engine 5 Doing More with Analog Input 5 10 Rules for Using peekdata Using peekdata to preview data follows these rules e You can call peekdata before a trigger executes Therefore peekdata is useful for previewing data before it is logged to the engine or a disk file e In most cases you will call peekdata while the device object is running However you can call peekdata once after the device object stops running e If the specified number of preview samples is greater than the number of samples currently acquired all available samples are returned with a warning message stating that the requested number of samples were not available F
332. n hardware that simultaneously samples all input signals and then holds the values until the A D converter digitizes all the signals A data acquisition hardware component that performs a specific task The Data Acquisition Toolbox supports analog input analog output and digital I O subsystems An analog input trigger event initiates data logging to memory or a disk file An analog output trigger event initiates the output of data from the engine to the hardware The following abbreviations are used in this index AI analog input AO analog output DIO digital I O HP Hewlett Packard MCC Measurement Computing Corporation NI National Instruments A A D converter 1 6 input range 5 55 sampling rate 4 8 absolute time 5 18 accuracy 1 29 acquiring data 3 22 continuous samples per trigger 5 22 simultaneous input and output 6 37 trigger repeats 5 29 single point 10 63 actuator 1 3 adaptor kit 2 7 adaptors registering A 18 supported hardware 2 7 third party A 19 addchannel AI object 4 3 AO object 6 3 addchannel function 10 8 addline function 10 13 addmuxchannel function 10 16 Agilent Technologies hardware channel configuration 5 4 decimation factor 12 24 driver A 2 properties 12 3 trigger types AI object 5 37 AO object 6 25 troubleshooting A 2 AISENSE 12 12 alias 1 36 AMUX 64T adding channels 10 16 channel indices 10 74 analog input object acquisition continuous 5 22 single point 10 63 a
333. n running The default value is determined by the hardware driver Create the analog output object ao for a National Instruments board and add two hardware channels to it ao analogoutput nidaq 1 addchannel ao 0 1 OutputRange See Also You can return the output ranges supported by the board with the OutputRanges field of the daghwinfo function out daghwinfo ao out OutputRanges ans 0 0000 10 0000 10 0000 10 0000 To configure both channels contained by ao to output signals between 10 volts and 10 volts ao Channel OutputRange 10 10 Alternatively you can use the setverify function to configure and return the OutputRange value ActualRange setverify ao Channel OutputRange 10 10 Functions daqhwinfo setverify Properties Units UnitsRange 11 57 Parent Purpose Description Characteristics Values Example 11 58 Indicate the parent device object of a channel or line The parent of a channel line is defined as the device object that contains the channel line You can create a copy of the device object containing a particular channel or line by returning the value of Parent You can treat this copy like any other device object For example you can configure property values add channels or lines to it and so on Usage AI AO Channel DIO Line Access Read only Data type Device object Read only N A when running The value is defined when channe
334. n time errors do not include configuration errors such as setting an invalid property value Samples Output Event A samples output event is generated immediately after the number of samples specified by the SamplesOutputFcnCount property is output for each channel group member This event executes the callback function specified for SamplesOutputFen Start Event A start event is generated immediately after the start function is issued This event executes the callback function specified for StartFcn When the callback function has finished executing Running is automatically set to On and the device object and hardware device begin executing The device object is not started if an error occurs while executing the callback function Stop Event A stop event is generated immediately after the device object and hardware device stop running This occurs when e The stop function is issued e The requested number of samples is output e A run time error occurs A stop event executes the callback function specified for StopFcn Under most circumstances the callback function is not guaranteed to complete execution until sometime after the device object and hardware device stop running and the Running property is set to Off Timer Event A timer event is generated whenever the time specified by the TimerPeriod property passes This event executes the callback function specified for TimerFcn Time is measured relative to when the device object
335. n values ranging from 0 5 to 100 Many boards include a programmable gain amplifier that allows you to change the device gain through software When an input signal exceeds the valid input range of the converter an overrange condition occurs In this case most devices saturate to the largest representable value and the converted data is almost definitely incorrect The gain setting affects the precision of your measurement the higher lower the gain value the lower higher the precision Refer to How Are Range Gain and Measurement Precision Related on page 1 31 for more information about how input range gain and precision are related to each other An analog input subsystem can typically convert both unipolar signals and bipolar signals A unipolar signal contains only positive values and zero while a bipolar signal contains positive values negative values and zero Unipolar and bipolar signals are depicted below Refer to the figure in Quantization on page 1 19 for an example of a unipolar signal 10 Volts VAN 5 Volts 0 Volts 5 Volts Unipolar Bipolar Unipolar 1 21 T introduction to Data Acquisition 1 22 In many cases the signal polarity is a fixed characteristic of the sensor and you must configure the input range to match this polarity As you can see it is crucial to understand the range of signals expected from your sensor so that you can configure
336. nctions sa sses catana iae a E eee 2 3 The Data Acquisition Engine 0 0 0 c cece sesan 2 4 The Hardware Driver Adaptor 0 c cee eee 2 7 Accessing Your Hardware 0 0c cece une 2 8 Acquiring Data 01 005 one ee wt Sees bles ie ah oS 2 8 Outputtine Datas 04 05 eh es ewe tien tied eee eee ad 2 9 Reading and Writing Digital Values 2 10 Understanding the Toolbox Capabilities 2 12 The Contents M File 0 0 cece cece 2 12 Documentation Examples 0 00 cece eee eens 2 12 The Quick Reference Guide 0 00 cece eee eens 2 13 DEMOS beet E E eee ee eh ee AAA Soe oe 2 13 Examining Your Hardware Resources 2 17 General Toolbox Information 0 0 000 eee eee 2 17 Adaptor Specific Information 0 0000 ee eee 2 18 Device Object Information 0 0000 cece eee 2 19 ii Contents Getting Hel pi 634 2 36 05 Ate We eS eb Ss 2 20 The daghelp Function 0 c cece eee eens 2 20 The propinfo Function 0 0 c cee eens 2 21 3 VOT VTC W arsed ne seat A aE E AE E AEE E EAA a 3 2 Creating a Device Object 000s 3 4 Creating an Array of Device Objects 00 0000s 3 5 Where Do Device Objects Exist 0 0 cee eee eens 3 6 Adding Channels or Lines 0 00 cece eens 3 8 Mapping Hardware Channel IDs to MATLAB Indices 3 9 Configuri
337. nd StopTriggerConditionValue For both HwDigital and HwAnalog SamplesPerTrigger is automatically set to Inf Therefore your acquisition will run until the stop trigger is received or the stop function is issued You can continue the acquisition beyond the specified stop trigger by setting StopTriggerDelay to a positive value Characteristics Vendor Usage Access Data Type Read only when running Va lues None HwDigital HwAnalog See Also Properties Keithley AI Common Read write String Yes The acquisition stops when the number of samples specified by SamplesPerTrigger is acquired or the stop function is issued The acquisition stops on the rising or falling edge of the TGIN input line The acquisition stops when the channel specified by the StopTriggerChannel property meets the specified stop trigger conditions SamplesPerTrigger StopTriggerChannel StopTriggerCondition StopTriggerConditionValue StopTriggerDelay 12 33 Sum Purpose Description Characteristics Values 12 34 Specify whether the source sum input is enabled or disabled Sum can be Off or On If Sum is Off the sum input is disabled If Sum is On the sum input is enabled The signal on the sum input is internally added to the output that the source would otherwise produce For the Option 1D4 single channel source the source sum input is shared with the source COLA output Only one of these two sources can be enabled at any
338. ne However when you reference channels you use the MATLAB indices and not the hardware IDs Given this you should keep in mind that MATLAB is one based You can return the vendor s hardware IDs with the daqhwinfo function 3 9 3 The Data Acquisition Session 3 10 For example suppose you create the analog input object ai for a National Instruments board and you want to add the first three differential channels ai analoginput nidaq 1 To return the hardware IDs supply the device object to daqhwinfo and examine the DifferentiallIDs field out daghwinfo ai out DifferentialIDs ans 0 1 2 3 4 5 6 7 The first three differential channels have IDs 0 1 and 2 respectively addchannel ai 0 2 The index assigned to a hardware channel depends on the order in which you add it to the device object In the above example the channels are automatically assigned the MATLAB indices 1 2 and 3 respectively You can change the hardware channels associated with the MATLAB indices using the HwChannel property For example to swap the order of the second and third hardware channels ai Channel 2 HwChannel 2 ai Channel 3 HwChannel 1 Adding Channels or Lines The original and modified index assignments are shown below Hardware channel ID MATLAB index 0 lt 1 Original index assignment 1 lt 2 2 lt gt 3 0 lt gt 1 Modified index 2 3 Note If you are using scanning hardware th
339. ne a new measurement type these two ways o If the Measurements panel is displayed select New from the Type menu e Use the Measurement Type pane of the Measurement Editor 9 19 9 softscope The Data Acquisition Oscilloscope 9 20 As shown below a new measurement type that calculates the absolute value is defined via the Measurements panel The resulting measurement is the absolute value of the CHO data Measurements Channel CHO bd Type Pk2Pk z Value 7 48516 M Show in Disp Channel CHO ad New Measurement Type x Type vert X T 7 ype abs l The new measurement type vee IM MATLAB Function abs yp M Show in Diet calculates the absolute value Cursor Type None x Channel CHO z OK Cancel Type Value Select New from the Type menu Configuring Measurement Properties There are two sets of properties associated with measurements e Measurement panel properties Properties associated with the panel label e Measurement properties Properties associated with the measurements that are listed in the panel For descriptions of all measurement properties click the Help button of the Scope Properties pane or the Measurement Properties pane Making Measurements Measurement Panel Properties You can change the characteristics of the panel label with the Scope Editor GUI To open this GUI select Scope from the Edit menu choose the Scope Properties
340. ne the events logged for the example given by Example Queuing Data with putdata on page 6 18 You can do this by accessing the EventLog property events AO EventLog events 3x1 struct array with fields Type Data By examining the contents of the Type field you can list the events that were recorded while AO was running events Type ans Start Trigger Stop To display information about the trigger event you must access the Data field which stores the absolute time the trigger occurred and the number of samples output when the trigger occurred trigdata events 2 Data trigdata AbsTime 1999 4 16 9 53 19 9508 RelSample 0 You can display a summary of the event log with the showdaqevents function For example to display a summary of the second event contained by the structure events showdagevents events 2 2 Trigger 09 53 19 O Alternatively you can display event summary information via the Workspace browser by right clicking the device object and selecting Explore gt Show DAQ Events from the context menu Events and Callbacks Examples Using Callback Properties and Callback Functions Examples showing how to create callback functions and configure callback properties are given below Displaying the Number of Samples Output This example illustrates how to generate samples output events You can run this example by typing daqdoc6_4 at the MATLAB command line The local cal
341. nerating Timer Events Generating Timer Events The fact that analog input and analog output objects make use of data stored in the engine and clocked I O leads to the concept of a running device object and the generation of events However because the Data Acquisition Toolbox does not support buffered digital I O DIO operations DIO objects do not store data in the engine Additionally reading and writing line values are not clocked at a specific rate in the way that data is sampled by an analog input or analog output subsystem Instead values are either written directly to digital lines with putvalue or read directly from digital lines with getvalue Therefore the concept of a running DIO object does not make sense in the same way that it does for analog I O However you can run a DIO object to perform one task generate timer events You can use timer events to update and display the state of the DIO object Refer to the diopanel demo for an example Timer Events The only event supported by DIO objects is a timer event Timer events occur after a specified period of time has passed Properties associated with generating timer events are given below Table 7 4 Digital I O Timer Event Properties Property Name Description Running Indicate if the device object is running TimerFen Specify the M file callback function to execute whenever a predefined period of time passes TimerPeriod Specify the period of
342. nformation 00 0c e eee 8 7 Example Logging and Retrieving Information 8 9 softscope The Data Acquisition Oscilloscope 9 Opening the Oscilloscope 0 0000 eens 9 2 Hardware Configuration 0 000 e cece eee ene 9 3 Displaying Channels 0 0 0 0 cece n eens 9 4 Creating Additional Displays 0 0 0 eee eens 9 5 Configuring Display Properties 0 00 saesae 9 6 Math and Reference Channels 0 00 eee eeee 9 7 Removing Channel Displays 0 0 20 e eee 9 10 Scaling the Channel Data 0 000 9 11 Configuring Channel Properties 00000e eee 9 12 Triggering the Oscilloscope 000 cee 9 14 Acquisition Types 0 0 ccc eee cee ene en nes 9 14 Triger Types me ereen r Sa Rew ed wae ee os 9 14 Configuring Trigger Properties 0 000 cee e eee 9 16 vii viii Contents Making Measurements 000 eee ences 9 17 Defining a Measurement 0 0 00 cece eee ees 9 18 Defining a New Measurement Type 0 0000 9 19 Configuring Measurement Properties 00055 9 20 Exporting Data iea te a a e E A nns 9 23 Channels siss gaat e En E BAS ae See baa eee 9 23 Measurements on cece cee ee eee eens 9 24 Saving and Loading the Oscilloscope Configuration 9 25 Function Reference 10 Getting Command Line Function Help
343. ng an error message is returned and data logging is stopped Usage AI Common Access Read write Data type String Read only Yes when running Index Multiple log files are written each with an indexed filename based on the LogFileName property Overwrite The log file is overwritten Functions daqread Properties LogFileName LoggingMode ManualTriggerHwOn Purpose Description Characteristics Values Example Specify that the hardware device starts when a manual trigger is issued ManualTriggerHwOn can be set to Start or Trigger If ManualTriggerHwOn is Start then the hardware device associated with your device object starts running after you issue the start function If ManualTriggerHwOn is Trigger then the hardware device associated with your device object starts running after you execute a manual trigger with the trigger function You can use trigger only when you configure the TriggerType property to Manual You should configure ManualTriggerHwOn to Trigger when you want to synchronize the input and output of data or you require more control over when your hardware starts Note that you cannot use peekdata or acquire pretrigger data when you use this value Additionally you should not use this value with repeated triggers because the subsequent behavior is undefined Usage AI Common Access Read write Data type String Read only Yes when running Start Start the hardware after the start function is
344. ng and Returning Properties 3 12 Property Py pes ieie rece aed bee Gite dew once d feeb Bed eet g quedo 3 12 Returning Property Names and Property Values 3 14 Configuring Property Values 0 0 00 cece eee eee 3 18 Specifying Property Names 0 00 c ce eee eee ees 3 19 Default Property Values 0 cece eee eens 3 19 The Data Acquisition Property Editor 3 20 Acquiring and Outputting Data 3 22 Starting the Device Object 1 1 0 0 0 ees 3 23 Logging or Sending Data 0 0 cece eee eens 3 23 Stopping the Device Object 00 ccc eee ees 3 24 Cleaning Up sinc g e t os ba he OR A Ee A 3 25 iii Getting Started with Analog Input 4 Creating an Analog Input Object 4 2 Adding Channels to an Analog Input Object 4 3 Referencing Individual Hardware Channels 4 5 Example Adding Channels for a Sound Card 4 6 Configuring Analog Input Properties 4 8 The Sampling Rate osusi apisaon ccc eee ene 4 8 Trigger Types ccs che gos ea Ba dates eae Pa Baba eae ed 4 10 The Samples to Acquire per Trigger 0000000 4 11 Acquiring Data ii c65 085 oon ds ee Pee aes 4 12 Starting the Analog Input Object 000000 4 12 Hogeme Data cnc reaa a ORR PAIR eee hile Bed ak os 4 13 Stopping the Analog Input Object 000000
345. ng these samples into the MATLAB workspace with the getdata function and then save them to the MAT file using a separate variable name You can also log samples to disk by configuring the LoggingMode property to Disk or Disk amp Memory e Values for read only properties are restored to their default values upon loading For example the EventLog property is restored to an empty vector Use the propinfo function to determine if a property is read only e Values for the BufferingConfig property if the Buf feringMode property is set to Auto and the MaxSamplesQueued property might not be restored because both these property values are based on available memory If you use the help command to display the M file help for save then you must supply the pathname shown below help daq private save Functions getdata load propinfo set Purpose Syntax Arguments Description Configure or display device object properties set obj props set obj set obj PropertyName props set obj PropertyName set obj PropertyName PropertyValue set obj PN PV set obj S obj PropertyName PropertyValue PN PV S props A device object array of device objects channels or lines A property name A property value A cell array of property names A cell array of property values A structure whose field names are device object channel or line properties A structure array whose field names are
346. nnel InputRange ans Type double Constraint Bounded ConstraintValue 1 1 DefaultValue 1 1 ReadOnly 0 ReadOnlyRunning 1 DeviceSpecific 0 Functions daqhelp 10 81 putdata Purpose Syntax Arguments Description Remarks 10 82 Queue data in the engine for eventual output putdata obj data obj An analog output object data The data to be queued in the engine putdata obj data queues the data specified by data in the engine for eventual output to the analog output subsystem data must consist of a column of data for each channel contained by obj More About Queueing Data e Data must be queued in the engine before obj is executed e putdata is a blocking function because it returns execution control to the MATLAB workspace only when the requested number of samples are queued in the engine for each channel group member e If the value of the RepeatOutput property is greater than 0 then all queued data is automatically requeued until the RepeatOutput value is reached RepeatOutput must be configured before start is issued e After obj executes you can continue to queue data unless RepeatOutput is greater than 0 e You can queue data in the engine until the value specified by the MaxSamplesQueued property is reached or the limitations of your hardware or computer are reached More About Outputting Data e Data is output as soon as a trigger occurs e An error is returned if a
347. nnel The following example illustrates how to configure such a trigger where the trigger channel is assigned the 5 43 5 Doing More with Analog Input 5 44 descriptive name TrigChan and the default TriggerCondition property value is used ai analoginput nidaq 1 addchannel ai 0 7 set ai Channel 1 ChannelName TrigChan set ai TriggerChannel ai Channel 1 set ai TriggerType HwAnalogChannel1 set ai TriggerConditionValue 0 2 The diagram below illustrates how you can connect an analog trigger signal to an MIO 16E Series board Analog pin PFIO TRIG1 A D k MIO 16E Series board Events and Callbacks Events and Callbacks You can enhance the power and flexibility of your analog input application by utilizing events An event occurs at a particular time after a condition is met and might result in one or more callbacks While the analog input object is running you can use events to display a message display data analyze data and so on Callbacks are controlled through callback properties and callback functions All event types have an associated callback property Callback functions are M file functions that you construct to suit your specific data acquisition needs You execute a callback when a particular event occurs by specifying the name of the M file callback function as the value for the associated callback prop
348. nnel You can export the channel data to one of four destinations e The MATLAB workspace as an array e The MATLAB workspace as a structure e A MATLAB figure window e A MAT file All channels added to the oscilloscope are listed in the GUI Channel Exporter x Data destination PAME EAEE Samples to export Number in display C Count foo Selectthe channels to export Name Data Source Variable Name ViHardware Le Hardware ch c0 MHardware Right Hardware ch c1 Export Close Help 10 99 softscope 10 100 Measurement Exporter The Measurement Exporter allows you to export the data associated with a measurement You can export the measurement to one of three destinations e The MATLAB workspace e A MATLAB figure window e A MAT file The number of measurements exported depends on the BufferSize property value By default BufferSize is 1 indicating that the last measurement value calculated is available to export Measurement Exporter j Data destination RALES EM Selectthe measurements to export Channel Type variable Name M Left Pk2Pk mo M Right Mean m1 Export Close Help softscope Scope Editor The Scope Editor consists of two panes Scope Add and remove displays the channel panel the measurement panel and the trigger panel Note that you can define as many displays as you want but there can only be only one channel panel measu
349. nnel name or cell array of descriptive channel names 10 8 addchannel Remarks Rules for Adding Channels e The numeric values you supply for hwch depend on the hardware you access For National Instruments and Measurement Computing hardware channels are zero based begin at zero For Agilent Technologies hardware and sound cards channels are one based begin at one e Hardware channel IDs are stored in the HwChannel property and the associated MATLAB indices are stored in the Index property e You can add individual hardware channels to multiple device objects e For for sound cards and Agilent Technologies devices you cannot add a hardware channel multiple times to the same device object e For Agilent Technologies devices added channels must be in increasing order e You can configure sound cards in one of two ways mono mode or stereo mode For mono mode hwch must be 1 For stereo mode the first hwch value specified must be 1 Note If you are using National Instruments AMUX 64T multiplexer boards you must use the addmuxchannel function to add channels More About MATLAB Indices Every hardware channel contained by a device object has an associated MATLAB index that is used to reference the channel Index assignments are made either automatically by addchannel or explicitly with the index argument and follow these rules e If index is not specified and no hardware channels are contained by the d
350. nput argument You can optionally specify an output argument which represents the returned values as a binary vector Binary vectors are described in Writing Digital Values on page 7 12 For example suppose you create the digital I O object dio and add eight input lines to it from port 0 dio digitalio nidaq 1 addline dio 0 7 in To read the current value of all the lines contained by dio portval getvalue dio portval 1 1 1 0 1 0 0 0 To read the current values of the first five lines contained by dio lineval getvalue dio Line 1 5 lineval 1 1 1 0 1 You can convert a binvec to a decimal value with the binvec2dec function For example to convert the binary vector lineval to a decimal value out binvec2dec lineval out 23 Writing and Reading Digital O Line Values Rules for Reading Digital Values Reading values from digital I O lines follows these rules e Ifthe DIO object contains lines from a port configurable device then all lines are read even if they are not contained by the device object However only values from the lines contained by the object are returned e You can always read from a line configured for output e For National Instruments hardware lines configured for input return a value of 1 by default getvalue always returns a binary vector binvec To convert the binvec to a decimal value use the binvec2dec function Example Writing and Reading Digital Values
351. nput object AI for a National Instruments board The installed adaptors and hardware IDs are found with daqhwinfo AI analoginput nidaq 1 2 Add channels Add one channel to AI chan addchannel AI1I 0 Analog Input Examples 3 Configure property values Assign values to the basic setup properties and create the variables blocksize and Fs which are used for subsequent analysis The actual sampling rate is retrieved because it might be set by the engine to a value that differs from the specified value duration 1 1 second acquisition set AI SampleRate 10000 ActualRate get AI SampleRate set AI SamplesPerTrigger duration ActualRate set AI TriggerType Manual blocksize get AI SamplesPerTrigger Fs ActualRate 4 Acquire data Start AI issue a manual trigger and extract all data from the engine Before trigger is issued you should begin inputting data from the function generator into the data acquisition board start AI trigger AI data getdata AI 5 Clean up When you no longer need AI you should remove it from memory and from the MATLAB workspace delete AI clear AI Analyzing the Data For this experiment analysis consists of finding the frequency of the input signal and plotting the results You can find the signal frequency with daqdocfft f mag daqdocfft data Fs blocksize This function which is shown in Analyzing the Data on
352. nteed to work with any other versions For a list of the driver versions that are compatible with the Data Acquisition Toolbox refer to the product page on the MathWorks Web site at http www mathworks com products daq If you think your driver is incompatible with the Data Acquisition Toolbox then you should verify that your hardware is functioning properly before updating drivers If your hardware is functioning properly then you are probably using unsupported drivers Visit the Measurement Computing Web site at http www measurementcomputing com for the latest drivers Suppose you are using InstaCal software with your hardware You can access this software through the Windows Start button Start gt Programs gt Measurement Computing gt InstaCal The driver version is available through the Help menu Help gt About InstaCal A Troubleshooting Your Hardware For example the version of InstaCal used by a PCI DAS4020 12 board is shown below Instacal olx Eile Install Calibrate Test Help PP esses PC Board List F AM ISA Bus lt PCI Primary bus 0 BBd 1 PCI DAS4020 12 slott 13 About Instacal x InstaCal Ready Version 1 10 Instacal for Windows 95 98 NT Copyright 1998 99 ComputerBoards Inc 16 Commerce Boulevard Middleboro MA 02346 USA Measurement Computing Hardware Is Your Hardware Functioning Properly To troubleshoot your Measurement Computin
353. ntial Inputs When you configure your hardware for differential input there are two signal wires associated with each input signal one for the input signal and one for the reference return signal The measurement is the difference in voltage between the two wires which helps reduce noise and any voltage that is common to both wires As shown below the input signal is connected to the positive amplifier socket labeled and the return signal is connected to the negative amplifier socket 1 23 T introduction to Data Acquisition 1 24 labeled The amplifier has a third connector that allows these signals to be referenced to ground Amplifier Input signal Return signal out National Instruments recommends that you use differential inputs under any of these conditions e The input signal is low level less than 1 volt e The leads connecting the signal are greater than 10 feet e The input signal requires a separate ground reference point or return signal e The signal leads travel through a noisy environment Single Ended Inputs When you configure your hardware for single ended input there is one signal wire associated with each input signal and each input signal is connected to the same ground Single ended measurements are more susceptible to noise than differential measurements because of differences in the signal paths The Analog Input Subsystem As shown below the input signal is conn
354. nts are available to the Oscilloscope e Measurement Properties Configure properties for the defined measurements e Measurement Type Add or delete measurement types and select which defined measurement types are available to the Oscilloscope Measurement Editor j x Measurement Properties Measurement Type Define a new measurement Channel cnt x Type None x Add Defined measurements Channel Type M CH1 Pk2Pk M CH2 Mean OK Cancel Apply Help 10 103 start Purpose Syntax Arguments Description Remarks See Also 10 104 Start a device object start obj obj A device object or an array of device objects start obj initiates the execution of the device object obj When start is issued for an analog input or analog output object e The M file callback function specified for StartFcn is executed e The Running property is set to On e The start event is recorded in the EventLog property e Data existing in the engine is flushed Although an analog input or analog output object might be executing data logging or sending is not necessarily initiated Data logging or sending requires a trigger event to occur and depends on the TriggerType property value For any device object you can specify start as the value for a callback property ai StopFcn start Note You typically execute a digital I O object to periodically update an
355. number of samples to acquire was reached or data was missed For analog output AO objects the requested number of samples to output was reached e A run time error occurred A stop event executes the callback function specified for StopFcn Under most circumstances the callback function is not guaranteed to complete execution until sometime after the device object and hardware device stop and the Running property is set to Off Stop event information is stored in the Type and Data fields of the EventLog property The Type field value is Stop The Data field values are given below Data Field Value Description AbsTime The absolute time as a clock vector the event occurred RelSample The acquired AI or output AO sample number when the event occurred Usage AI AO Common Access Read write Data type String Read only No when running The default value is an empty string 11 77 StopFcn See Also Functions stop Properties EventLog Running 11 78 Tag Purpose Description Characteristics Values Example See Also Specify a device object label Tag provides a means to identify device objects with a label Using the daqfind function and the Tag value you can identify and retrieve a device object that was cleared from the MATLAB workspace Usage AI AO DIO Common Access Read write Data type String Read only No when running The default value is an empty string Cre
356. ny decimation In this case the only valid span is clock frequency 2 56 If you attempt to use decimation when the clock frequency is above 102 400 Hz then an error might occur when the measurement starts For the Option 1D4 source board the maximum number of decimate by two passes allowed is 16 and the maximum decimation factor is 5 216 The effective sample rate is defined as the rate at which data is received from an input or used by a source and is normally equal to 2 56 times the span If the data is oversampled then the effective sample rate is 5 12 times the span If the digital filters in a module have a cutoff that is sharper than 1 2 56 then some of the frequencies above the maximum span might contain valid alias protected data This is the case with the E1432 and E1433 modules which have a top span filter cutoff of clock frequency 2 226 which is 23 kHz Span when the clock frequency is 51 2 kHz 88 3 kHz when the clock frequency is 196 608 kHz However Span ignores the extra bandwidth so that the maximum span is always 1 2 56 times the effective sample rate Span applies to an entire E1432 module rather than to one of its channels After a hardware reset each module is automatically set to the maximum legal span Characteristics Vendor Agilent Technologies Usage AI AO Common Access Read write Data Type Double Read only Yes when running Values Normally the maximum valid span is given by the clock freq
357. o 0 3 in These lines are automatically assigned the indices 1 4 If you want to add the first four hardware lines to dio and assign descriptive names to the lines addline dio 0 3 in line1 line2 line3 line4 Note that you can use the makenames function to create a cell array of line names You can add the first four hardware lines line IDs 0 3 from port 1 to the existing line group addline dio 0 3 1 out The new lines are automatically assigned the indices 5 8 Functions delete makenames Properties HwLine Index LineName 10 15 addmuxchannel Purpose Syntax Arguments Description Remarks See Also 10 16 Add hardware channels when using a multiplexer board addmuxchannel obj addmuxchannel obj chanids chans addmuxchannel obj An analog input object associated with a National Instruments board chanids The hardware channel IDs chans The channels that are added to obj addmuxchannel obj adds as many channels to obj as is physically possible based on the number of National Instruments AMUX 64T multiplexer mux boards specified by the NumMuxBoards property For one mux board 64 channels are added For two mux boards 128 channels are added For four mux boards 256 channels are added addmuxchannel obj chanids adds the channels specified by chanids to obj chanids refers to the hardware channel IDs of the data acquisition board The actual number of channels adde
358. o TimerFcn stop Note Issuing stop is the only way to stop an executing digital I O object You typically execute a digital I O object to periodically update and display its state Refer to the diopanel demo for an example 10 105 stop See Also Functions start trigger Properties EventLog Logging RepeatOutput Running SamplesPerTrigger Sending Timeout TriggerRepeat 10 106 trigger Purpose Syntax Arguments Description Remarks See Also Manually execute a trigger trigger obj obj An analog input or analog output object or an array of these device objects trigger obj manually executes a trigger After trigger is issued e The absolute time of the trigger event is recorded by the InitialTriggerTime property e The Logging property or Sending property is set to On e The M file callback function specified by TriggerFcn is executed e The trigger event is recorded in the EventLog property You can issue trigger only if TriggerType is set to Manual Running is On and Logging is Off You can specify trigger as the value for a callback property ai StartFen trigger Functions start stop Properties InitialTriggerTime Logging Running Sending TriggerFcn TriggerType 10 107 waittilstop Purpose Syntax Arguments Description Remarks 10 108 Wait for the device object to stop running waittilstop obj waittime obj A device object or an array of de
359. o represent the decimal number out A logical array containing the binary vector out dec2binvec dec converts the decimal value dec to an equivalent binary vector and stores the result as a logical array in out out dec2binvec dec bits converts the decimal value dec to an equivalent binary vector consisting of at least the number of bits specified by bits More About Binary Vectors A binary vector binvec is constructed with the least significant bit LSB in the first column and the most significant bit MSB in the last column For example the decimal number 23 is written as the binvec value 1 110 1 More About Specifying the Number of Bits e If bits is greater than the minimum number of bits required to represent the decimal value then the result is padded with zeros e If bits is less than the minimum number of bits required to represent the decimal value then the minimum number of required bits is used e If bits is not specified then the minimum number of bits required to represent the number is used To convert the decimal value 23 to a binvec value dec2binvec 23 ans 1 1 1 0 1 10 47 dec2binvec See Also 10 48 To convert the decimal value 23 to a binvec value using six bits dec2binvec 23 6 ans 1 1 1 0 1 0 To convert the decimal value 28 to a binvec value using four bits then the result uses five bits This is the minimum number of bits required to represent the number dec2binvec 23
360. o the analoginput function ai analoginput nidaq 1 The association between device objects and hardware subsystems is shown below Al AO DIO object object object AI AO DIO subsystem subsystem subsystem Creating an Array of Device Objects In MATLAB you can create an array from existing variables by concatenating those variables together The same is true for device objects For example suppose you create the analog input object ai and the analog output object ao for a sound card lt Toolbox device objects lt Hardware subsystems ai analoginput winsound ao analogoutput winsound You can now create a device object array consisting of ai and ao using the usual MATLAB syntax To create the row array x x ai ao Index Subsystem Name 1 Analog Input winsoundo AI 2 Analog Output winsound0O AO 3 5 3 The Data Acquisition Session 3 6 To create the column array y y ai ao Note that you cannot create a matrix of device objects For example you cannot create the matrix z ai aOjai ao 222 Error using gt analoginput vertcat Only a row or column vector of device objects can be created Depending on your application you might want to pass an array of device objects to a function For example using one call to the set function you can configure both ai and ao to the same property value set
361. object You can think of a device object as a channel or line container that reflects the common functionality of a particular device The common functionality of a device applies to all channels or lines that it contains For example the sampling rate of an analog input object applies to all channels contained by Adding Channels or Lines that object In contrast the channels and lines contained by the device object reflect the functionality of a particular channel or line For example you can configure the input range gain and polarity on a per channel basis The relationship between an analog input object and the channels it contains is shown below Analog Input Object Container device object Channel 1 Channel 2 Channel 3 Channel group hardware channels Channel n For digital I O objects the diagram would look the same except that lines would be substituted for channels Mapping Hardware Channel IDs to MATLAB Indices When you add channels to a device object the resulting channel group consists of a mapping between hardware channel IDs and MATLAB indices Hardware channel IDs are numeric values defined by the hardware vendor that uniquely identify a channel For National Instruments and Measurement Computing hardware the channel IDs are zero based begin at zero For Agilent Technologies hardware and sound cards the channel IDs are one based begin at o
362. of interest the sensor bandwidth must be compatible with the measurement bandwidth You might want to use sensors with the widest possible bandwidth when making any physical measurement This is the one way to ensure that the basic measurement system is capable of responding linearly over the full range of interest However the wider the bandwidth of the sensor the more you must be concerned with eliminating sensor response to unwanted frequency components Signal Conditioning Sensor signals are often incompatible with data acquisition hardware To overcome this incompatibility the sensor signal must be conditioned The type of signal conditioning required depends on the sensor you are using For example a signal might have a small amplitude and require amplification or it might contain unwanted frequency components and require filtering Common ways to condition signals include e Amplification e Filtering e Electrical isolation e Multiplexing e Excitation source Amplification Low level signals less than around 100 millivolts usually need to be amplified High level signals might also require amplification depending on the input range of the analog input subsystem For example the output signal from a thermocouple is small and must be amplified before it is digitized Signal amplification allows you to reduce noise and to make use of the full range of your hardware thereby increasing the resolution of the measurement
363. once Continuous Continuously acquire the specified number of samples Sequence Continuously acquire the specified number of samples and use the dependent trigger type each time For each trigger type the Oscilloscope begins to acquire data after you press the Trigger button e Measurement panel The measurement panel lists all measurements that are currently being taken When defining a measurement you must specify The hardware math or reference channel The measurement type Whether the measurement result is drawn as a cursor in the display The oscilloscope GUI shown below is configured to display the sound card channels in separate displays Oscilloscope 3 Eio File Edit Help Channel Scaling Triggers Measurements P guire Continuous v Channel le z Samples to acquire Type Pk2Pk e 5 Fill the display Value j 36818 Count po 87FCO Vv in Display Vertical Right 1 8770Vidiv 10 0msidiv Let 8 8 8 Type independent z Channel Right x C Channel Let Z Type mean z Offset Scale Condition Rising z Valus TNE Value i s g 3 i Yaluez 0 Pretrigger p Se Left 593 33mVidiv 10 0msidiv On Stop Add Measurement Display panel Channel panel Trigger panel Measurement panel softscope Channel Exporter The Channel Exporter allows you to export the data associated with a hardware channel a math channel or a reference cha
364. ond one installed has an ID of 1 and so on You must specify ID when creating analog output objects associated with devices not having an ID of 0 There are two ways you can determine the ID for a particular device e Type daqhwinfo adaptor e Execute the vendor supplied device configuration utility National Instruments To create an analog output object for a National Instruments board defined as device number 1 AO analogoutput nidaq 1 Agilent Technologies To create an analog output object for an Agilent Technologies module with device identifier 1 residing in VXI chassis 0 AO analogoutput hpe1432 vxi0 1 instr Alternatively you can use the syntax AO analogoutput hpe1432 1 0 10 21 analogoutput See Also 10 22 The HP driver allows you to span multiple hardware devices To create an analog output object that spans two HP devices with device identifiers 1 and 2 residing in VXI chassis 0 AO analogoutput hpe1432 vxi0 1 2 instr Alternatively you can use the syntax AO analogoutput hpe1432 1 2 0 Functions addchannel daqhwinfo Properties Name binvec2dec Purpose Syntax Arguments Description Remarks Example See Also Convert binary vector to decimal value out binvec2dec bin bin A binary vector out A double array out binvec2dec bin converts the binary vector bin to the equivalent decimal number and stores the result in out
365. onds with A 5 Choose the File Options menu An array is an ordered collection of information c ia ib union sysc d2c sysd method xviii Introduction to Data Acquisition Before you set up any data acquisition system you should understand the physical quantities you want to measure the characteristics of those physical quantities the appropriate sensor to use and the appropriate data acquisition hardware to use The purpose of this chapter is to provide you with some general guidelines about making measurements with a data acquisition system The information provided should assist you in understanding the above considerations and understanding the specification sheet associated with your hardware The sections are as follows Anatomy of a Data Acquisition Tasks you perform for each new data acquisition experiment Experiment p 1 2 The Data Acquisition System Typical components that compose a data acquisition system p 1 3 The Analog Input Subsystem Hardware subsystem that converts digitizes real world sensor p 1 15 signals into numbers your computer can read Making Quality Maximizing precision and accuracy minimizing noise and matching Measurements p 1 28 the sensor range to the hardware range Selected Bibliography p 1 38 Resources for additional information T introduction to Data Acquisition Anatomy of a Data Acquisition Experiment For each new data acquisition exper
366. onfiguring the channel skew are given below Table 5 3 Channel Skew Properties Property Name Description ChannelSkew Specify the time between consecutive scanned hardware channels ChannelSkewMode Specify how the channel skew is determined ChannelSkew and ChannelSkewMode are configurable only for scanning hardware and not for simultaneous sample and hold SS H hardware For SS H hardware ChannelSkewMode can only be None and Channe1Skew can only be 0 The values for Channe1lSkewMode are given below Table 5 4 ChannelSkewMode Property Values ChannelSkewMode Description Value None No channel skew is defined This is the only valid value for simultaneous sample and hold SS H hardware Equisample The channel skew is automatically calculated as sampling rate number of channels Manual The channel skew must be set with the ChannelSkew property Minimum The channel skew is given by the smallest value supported by the hardware If ChannelSkewMode is Minimum or Equisample then Channel1Skew indicates the appropriate read only value If ChannelSkewMode is set to Manual you must specify the channel skew with ChannelSkew 5 7 5 Doing More with Analog Input 5 8 Managing Acquired Data At the core of any analog input application lies the data you acquire from a sensor and input into your computer for subsequent analysis The role of the analog input subsystem is to convert analog data to
367. operty Name Description Samples Specify the sample range Time Specify the relative time range Triggers Specify the trigger range Channels Specify the channel range Channel names can be specified as a cell array DataFormat Specify the data format as doubles or native TimeFormat Specify the time format as vector or matrix The Samples Time and Triggers properties are mutually exclusive data time daqread returns sample time pairs time is a vector with the same length as data and contains the relative time for each sample Relative time is measured with respect to the first trigger that occurs data time abstime daqread returns sample time pairs and the absolute time of the first trigger abstime is returned as a clock vector data time abstime events daqread returns sample time pairs the absolute time of the first trigger and a log of events events contains the appropriate events based on the Samples Time or Triggers value specified The entire event log is returned only if Samples Time or Triggers is not specified data time abstime events daqinfo daqread returns sample time pairs the absolute time the event log and the structure daqinfo which contains two fields Obj Info and HwInfo Obj Info is a structure containing property name property value pairs and HwInfo is a structure containing hardware information The entire event log is returned to daqinfo ObjInfo EventLog
368. operty specified by PropertyName to out If PropertyName is replaced by a 1 by n or n by 1 cell array of strings containing property names then get returns a 1 by n cell array of values to out If obj is an array of data acquisition objects then out will be an m by n cell array of property values where m is equal to the length of obj and n is equal to the number of properties specified out get obj Channel index PropertyName returns the value of PropertyName to out for the specified channels contained by obj If multiple 10 57 get Remarks Example See Also 10 58 channels and multiple property names are specified then out is an m by n cell array where m is the number of channels and n is the number of properties out get obj Line index PropertyName returns the value of PropertyName to out for the specified lines contained by obj If multiple lines and multiple property names are specified then out is an m by n cell array where m is the number of lines and n is the number of properties get displays all property names and their current values for the specified device object channel or line Base properties are displayed first followed by device specific properties If you use the help command to display the M file help for get then you must supply the pathname shown below help daq daqdevice get Create the analog input object ai for a sound card and configure it to operate in stereo mode ai
369. ophone inputs You can use unpowered microphones with any sound card microphone input Some laptops must use unpowered microphones because they do not have Sound Blaster compatible sound cards As shown below you can easily identify these two microphone types by their jacks Unpowered microphone jack i Powered microphone jack You can find out which sound card brand you have installed by selecting the Devices tab on the Multimedia Properties dialog box Refer to Sound Cards on page A 11 for a picture of this dialog box A 14 Sound Cards Testing with a Microphone To test your sound card with a microphone follow these steps Plug the microphone into the appropriate sound card jack For a Sound Blaster sound card this jack is labeled MIC IN Record audio data by selecting the Record button on the Sound Recorder and then speak into the microphone While recording the green line in the Sound Recorder should indicate that data is being captured If this is the case then the analog input subsystem on your sound card is functioning properly After recording the audio data save it to disk The data is automatically saved as a WAV file Play the saved WAV file While playing the green line in the Sound Recorder should indicate that data is being captured If this is the case then the analog output subsystem on your sound card is functioning properly If you are not able to record or p
370. or 16 bits of resolution Analog input subsystems are also referred to as AI subsystems A D converters or ADCs Analog input subsystems are discussed in detail beginning in The Analog Input Subsystem on page 1 15 Analog Output Subsystems Analog output subsystems convert digital data stored on your computer to a real world analog signal These subsystems perform the inverse conversion of analog input subsystems Typical acquisition boards offer two output channels with 12 bits of resolution with special hardware available to support multiple channel analog output operations Analog output subsystems are also referred to as AO subsystems D A converters or DACs Digital Input Output Subsystems Digital input output DIO subsystems are designed to input and output digital values logic levels to and from hardware These values are typically handled either as single bits or lines or as a port which typically consists of eight lines While most popular data acquisition cards include some digital I O capability it is usually limited to simple operations and special dedicated hardware is often necessary for performing advanced digital I O operations Counter Timer Subsystems Counter timer C T subsystems are used for event counting frequency and period measurement and pulse train generation The Data Acquisition System Sensors A sensor converts the physical phenomena of interest into a signal that is input into yo
371. or more information about peekdata refer to its reference pages in Chapter 10 Function Reference Example Polling the Data Block Under certain circumstances you might want to poll the data block Polling the data block is useful when calling peekdata because this function does not block execution control For example you can issue peekdata calls based on the number of samples acquired by polling the SamplesAcquired property You can run this example by typing daqdoc5_1 at the MATLAB command line Create a device object Create the analog input object AI for a sound card The available adaptors and hardware IDs are found with daqhwinfo AI analoginput winsound AI analoginput nidaq 1 AI analoginput mcc 1 X Add channels Add one hardware channel to AI addchannel AI 1 S addchannel AI 0 For NI and MCC Configure property values Define a 10 second acquisition set up a plot and store the plot handle and title handle in the variables P and T respectively duration 10 Ten second acquisition ActualRate get AI SampleRate set AI SamplesPerTrigger duration ActualRate Managing Acquired Data figure set gcf doublebuffer on Reduce plot flicker P plot zeros 1000 1 T title sprintf Peekdata calls num2str 0 xlabel Samples axis 0O 1000 1 1 grid on 4 Acquire data Start AI and update the display for each 1000 samples acquired by pol
372. or of zeros Create the analog input object ai for a sound card and add two hardware channels to it ai analoginput winsound chans addchannel ai 1 2 After starting ai the trigger immediately executes and the trigger time is recorded start ai abstime ai InitialTriggerTime abstime 1 0e 003 1 9990 0 0020 0 0190 0 0130 0 0260 0 0208 To convert the clock vector to a more convenient form t fix abstime sprintf d d d t 4 t 5 t 6 ans 13 26 20 InitialTriggerTime See Also Functions getdata Properties EventLog Logging Sending 11 37 InputOverRangeFcn Purpose Description Characteristics Values See Also 11 38 Specify the M file callback function to execute when acquired data exceeds the valid hardware range An input overrange event is generated immediately after an overrange condition is detected for any channel group member This event executes the callback function specified for InputOverRangeFcn An overrange condition occurs when an input signal exceeds the range specified by the InputRange property Overrange detection is enabled only if the analog input object is running and a callback function is specified for InputOverRangeFcn Input overrange event information is stored in the Type and Data fields of the EventLog property The Type field value is OverRange The Data field values are given below Data Field Value Description RelSample The
373. or reference channels You use the Channel pane of the Channel Editor GUI to create math and reference channels You open this GUI by selecting the Edit gt Channel menu item For example suppose you want to create a reference waveform to compare to the CHO waveform The first step is to create the reference data in MATLAB t 0 0 0001 0 2 w 200 2 pi ref 3 75 sin w t 9 7 9 softscope The Data Acquisition Oscilloscope 9 8 The next step is to define the reference channel in the Channel Editor GUI The Channel pane shown below is configured to create a reference channel called r1 using the data defined in the variable ref and to display the reference channel data with CHO in display2 Channel Editor x Channel Channel Properties Channel Display Define a new channel Type Reference X Define a reference channel named ame r l r1 using the data from ref Expression fref Display MEEA Display the reference data with CHO lick the Add button to include the new channel in the table Defined channels z Type Name Data Source Display 7 v Hardware CHO HardwarechannelO display2 M Hardware CH1 Hardware channel 1 display Click the OK or Apply button to create the reference channel OK Cancel Apply Help Note that instead of creating the variable ref in the workspace you can specify the expression 3 75 sin w t in
374. orted values For the SampleRate and InputRange properties the value is automatically rounded up to the next highest supported value For all other properties the value is automatically selected to be the nearest supported value e If the value is not within the range of supported values an error is returned and the current property value remains unchanged Create the analog input object ai for a National Instruments AT MIO 16DE 10 board add eight hardware channels to it and set the sample rate to 10 000 Hz using setverify ai analoginput nidaq 1 ch addchannel ai 0 7 ActualRate setverify ai SampleRate 10000 Suppose you use setverify to set the input range for all channels contained by ai to 8 to 8 volts ActualInputRange setverify ai Channel InputRange 8 8 The InputRange value was actually rounded up to 10 to 10 volts ActualInputRange 1 ans 10 10 Functions get propinfo set Properties InputRange OutputRange SampleRate 10 91 showdagevents Purpose Syntax Arguments Description Remarks 10 92 Display event log information showdaqevents obj showdagevents obj index showdaqevents struct showdagqevents struct index out showdaqevents obj An analog input or analog output object index The event index struct An event structure out A one column cell array of event information showdagevents obj displays a summary of the event log
375. ory The data is stored temporarily because it can be overwritten The rate at which the data is overwritten depends on several factors including the available memory the rate at which data is acquired and the number of hardware channels from which data is acquired The stored data is not automatically available in the MATLAB workspace Instead you must explicitly extract data from the engine using the getdata function Toolbox Components The flow of acquired data consists of these two independent steps 1 Data acquired from the hardware is stored in the engine 2 Data is extracted from the engine and stored in MATLAB or output to a disk file These two steps are illustrated below MATLAB 2 Extract data from the engine Data Acquisition Toolbox Data acquisition engine Acquired data 1 Fill engine with acquired data Hardware lt Sensors 2 5 2 Getting Started with the Data Acquisition Toolbox 2 6 The Flow of Output Data Outputting data means that data is flowing from the data acquisition engine to the hardware device However before data is output you must queue it in the engine with the putdata function The amount of data that you can queue depends on several factors including the available memory the number of hardware channels to which data is output and the size of each
376. ou call M file functions called object creation functions or object constructors These M files are implemented using the object oriented programming capabilities provided by MATLAB which are described in MATLAB Classes and Objects in the Help browser The device object creation functions are listed below Table 3 1 Device Object Creation Functions Function Description analoginput Create an analog input object analogoutput Create an analog output object digitalio Create a digital I O object Before you can create a device object the associated hardware driver adaptor must be registered Adaptor registration occurs automatically However if for some reason an adaptor is not automatically registered then you must do so manually with the daqregister function Refer to Registering the Hardware Driver Adaptor on page A 18 for more information You can find out how to create device objects for a particular vendor and subsystem with the 0bjectConstructorName field of the daqhwinfo function For example to find out how to create an analog input object for an installed National Instruments board you supply the appropriate adaptor name to daqhwinfo out daghwinfo nidaq out ObjectConstructorName ans analoginput nidaq 1 analogoutput nidaq 1 digitalio nidaq 1 Creating a Device Object The constructor syntax tells you that you must supply the adaptor name and the hardware ID t
377. ound addchannel ao 1 You should use manual triggers when starting multiple device objects because this trigger type executes faster than other trigger types with the exception of hardware triggers Additionally to synchronize the input and output of data you should configure the ManualTriggerHwOn property to Trigger for ai set ai ao TriggerType Manual set ai ManualTriggerHwOn Trigger Configure ai for continuous acquisition call the callback function qmoredata whenever 1000 samples are output and call daqcallback when ai and ao stop running set ai SamplesPerTrigger inf set ao SamplesOutputFcn qmoredata ai set ao SamplesOutputFcnCount 1000 set ai ao StopFcn daqcallback As shown below the callback function qmoredata extracts data from the engine and then queues it for output function qmoredata obj event ai data getdata ai 1000 putdata obj data 6 37 6 Analog Output 6 38 Queue data in the engine start the device objects and execute the manual triggers data zeros 4000 1 putdata ao data start ai ao trigger ai ao Note Device objects cannot execute simultaneously unless you use an external hardware trigger You can determine the starting time for each device object with the InitialTriggerTime property The difference in seconds between the starting times for ai and ao is aitime ai InitialTriggerTime aotime ao InitialTrigger
378. ount po HPPEEEP PEPE PEPE PEPE EPEE PEEP EEE EEE EEE EEE ed Vertical PEEP EP EEE EE EEE PEPE PEPE EEE PEEP EEE EEE EEE EEE coo O Type independent CH1 hannel CA0 z Offset Scale ndition Rising z luen p c e tT Ger p Sec CHO 1 0Vidiv 10 0msidiv CH1 1 0Vidiv On Trigger Display panel Channel scaling panel Trigger panel Note that you can also open the Oscilloscope by e Typing softscope without any arguments and using the Hardware Configuration GUI to configure the hardware device e Supplying a configuration file as an input argument to softscope Refer to Saving and Loading the Oscilloscope Configuration on page 9 25 for more information Opening the Oscilloscope Hardware Configuration If you type softscope without supplying an analog input object softscope the Hardware Configuration GUI is opened which allows you to select the hardware device to be used with the Oscilloscope The GUI shown below is configured to display the first two hardware channels of the mcc Demo Board in the Oscilloscope The channels are sampled at a rate of 5000 Hz and use the default input range After you click the OK button the Oscilloscope opens ax Adaptor mcc x ID jo gt ae EN Set the sampling rate ample Rate HZ g to 5000 Hz Input Type Differential x Select the channels to add SelectAll Unselect All H Channel Name Description Input Range CHO Hardware
379. our input lines and four output lines to dio from port 0 addline dio 0 7 in in in in out out out out Suppose you want to add the first two lines from port 0 configured for input and the first two lines from port 2 configured for output There are four ways to do this The first way requires only one call to addline because it uses the hardware line IDs and not the port IDs addline dio 0 1 8 9 in in out out Adding Lines to a Digital I O Object The second way requires two calls to addline and specifies one line ID and multiple port IDs for each call addline dio 0O 0O 2 in out addline dio 1 0 2 in out The third way requires two calls to addline and specifies multiple line IDs and one port ID for each call addline dio 0 1 0 in addline dio 0 1 2 out Lastly you can use four addline calls one for each line added 7 Digital Input Output Writing and Reading Digital I O Line Values After you add lines to a digital I O DIO object you can e Write values to lines e Read values from lines Note Unlike analog input and analog output objects you do not control the behavior of DIO objects by configuring properties This is because buffered DIO is not supported and data is not stored in the engine Instead you either write values directly to or read values directly from the hardware lines Writing Digital Values You write values to
380. ox base properties Presents a complete description of all toolbox device specific properties Presents tips to help you troubleshoot your hardware Describes how to allocate and return memory resources Provides a description of data acquisition terms Installation Information Installation Information To acquire live measured data into the MATLAB environment or to output data from the MATLAB environment you must install these components e MATLAB 6 5 Release 13 e The Data Acquisition Toolbox e A supported data acquisition device for a complete listing of all supported devices visit the Data Acquisition Toolbox section of the MathWorks Web site at http www mathworks com products daq e Software such as drivers and support libraries as required by your data acquisition device Toolbox Installation To determine if the Data Acquisition Toolbox is installed on your system type ver at the MATLAB prompt MATLAB displays information about the versions of MATLAB you are running including a list of installed add on products and their version numbers Check the list to see if the Data Acquisition Toolbox appears For information about installing the toolbox see the MATLAB Installation Guide for your platform If you experience installation difficulties and have Web access look for the license manager and installation information at the MathWorks Web site http www mathworks com Hardware and Drive
381. p Cleaning Up When you no longer need a device object you should clean up the MATLAB environment by removing the object from memory the engine and from the workspace These are the steps you take to end a data acquisition session You remove device objects from memory with the delete function For example to delete the analog input object ai created in the preceding section delete ai A deleted device object is invalid which means that you cannot connect it to the hardware In this case you should remove the object from the MATLAB workspace To remove device objects and other variables from the MATLAB workspace use the clear command clear ai If you use clear on a device object that is connected to hardware the object is removed from the workspace but remains connected to the hardware You can restore cleared device objects to MATLAB with the daqfind function 3 25 3 The Data Acquisition Session 3 26 Getting Started with Analog Input Analog input AI subsystems convert real world analog signals from a sensor into bits that can be read by your computer AI subsystems are typically multichannel devices offering 12 or 16 bits of resolution The Data Acquisition Toolbox provides access to analog input devices through an analog input object The purpose of this chapter is to show you how to perform simple analog input tasks using just a few functions and properties After reading this chapter you should be
382. p get propinfo set 10 39 daqread Purpose Syntax Arguments Description 10 40 Read a Data Acquisition Toolbox daq file data daqread file data daqread file PropertyName PropertyValue data time daqread data time abstime daqread data time abstime events daqread data time abstime events daqinfo daqread daqinfo daqread file info file A Data Acquisition Toolbox daq file PropertyName A daqread property name PropertyValue A daqread property value info Specifies that device object and hardware information are to be returned data An m by n array where m is the number of samples and n is the number of channels time An m by 1 array of relative time values where m is the number of samples abstime The absolute time of the first trigger events A structure containing event information daqinfo A structure containing device object and hardware information data daqread file reads all the data from file data is an m by n data matrix where m is the number of samples and n is the number of channels If data includes data from multiple triggers then m is increased by the number of triggers because of the addition of NaN s daqread data daqread file PropertyName PropertyValue reads the specified data from file The amount of data returned and the format of the data is specified with the properties shown below Pr
383. per second on each channel 8000 samples per trigger on each channel 1 sec of data to be logged per trigger Log data to Memory on trigger Trigger Parameters 1 Manual trigger s on TRIGGER Engine status Waiting for START O samples acquired since starting O samples available for GETDATA AI object contains channel s Index ChannelName HwChannel InputRange SensorRange UnitsRange Units 1 Mono 1 1 1 1 1 1 1 Volts You can use the Channel property to display only the channel summary information AI Channel 4 23 4 Getting Started with Analog Input 4 24 Doing More with Analog Input This chapter presents the complete analog input functionality available to you with the Data Acquisition Toolbox Properties and functions are described in a way that reflects the typical procedures you will use to configure an analog input session The sections are as follows Configuring and Sampling Configure hardware characteristics related to the input channel type Input Channels p 5 2 the sampling rate and the channel skew Managing Acquired Data Preview data and extract data from memory p 5 8 Configuring Analog Input Initiate logging acquired data to memory or to a disk file Triggers p 5 19 Events and Callbacks Enhance your analog input session using events and callbacks p 5 45 Linearly Scaling the Data Configure engineering units properties so that extracted data is Enginee
384. pically used to indicate if time based events are being generated Running is automatically set to Off once the stop function is issued the specified data is acquired or sent or a run time error occurs When Running is Off you cannot acquire or send data However you can acquire one sample with the getsample function or send one sample with the putsamp1le function Characteristics Usage AI AO DIO Common Access Read only Data type String Read only N A when running Values Of fF The device object is not running On The device object is running See Also Functions getsample putsample start Properties Logging Sending 11 61 RuntimeErrorFcn Purpose Description Characteristics Values 11 62 Specify the M file callback function to execute when a run time error occurs A run time error event is generated immediately after a run time error occurs This event executes the callback function specified for RuntimeErrorFcn Additionally a toolbox error message is automatically displayed to the MATLAB workspace If an error occurs that is not explicitly handled by the toolbox then the hardware specific error message is displayed The default value for RunTimeErrorFcn is daqcallback which displays the event type the time the event occurred and the device object name along with the error message Run time error event information is stored in the Type and Data fields of the EventLog property The Type field value i
385. ples When you return data that spans multiple triggers a NaN is inserted in the data stream between trigger events Therefore an extra sample the NaN is stored in the engine and returned by getdata Identifying these NaNs allows you to locate where and when each trigger was issued in the data stream Configuring Analog Input Triggers The figure below illustrates the data stored by the engine during a multiple trigger acquisition The data acquired for each trigger is given by the SamplesPerTrigger property value The relative trigger times are shown on the Time axis where the first trigger time corresponds to t4 0 seconds by definition the second trigger time corresponds to to and so on Logging Trigger 1 Trigger 2 Trigger n SamplesPerTrigger On F Off ty t2 I Data stored in engine The following code modifies daqdoc5_5 so that multiple trigger data is extracted from the engine with one call to getdata returndata ActualRate duration AIVoice TriggerRepeat 1 start AIVoice d t getdata AIVoice returndata Plot the data plot t d xlabel Time sec ylabel Signal Level Volts title Voice Activation for Both Triggers grid on 5 33 5 Doing More with Analog Input The multiple trigger data is shown below Voice Activation for Both Triggers T T T T Signal Level Volts 0 4 1 1 1 1 f f 0 0 2 0 4 0 6 0 8 1 1 2 1 4 Time sec You can find the
386. predefined period of time passes TimerPeriod Specify the period of time between timer events Properties By Category Digital 1 O Common Properties Continued Type Indicate the device object type UserData Store data that you want to associate with a device object Line Properties The digital I O line properties are given below Digital I O Line Properties Direction Specify whether a line is used for input or output HwLine Specify the hardware line ID Index Indicate the MATLAB index of a hardware line LineName Specify a descriptive line name Parent Indicate the parent device object of a line Port Specify the port ID Type Indicate a line 11 13 11 bs Property Referenc Properties Alphabetical List 11 14 This section contains detailed descriptions of all toolbox device specific properties Each property reference page contains some or all of this information e The property name e A description of the property e The property characteristics including Usage the device objects the property can be used with and whether it is acommon property or a channel or line property Common properties apply to all channels or lines contained by the device object while channel line properties can be set on a per channel per line basis The device objects supported by the Data Acquisition Toolbox include analog input AD analog output AO and digital I O DIO objects
387. put mode Al InputSource Specify the input to the A D converter Al 12 3 12 Device Specific Property Reference Property Name Description Device Objects RampRate Specify the source ramp up and ramp down AO rate SourceMode Specify the source mode AO SourceOutput Specify the source output AO Span Specify the measurement bandwidth in Hz AI AO Sum Specify whether the source sum input is AO enabled or disabled Keithley Properties The device specific Keithley properties for analog input AI and analog output AO objects are given below Property Name Description Device Objects OutOfDataMode Specify how the value held by the analog AO output subsystem is determined StopTrigger Specify the analog input channel serving as AI Channel a hardware stop trigger source StopTrigger Specify the condition that must be satisfied AI AO Condition before a stop trigger executes StopTrigger Specify a value for the stop trigger condition AI ConditionValue StopTrigger Specify the delay value for a stop trigger Al Delay StopTrigger Specify the units in which the stop trigger AI DelayUnits delay is measured 12 4 Properties By Vendor Property Name Description Device Objects StopTrigger Specify the type of stop trigger to execute AI Type TransferMode Specify how data is transferred from the AI AO data acquisition device to system memory Measurement Computing Properti
388. put mode for all channels within the device to change If there is a smart break out box present then you can set the input mode on a per channel basis Vendor Agilent Technologies Usage AI Channel Access Read write Data Type String Read only Yes when running InputMode Values Voltage The input mode is set to volts ICP The input mode is set to ICP Charge The input mode is set to charge amp Mic The input mode is set to microphone 200VoltMic The input mode is set to microphone with 200 volt supply turned on See Also Properties Coupling InputRange InputType 12 15 InputSource Purpose Specify the input to the A D converter Description For input channels InputSource can be SwitchBox CALIN Ground and BOBCALIN The BOBCALIN value is valid only when a smart break out box BoB is connected to the input Smart BoB s include a charge break out box or a microphone break out box When a smart break out box is attached to an E1432 or E1433 module additional input modes are available These additional input modes are available through the InputMode property After a hardware reset InputSource is automatically set to SwitchBox Characteristics Vendor Usage Access Data Type Read only when running Values SwitchBox CALIN Ground BOBCALIN See Also Properties InputMode 12 16 Agilent Technologies AI Channel Read write String Yes Select the front panel connector Select the module s
389. qhwinfo Purpose Syntax Arguments Description 10 32 Display data acquisition hardware information out daghwinfo out daqhwinfo adaptor out daqhwinfo obj out daqhwinfo obj FieldName adaptor The hardware driver adaptor name The supported adaptors are hpe1432 keithley mcc nidaq parallel and winsound obj A device object or array of device objects FieldName A single field name or a cell array of field names out A structure containing the requested hardware information out daghwinfo returns general hardware related information as a structure to out The returned information includes installed adaptors the toolbox and MATLAB version and the toolbox name out dagqhwinfo adaptor returns hardware related information for the specified adaptor The returned information includes the adaptor DLL name the board names and IDs and the device object constructor syntax out daghwinfo adaptor FieldName returns the hardware related information specified by FieldName for adaptor FieldName must be a single string out is a cell array You can return a list of valid field names with the daqhwinfo adaptor syntax out daghwinfo obj returns hardware related information for the device object obj If obj is an array of device objects then out is a 1 by n cell array of structures where n is the length of obj The returned information depends on the device object type and might inclu
390. qpropedit 10 38 daqread 10 40 daqregister 10 44 daqreset 10 45 daqschool 10 46 Index dec2binvec 10 47 delete 10 49 digitalio 10 51 disp 10 53 flushdata 10 55 get 10 57 getdata 10 59 getsample 10 63 getvalue 10 64 ischannel 10 65 isdioline 10 66 isvalid 10 67 length 10 69 load 10 71 makenames 10 73 muxchanidx 10 74 obj2mfile 10 76 peekdata 10 78 propinfo 10 80 putdata 10 82 putsample 10 84 putvalue 10 85 save 10 86 set 10 87 setverify 10 90 showdagevents 10 92 size 10 94 softscope 10 96 start 10 104 stop 10 105 trigger 10 107 waittilstop 10 108 gain 1 21 engineering units AI 5 55 gain list 4 4 get function 10 57 getdata function 10 59 getsample function 10 63 getvalue function 10 64 graphical property editor 3 20 grounded signal 1 23 GroundingMode property 12 13 GUI Channel Editor Channel Display pane 9 5 Channel pane 9 7 Channel Properties pane 9 13 Channel Exporter 9 23 Hardware Configuration 9 3 Measurement Editor Measurement pane 9 18 Measurement Properties pane 9 22 Measurement Exporter 9 24 Oscilloscope 9 2 Property Editor 3 21 Scope Editor Scope pane 9 5 Scope Properties pane 9 12 H hardware initializing 10 45 resources 2 17 scanning 1 16 setting up 1 3 simultaneous sample and hold 1 18 supported vendors 2 7 hardware channels Oscilloscope 9 2 Hardware Configuration GUI 9 3 1 7 Index hardware ID channel 4 3 device board 4 2 line 7 4 mapping to channels 3 9 port
391. r Installation Installation of your hardware device hardware drivers and any other device specific software is described in the documentation provided by your hardware vendor Note You need to install all necessary device specific software provided by your hardware vendor in addition to the Data Acquisition Toolbox xvii Preface Typographical Conventions This manual uses some or all of these conventions ltem Convention Example Example code Function names syntax filenames directory folder names user input items in drop down lists Buttons and keys Literal strings in syntax descriptions in reference chapters Mathematical expressions MATLAB output Menu and dialog box titles New terms and for emphasis Omitted input arguments String variables from a finite list Monospace font Monospace font Boldface with book title caps Monospace bold for literals Italics for variables Standard text font for functions operators and constants Monospace font Boldface with book title caps Italics ellipsis denotes all of the input output arguments from preceding syntaxes Monospace italics To assign the value 5 to A enter A 5 The cos function finds the cosine of each array element Syntax line example is MLGetVar ML_var_name Press the Enter key f freqspace n whole This vector represents the polynomial p x 2x 3 MATLAB resp
392. r a trigger occurs You can log data either before the trigger or after the trigger Logging data before the trigger occurs is called pretriggering while logging data after a trigger occurs is called posttriggering You configure trigger delays with the TriggerDelay property Pretriggers are specified by a negative TriggerDelay value while posttriggers are specified by a positive TriggerDelay value You can delay data logging in time or in samples using the TriggerDelayUnits property When TriggerDelayUnits is set to Samples data logging is delayed by the specified number of samples When the TriggerDelayUnits property is set to Seconds data logging is delayed by the specified number of seconds 5 25 5 Doing More with Analog Input 5 26 Capturing Pretrigger Data In some circumstances you might want to capture data before the trigger occurs Such data is called pretrigger data When capturing pretrigger data the SamplesPerTrigger property value includes the data captured before and after the trigger occurs Capturing pretrigger data is illustrated below i Pretrigger samples Trigger samples Trigger occurs k SamplesPerTrigger i I Data stored in engine You can capture pretrigger data for manual triggers and software triggers If TriggerType is Manual and the trigger function is issued before the trigger delay passes then a warning is returned and the trigger is ignored the trigger event does not occur
393. rdware information by specifying the appropriate arguments to daqread For example to retrieve all event information you must return all the logged data data time abstime events info daqread file00 daq events Type ans Start Trigger Trigger Trigger Trigger Stop If you retrieve part of the data then only the events associated with the requested data are returned data time abstime events info daqread file00 daq Trigger 1 3 events Type ans Trigger Trigger Trigger You can retrieve the entire event log as well as object and hardware information by including info as an input argument to daqread daqinfo daqread file00 daq info daqinfo ObjInfo 1x1 struct HwInfo 1x1 struct To return the event log information eventinfo daqinfo 0bjInfo EventLog eventinfo 6x1 struct array with fields Type Data softscope The Data Acquisition Oscilloscope The data acquisition Oscilloscope is an interactive graphical user interface GUI for streaming data into a display The sections are as follows Opening the Oscilloscope Associate hardware with the Oscilloscope and open the application p 9 2 Displaying Channels p 9 4 Display hardware math and reference channels Scaling the Channel Data Scale channel data horizontally and vertically p 9 11 Triggering the Oscilloscope Control how the data acquisition is initiated p 9 14 Making Measurements M
394. re sampling at 30 Hz Aliasing occurs when the sampled signal contains frequency components greater than one half the sampling rate The frequency components could originate from the signal of interest in which case you are undersampling and should increase the sampling rate The frequency components could also originate from noise in which case you might need to condition the signal using a filter The rule used to prevent aliasing is given by the Nyquist theorem which states that e An analog signal can be uniquely reconstructed without error from samples taken at equal time intervals e The sampling rate must be equal to or greater than twice the highest frequency component in the analog signal A frequency of one half the sampling rate is called the Nyquist frequency However if your input signal is corrupted by noise then aliasing can still occur For example suppose you configure your A D converter to sample at a rate of 4 samples per second 4 S s or 4 Hz and the signal of interest is a 1 Hz sine wave Because the signal frequency is one fourth the sampling rate then according to the Nyquist theorem it should be completely characterized Making Quality Measurements However if a 5 Hz sine wave is also present then these two signals cannot be distinguished In other words the 1 Hz sine wave produces the same samples as the 5 Hz sine wave when the sampling rate is 4 S s This situation is shown below
395. re and the DMA controller moves the data directly into memory 3 The DMA controller gets ready for the next sample by pointing to the next open memory location 4 The previous steps are repeated indefinitely with data going to each open memory location in a continuously circulating buffer No interaction between the CPU and the board is needed Your computer supports several different DMA channels Depending on your application you can use one or more of these channels For example simultaneous input and output with a sound card requires one DMA channel for the input and another DMA channel for the output 1 27 T introduction to Data Acquisition 1 28 Making Quality Measurements For most data acquisition applications you need to measure the signal produced by a sensor at a specific rate In many cases the sensor signal is a voltage level that is proportional to the physical phenomena of interest for example temperature pressure or acceleration If you are measuring slowly changing quasi static phenomena like temperature a slow sampling rate usually suffices If you are measuring rapidly changing dynamic phenomena like vibration or acoustic measurements a fast sampling rate is required To make high quality measurements you should follow these rules e Maximize the precision and accuracy e Minimize the noise e Match the sensor range to the A D range Accuracy and Precision Whenever you acquire measured d
396. re devices contain one or more subsystems that convert digitize real world sensor signals into numbers your computer can read Such devices are called analog input subsystems AI subsystems A D converters or ADCs After the real world signal is digitized you can analyze it store it in system memory or store it to a disk file The function of the analog input subsystem is to sample and quantize the analog signal using one or more channels You can think of a channel as a path through which the sensor signal travels Typical analog input subsystems have eight or 16 input channels available to you After data is sampled and quantized it must be transferred to system memory Analog signals are continuous in time and in amplitude within predefined limits Sampling takes a snapshot of the signal at discrete times while quantization divides the voltage or current value into discrete amplitudes Sampling quantization channel configuration and transferring data from hardware to system memory are discussed below Sampling Sampling takes a snapshot of the sensor signal at discrete times For most applications the time interval between samples is kept constant for example sample every millisecond unless externally clocked For most digital converters sampling is performed by a sample and hold S H circuit An S H circuit usually consists of a signal buffer followed by an electronic switch connected to a capacitor The operation o
397. red for either input or output You read values from an input line and write values to an output line Whether a given hardware line is addressable for input or output depends on the port it resides on You can classify digital I O ports into these two groups based on your ability to address lines individually e Port configurable devices You cannot address the lines associated with a port configurable device individually Therefore you must configure all the 7 5 7 Digital Input Output 7 6 lines for either input or output If you attempt to mix the two configurations an error is returned You can add any number of available port configurable lines to a DIO object However the engine will address all lines behind the scenes For example if one line is added to a DIO object then you automatically get all lines Therefore if a DIO object contains lines from a port configurable device and you write a value to one or more of those lines then all the lines are written to even if they are not contained by the device object e Line configurable devices You can address the lines associated with a line configurable device individually Therefore you can configure individual lines for either input or output Additionally you can read and write values on a line by line basis Note that for National Instruments E Series hardware port 0 is always line configurable while all other ports are port configurable You can return the
398. rement panel and trigger panel in the Oscilloscope at a time e Scope Properties Configure properties for the displays the channel panel the measurement panel and the trigger panel Scope Editor 3 xj Scope Properties Define a new display Label l Add Defined scope components Channel Scaling Measurements Triggers _ display Delete OK Cancel Apply Help 10 101 softscope 10 102 Channel Editor The Channel Editor consists of three panes e Channel Add or delete math channels and reference channels and select which defined channels are available to the Oscilloscope e Channel Properties Configure properties for defined hardware channels math channels and reference channels e Channel Display Select the Oscilloscope display for each defined channel or choose to not display a channel Channel Editor Exi i Channel Properties Channel Display Define a new channel Type math x Name ee Expression Co Display aisplayt x Add Defined channels a Type _Name Data Source Display M Hardware CH1 Hardware Channel display M Hardware CH2 Hardware Channel display1 Delete OK Cancel Apply Help softscope Measurement Editor The Measurement Editor consists of three panes e Measurement Add or delete measurements and select which defined measureme
399. rify ai SampleRate 48000 Functions propinfo setverify Properties ChannelSkew 11 65 SamplesAcquired Purpose Description Characteristics Values See Also 11 66 Indicate the number of samples acquired per channel SamplesAcquired is continuously updated to reflect the current number of samples acquired by an analog input object It is reset to zero after a start function is issued Use the SamplesAvailable property to find out how many samples are available to be extracted from the engine Usage AI Common Access Read only Data type Double Read only N A when running The value is continuously updated to reflect the current number of samples acquired The default value is zero Functions start Properties SamplesAvailable SamplesAcquiredFcn Purpose Specify the M file callback function to execute every time a predefined number of samples is acquired for each channel group member Description A samples acquired event is generated immediately after the number of samples specified by the SamplesAcquiredFcnCount property is acquired for each channel group member This event executes the callback function specified for SamplesAcquiredFcn You should use SamplesAcquiredFcn if you must access each sample that is acquired If you do not have this requirement you might want to use the TimerFcn property Samples acquired event information is not stored in the EventLog property Characteristics
400. ring Units p 5 55 linearly scaled 5 Doing More with Analog Input Configuring and Sampling Input Channels The hardware you are using has characteristics that satisfy your specific application needs Some of the most important hardware characteristics are related to configuring e The input channel type e The sampling rate e The channel skew scanning hardware only Properties associated with configuring and sampling input channels are given below Table 5 1 Analog Input Properties Related to Sampling Channels Property Name Description ChannelSkew Specify the time between consecutive scanned hardware channels ChannelSkewMode Specify how the channel skew is determined InputType Specify the analog input hardware channel configuration SampleRate Specify the per channel rate at which analog data is converted to digital data 5 2 Configuring and Sampling Input Channels Input Channel Configuration You can configure your hardware input channels with the InputType property The device specific values for this property are given below Table 5 2 InputType Property Values Vendor InputType Value Agilent Technologies Differential Keithley Differential SingleEnded Measurement Computing Differential SingleEnded National Instruments Differential SingleEnded NonReferencedSingleEnded Sound Cards AC Coupled The InputType value determines the number of hardware channels you can a
401. ringMode property is set to Auto and the MaxSamplesQueued property might not be restored to the same value because both these property values are based on available memory Note load is not used to read in acquired data that has been saved to a log file You should use the daqread function for this purpose If you use the help command to display the M file help for load then you must supply the pathname shown below help daq private load This example illustrates the behavior of load when the loaded device object has properties that differ from the workspace object ai analoginput winsound addchannel ai 1 2 save ai ai SampleRate 10000 load ai Warning Loaded object has updated property values Functions daqread propinfo save makenames Purpose Syntax Arguments Description Remarks Example See Also Generate a list of descriptive channel or line names names makenames prefix index prefix A string that constitutes the first part of the name index Numbers appended to the end of prefix any MATLAB vector syntax can be used to specify index as long as the numbers are positive names An m by 1 cell array of channel names where m is the length of index names makenames prefix index generates a cell array of descriptive channel or line names by concatenating prefix and index You can pass names as an input argument to the addchannel or addline function If name
402. rom memory and from the MATLAB workspace delete ai clear ai Outputting Data If you have a sound card installed you can run the following example which outputs 1 second of data to two analog output hardware channels You should modify this example to suit your specific application needs If you want detailed information about outputting data refer to Chapter 6 Analog Output 1 Create a device object Create the analog output object ao for a sound card ao analogoutput winsound 2 Add channels Add two hardware channels to ao addchannel ao 1 2 3 Configure property values Configure the sampling rate to 44 1 kHz for each channel set ao SampleRate 44100 2 9 2 Getting Started with the Data Acquisition Toolbox 2 10 4 Output data Create 1 second of output data and queue the data in the engine for eventual output to the analog output subsystem You must queue one column of data for each hardware channel added data sin linspace 0 2 pi 500 44100 putdata ao data data Start the output When all the data is output ao automatically stops executing start ao Clean up When you no longer need ao you should remove it from memory and from the MATLAB workspace delete ao clear ao Reading and Writing Digital Values If you have a supported National Instruments board with at least eight digital I O lines you can run the following example which outputs digital
403. roperty default value ReadOnly If the property is read only a 1 is returned Otherwise a 0 is returned ReadOnlyRunning Ifthe property is read only while the device object is running a 1 is returned Otherwise a 0 is returned DeviceSpecific If the property is device specific a 1 is returned If a 0 is returned the property is supported for all device objects of a given type 2 21 2 Getting Started with the Data Acquisition Toolbox For example to return the characteristics for all the properties associated with the analog input object ai created in the preceding section Alinfo propinfo ai The characteristics for the TriggerType property are displayed below Alinfo TriggerType ans Type string Constraint Enum ConstraintValue 3x1 cell DefaultValue Immediate ReadOnly 0 ReadOnlyRunning 1 DeviceSpecific 0 This information tells you that e The property value data type is a string e The property value is constrained as an enumerated list of values e There are three possible property values e The default value is Immediate e The property is not read only e You cannot configure the property while the device object is running e The property is supported for all analog input objects To display the property value constraints Alinfo TriggerType ConstraintValue ans Manual Immediate Software 2 22 The Data Acquisition Session The data acquisition se
404. ropinfo function For example suppose you create the analog input object ai for a sound card and you want to find the default value for the SampleRate property ai analoginput winsound out propinfo ai SampleRate out DefaultValue ans 8000 Properties By Category Properties By Category This section contains brief descriptions of all toolbox base properties The properties are categorized according to these subsystems e Analog input properties e Analog output properties e Digital I O properties Depending on the hardware device you are using additional property names or property values might be present The additional property names are described in Chapter 12 Device Specific Property Reference For example only analog input and analog output objects associated with a sound card have a BitsPerSample property The additional property values are also device specific but are included in this chapter For example all supported devices have an InputType property but the value AC Coupled is unique to analog input objects associated with a sound card Analog Input Properties Analog input base properties are divided into two main categories common properties and channel properties Common properties apply to every channel contained by the analog input object while channel properties can be configured for individual channels Common Properties The analog input common properties are grouped into the fol
405. ror is returned e Ifthe requested data is not returned in the expected amount of time an error is returned The expected time to return data is given by the time it takes the engine to fill one data block plus the time specified by the Timeout property e You can issue C Control C while getdata is blocking This will not stop the acquisition but will return control to MATLAB e The SamplesAcquired property keeps a running count of the total number of samples per channel that have been acquired e The SamplesAvailable property tells you how many samples you can extract from the engine per channel e MATLAB supports math operations only for the double data type Therefore if you extract data using the native data type of your hardware typically int16 you must convert the data to doubles before performing math operations For more information about getdata refer to its reference pages in Chapter 10 Function Reference Example Previewing and Extracting Data Suppose you have a data acquisition application that is particularly time consuming By previewing the data you can ascertain whether the acquisition is proceeding as expected without acquiring all the data If it is not then you can abort the session and diagnose the problem This example illustrates how you might use peekdata and getdata together in such an application You can run this example by typing daqdoc5 2 at the MATLAB command line 1 Create a device obj
406. rovides toolbox specific implementations of these functions using the same function name To get command line help for an overloaded toolbox function using the help command you must supply one of two possible class directories to help help daqdevice function_name help daqchild function_name Note that the same help information is returned regardless of the class directory specified For example the Data Acquisition Toolbox provides an overloaded version of the delete function To obtain help for the MATLAB version of this function type help delete You can determine if a function is overloaded by examining the last section of the help For delete the help contains the following overloaded versions not all are shown Overloaded methods help char delete m help scribehandle delete m help daqdevice delete m help daqchild delete m So to obtain help on the toolbox version of this function type help daqdevice delete For more information on overloaded functions and class directories refer to MATLAB Classes and Objects in the Help browser 10 2 Functions By Category Functions By Category This section contains brief descriptions of all toolbox functions The functions and the device objects they are associated with are categorized according to usage The supported device objects include analog input AI analog output AO and digital I O DIO A number of other MATLAB M file helper functions are prov
407. rpose Specify if AISENSE is driven to onboard ground Purpose DriveAISenseToGround can be On or Off If DriveAISenseToGround is Off then AISENSE is not driven to onboard ground If DriveAISenseToGround is On then AISENSE is driven to onboard ground AISENSE serves as the hardware reference node when channels are configured in nonreferenced single ended NRSE mode Channels are configured with the InputType property If InputType is NonReferencedSingleEnded then the hardware device uses AISENSE for the negative input of the amplifier regardless of the DriveAISenseToGround value If InputType is Differential or SingleEnded then the hardware device drives AISENSE to onboard ground only if DriveAISenseToGround is On Characteristics Vendor National Instruments Usage AI Common Access Read write Data type String Read only Yes when running Values Off Do not drive AISENSE to onboard ground On Drive AISENSE to onboard ground See Also Properties InputType 12 12 GroundingMode Purpose Description Characteristics Values Specify the input channel grounding mode GroundingMode can be Grounded or Floating If GroundingMode is Grounded the low side of the channel is grounded If GroundingMode is Floating the low side of the channel floats thereby making the input a differential input GroundingMode can be set only for input channels Source channels are never floating and are always grounded If a smart break out box
408. rt hwinfo Port 2 ans ID 1 LineIDs 0 1 2 3 4 Direction in Config port 7 8 Adding Lines to a Digital I O Object hwinfo Port 3 ans ID 2 LineIDs 0 1 2 3 Direction in out Config port This information tells you that all 17 lines are port configurable you can input and output values using the 12 lines associated with ports 0 and 2 and that you can only input values from the five lines associated with port 1 For easy reference the LineName property is automatically populated with a name that includes the port pin number Referencing Individual Hardware Lines As described in the preceding section you can access lines with the Line property or with a line object To reference individual lines you must specify either MATLAB indices or descriptive line names MATLAB Indices Every hardware line contained by a DIO object has an associated MATLAB index that is used to reference the line When adding lines with the addline function index assignments are made automatically The line indices start at 1 and increase monotonically up to the number of line group members The first line indexed in the line group represents the least significant bit LSB and the highest indexed line represents the most significant bit MSB Unlike adding channels with the addchannel function you cannot manually assign line indices with addline For example the digital I O object dio created in the prec
409. rties and channel properties Common properties apply to all channels contained by the device object while channel properties apply to individual channels The properties you configure depend on your particular analog output application For many common applications there is a small group of properties related to the basic setup that you will typically use These basic setup properties control the sampling rate and define the trigger type Analog output properties related to the basic setup are given below Table 6 3 Analog Output Basic Setup Properties Property Name Description SampleRate Specify the per channel rate at which digital data is converted to analog data TriggerType Specify the type of trigger to execute Setting the Sampling Rate You control the rate at which an analog output subsystem converts digital data to analog data is controlled with the SampleRate property SampleRate must be specified as samples per second For example to set the sampling rate for each channel of your National Instruments board to 100 000 samples per second 100 kHz ao analogoutput nidaq 1 addchannel ao 0 1 set ao SampleRate 100000 6 5 6 Analog Output 6 6 Data acquisition boards typically have predefined sampling rates that you can set If you specify a sampling rate that does not match one of these predefined values there are two possibilities e Ifthe rate is within the range of valid values then t
410. s subplot 211 plot data xlabel Samples ylabel Signal Volts subplot 212 plot time data xlabel Time seconds ylabel Signal Volts Alternatively you can retrieve data for the second sound card channel by specifying the channel name data time daqread file00 daq Samples 1000 2000 Channels Right Retrieving Data Based on Triggers You can retrieve data based on triggers using the Triggers property To retrieve all the data associated with the second and third triggers for both sound card channels data time daqread file00 daq Triggers 2 3 Plot the data and label the figure axes subplot 211 plot data xlabel Samples ylabel Signal Volts subplot 212 plot time data xlabel Time seconds ylabel Signal Volts Retrieving Data Based on Time You can retrieve data based on time using the Time property Time must be specified in seconds and Time 0 corresponds to the first logged sample To retrieve the first 25 of the data acquired for the first trigger data time daqread file00 daq Time 0O 0 5 Plot the data and label the figure axes subplot 211 plot data xlabel Samples ylabel Signal Volts subplot 212 plot time data xlabel Time seconds ylabel Signal Volts 8 Saving and Loading the Session Retrieving Event Object Channel and Hardware Information You can retrieve event object channel and ha
411. s InstaCal daqhwinfo will return this configuration information For example if you configure your Measurement Computing device for 16 single ended channels using InstaCal daqhwinfo returns this configuration However the toolbox does not preserve configuration information that is not directly associated with your hardware For example channel name information is not preserved Refer to Appendix A Troubleshooting Your Hardware for more information about using vendor tools General Toolbox Information To display general information about the Data Acquisition Toolbox out daghwinfo out ToolboxName Data Acquisition Toolbox ToolboxVersion 2 2 R13 MATLABVersion 6 5 R13 InstalledAdaptors 4x1 cell The InstalledAdaptors field lists the hardware driver adaptors installed on your system To display the installed adaptors out InstalledAdaptors ans mcc nidaq parallel winsound 2 Getting Started with the Data Acquisition Toolbox 2 18 This information tells you that an adaptor is available for Measurement Computing and National Instruments devices parallel ports and sound cards Note The list of installed adaptors might be different for you platform Toolbox adaptors are available to you only if the associated hardware driver is installed Adaptor Specific Information To display hardware information for a particular vendor you must supply the adaptor name as an argument
412. s Error The Data field values are given below Data Field Value Description AbsTime The absolute time as a clock vector the event occurred RelSample The acquired AI or output AO sample number when the event occurred String The descriptive error message Run time errors include hardware errors and timeouts Run time errors do not include configuration errors such as setting an invalid property value Usage AI AO Common Access Read write Data type String Read only No when running The default value is daqcallback RuntimeeErrorFcn See Also Functions daqcallback Properties EventLog Timeout 11 63 SampleRate Purpose Description Characteristics Values 11 64 Specify the per channel rate at which analog data is converted to digital data or digital data is converted to analog data SampleRate specifies the per channel rate in samples second that an analog input AI or analog output AO subsystem converts data AI subsystems convert analog data to digital data while AO subsystems convert digital data to analog data AI and AO subsystems have a finite though often large number of valid sampling rates If you specify a sampling rate that does not match one of the valid values then the data acquisition engine automatically selects the next highest supported sampling rate that is within 1 of the requested rate If there is no valid sampling rate within this tolerance the nex
413. s contains more than one descriptive name then the size of names must agree with the number of hardware channels specified in addchannel1 or the number of hardware lines specified in addline If the channels or lines are to be referenced by name then prefix must begin with a letter and contain only letters numbers and underscores Otherwise the names can contain any character Create the analog input object AI You can use makenames to define descriptive names for each channel that is to be added to AI AI analoginput nidaq 1 names makenames chan 1 8 names is an eight element cell array of channel names chan1 chand2 chan8 You can now pass names as an input argument to the addchannel function addchannel AI 0 7 names Functions addchannel addline 10 73 muxchanidx Purpose Syntax Arguments Description Remarks 10 74 Return multiplexed scanned channel index scanidx muxchanidx obj muxboard muxidx scanidx muxchanidx obj absmuxidx obj An analog input object associated with a National Instruments board muxboard The multiplexer board mux idx The index number of the multiplexed channel absmuxidx The absolute index number of the multiplexed channel scanidx The scanning index number of the multiplexed channel scanidx muxchanidx obj muxboard muxidx returns the scanning index number of the multiplexed channel specified by muxidx The multiplexer mux board is specified
414. s digital audio data to analog audio data Therefore the CD sends analog data to the sound card 4 After recording the audio data save it to disk The data is automatically saved as a WAV file 5 Play the saved WAV file While playing the green line in the Sound Recorder should indicate that data is being captured If this is the case then the analog output subsystem on your sound card is functioning properly If you are not able to record or play data make sure that the sound card and input devices are enabled for recording and playback as described in the beginning of this section Sound Cards Running in Full Duplex Mode The term full duplex refers to a system that can send and receive information simultaneously For sound cards full duplex means that the device can acquire input data via an analog input subsystem while outputting data via an analog output subsystem at the same time Note that full tells you nothing about the bit resolution or the number of channels used in each direction Therefore sound cards can simultaneously receive and send data using 8 or 16 bits while in mono or stereo mode A common restriction of full duplex mode is that both subsystems must be configured for the same sampling rate If you try to run your card in full duplex mode and the following error is returned Error using gt daqdevice start Device Winsound already in use then your sound card is not configured properly it
415. s specified by hwline from the port specified by port to the digital T O object obj direction configures the lines for either input or output names is a descriptive line name or cell array of descriptive line names 10 13 addline Remarks 10 14 Rules for Adding Lines e The numeric values you supply for hwline depend on the hardware you access For National Instruments and Measurement Computing hardware line IDs are zero based begin at zero e You can add a line only once to a given digital I O object e Hardware line IDs are stored in the HwLine property and the associated MATLAB indices are stored in the Index property e For a single call to addline you can add multiple lines from one port or the same line ID from multiple ports You cannot add multiple lines from multiple ports e Ifa port ID is not explicitly referenced lines are added first from port 0 then from port 1 and so on e You can specify the line directions as a single value or a cell array of values If a single direction is specified then all added lines have that direction If supported by the hardware you can configure individual lines by supplying a cell array of directions More About MATLAB Indices Every hardware line contained by a device object has an associated MATLAB index that is used to reference the line Index assignments are made automatically by addline and follow these rules e If no hardware lines are contained by the d
416. s such as temperature This is in addition to any built in multiplexing on the DAQ board The A D converter samples one channel switches to the next channel and samples it switches to the next channel and so on Because the same A D converter is sampling many channels the effective sampling rate of each individual channel is inversely proportional to the number of channels sampled You must take care when using multiplexers so that the switched signal has sufficient time to settle Refer to Noise on page 1 32 for more information about settling time T introduction to Data Acquisition Excitation Source Some sensors require an excitation source to operate For example strain gauges and resistive temperature devices RTDs require external voltage or current excitation Signal conditioning modules for these sensors usually provide the necessary excitation RTD measurements are usually made with a current source that converts the variation in resistance to a measurable voltage The Computer The computer provides a processor a system clock a bus to transfer data and memory and disk space to store data The processor controls how fast data is accepted by the converter The system clock provides time information about the acquired data Knowing that you recorded a sensor reading is generally not enough You also need to know when that measurement occurred Data is transferred from the hardware to system memory via dynamic me
417. s these values You can use the get function to return one or more properties and their current values to a variable or to the command line The syntax used to return common and channel line properties is described below The examples are based on the analog input object ai created for a sound card and containing two channels ai analoginput winsound addchannel ai 1 2 Common Properties To return all configurable common property names and their possible values for a device object you must supply the device object to set For example all configurable common properties for ai are shown below The base properties are listed first followed by the device specific properties set ai Buf feringConfig BufferingMode Auto Manual Channel ChannelSkew ChannelSkewMode None ClockSource Internal DataMissedFcn InputOverRangeFcn InputType AC Coupled LogFileName LoggingMode Disk Memory Disk amp Memory LogToDiskMode Overwrite Index ManualTriggerHwOn Start Trigger Name RuntimeErrorFcn SampleRate SamplesAcquiredFcn SamplesAcquiredFcnCount SamplesPerTrigger Configuring and Returning Properties StartFen StopFcn Tag Timeout TimerFcn TimerPeriod TriggerFecn TriggerChannel TriggerCondition None TriggerConditionValue TriggerDelay TriggerDelayUnits Seconds Samples TriggerRepeat TriggerType Manual Immediate Software UserData WINSO
418. sPerSample Purpose Description Characteristics Values Specify the number of bits the sound card uses to represent each sample BitsPerSample can be 8 16 or any value between 17 and 32 The specified number of bits determines the number of unique values a sample can take on For example if BitsPerSamp1e is 8 the sound card represents each sample with 8 bits This means that each sample is represented by a number between 0 and 255 If BitsPerSamp1e is 16 the sound card represents each sample with 16 bits This means that each sample is represented by a number between 0 and 65 535 For older Sound Blaster cards configured for full duplex operation you might not be able to set BitsPerSamp1e to 16 bits for both the analog input and analog output subsystems Instead you need to set one subsystem for 8 bits and the other subsystem for 16 bits Note To use the high resolution greater than 16 bit capabilities for some sound cards you might need to configure BitsPerSample to either 24 or 32 even if your device does not use that number of bits Vendor Usage Access Data type Read only when running 8 16 or 17 32 Sound cards AI AO Common Read write Double Yes Represent data with the specified number of bits 12 9 COLA Purpose Description Characteristics Values 12 10 Specify whether the source constant level output is enabled or disabled COLA can be Off or On If COLA is Off
419. section e Duration How long do you want to sample the signal for If you are storing data to memory or to a disk file then the duration determines the storage resources required The format of the stored data also affects the amount of storage space required For example data stored in ASCII format takes more space than data stored in binary format Sensor Bandwidth In a real world data acquisition experiment the physical phenomena you are measuring has expected limits For example the temperature of your automobile s cooling system varies continuously between its low limit and high limit The temperature limits as well as how rapidly the temperature varies between the limits depends on several factors including your driving habits the weather and the condition of the cooling system The expected limits might be readily approximated but there are an infinite number of possible temperatures that you can measure at a given time As explained in Quantization on page 1 19 these unlimited possibilities are mapped to a finite set of values by your data acquisition hardware 1 9 T introduction to Data Acquisition The bandwidth is given by the range of frequencies present in the signal being measured You can also think of bandwidth as being related to the rate of change of the signal A slowly varying signal has a low bandwidth while a rapidly varying signal has a high bandwidth To properly measure the physical phenomena
420. set to the corresponding range in g s InputRange is set to the value that most closely encompasses the expected data range of 200 mV set chan SensorRange 5 5 set chan InputRange 0 5 0 5 set chan UnitsRange 50 50 set chan Units g s 1g 9 80 m s s 4 Acquire data Start the acquisition start AI 5 57 5 Doing More with Analog Input 5 58 Extract and plot all the acquired data data getdata AI subplot 2 1 1 plot data Calculate and display the frequency information Fs ActualRate blocksize duration ActualRate f mag daqdocfft data Fs blocksize subplot 2 1 2 plot f mag Make sure AI has stopped running before cleaning up the workspace waittilstop AI 2 Clean up When you no longer need AI you should remove it from memory and from the MATLAB workspace delete AI clear AI Analog Output Analog output subsystems convert digital data stored on your computer to a real world analog signal Typical plug in acquisition boards offer two output channels with 12 bits of resolution with special hardware available to support multiple channel analog output operations The Data Acquisition Toolbox provides access to analog output subsystems through an analog output object The purpose of this chapter is to show you how to perform data acquisition tasks using your analog output hardware The sections are as follows Getting Started with Analog Perform basic t
421. some vendors ChannelSkewMode is automatically set to Manual if you first set ChannelSkew to a valid value Usage AI Common Access Read write depends on ChannelSkewMode value Data type Double Read only Yes when running For SS H hardware the only valid value is zero For scanning hardware the value depends on ChannelSkewMode ChannelSkew is specified in seconds Properties ChannelSkewMode 11 21 ChannelSkewMode Purpose Description Characteristics 11 22 Specify how the channel skew is determined For simultaneous sample and hold SS H hardware ChannelSkewMode is None For scanning hardware ChannelSkewMode can be Minimum Equisample or Manual Keithley and National Instruments only SS H hardware includes Agilent Technologies devices and sound cards while scanning hardware includes most Measurement Computing Keithley and NI boards Note that some supported boards from these vendors are SS H such as ComputerBoard s DAS4020 12 If ChannelSkewMode is Minimum then the minimum channel skew supported by the hardware is used Some vendors refer to this as burst mode If ChannelSkewMode is Equisample the channel skew is given by sampling rate number of channels If ChannelSkewMode is Manual then you must specify the channel skew with the ChannelSkew property For some vendors ChannelSkewMode is automatically set to Manual if you first set ChannelSkew to a valid value Note If you want to use th
422. ss than the specified low value with hysteresis given by the specified high value HighHysteresis The trigger occurs when the analog signal is greater than the specified high value with hysteresis given by the specified low value See Also Properties TriggerChannel TriggerConditionValue TriggerType 11 89 TriggerConditionValue Purpose Description Characteristics Values Example See Also 11 90 Specify one or more voltage values that must be satisfied before a trigger executes TriggerConditionValue is used when TriggerType is Software and is ignored when TriggerCondition is None To execute a software trigger the values specified for TriggerCondition and TriggerConditionValue must be satisfied When TriggerConditionis Rising or Falling TriggerConditionValue accepts a single value When TriggerCondition is Entering or Leaving TriggerConditionValue accepts a two element vector of values Usage AI Common Access Read write Data type Double or a two element vector of doubles Read only Yes when running The default value is zero Create the analog input object ai and add one channel to it ai analoginput winsound ch addchannel ai 1 The trigger executes when a signal with a negative slope passing through 0 2 volts is detected on channel 1 set ai TriggerChannel1 ch set ai TriggerType Software set ai TriggerCondition Falling set ai TriggerConditionValue 0 2
423. ssion consists of all the steps you are likely to take when acquiring or outputting data These steps are described in the following sections Overview p 3 2 Description of the data acquisition session including a brief example Creating a Device Object Create a MATLAB object that represents the hardware subsystem p 3 4 Adding Channels or Lines Add hardware channels or hardware lines to the device object p 3 8 Configuring and Returning Define the device object behavior by assigning values to properties Properties p 3 12 Acquiring and Outputting Execute the device object and acquire or output data using the Data p 3 22 previously added channels Cleaning Up p 3 25 Remove the device object from memory and from the workspace 3 The Data Acquisition Session Overview The data acquisition session consists of all the steps you are likely to take when acquiring or outputting data These steps are 1 Create a device object You create a device object using the analoginput analogoutput or digitalio creation function Device objects are the basic toolbox elements you use to access your hardware device 2 Add channels or lines After a device object is created you must add channels or lines to it Channels are added to analog input and analog output objects while lines are added to digital I O objects Channels and lines are the basic hardware device elements with which you acquire or output data 3 Configure prop
424. st all the functions and properties associated with a specific device object A device object need not exist for you to obtain this information For example to display all the functions and properties associated with an analog input object as well as the constructor M file help daqhelp analoginput To display help for the SampleRate property daqhelp SampleRate You can also display help for an existing device object For example to display help for the BitsPerSample property for an analog input object associated with a sound card ai analoginput winsound out daghelp ai BitsPerSample Alternatively you can display help via the Workspace browser by right clicking a device object and selecting Explore gt DAQ Help from the context menu Getting Help The propinfo Function You can use the propinfo function to return the characteristics of Data Acquisition Toolbox properties For example you can find the default value for any property using this function propinfo returns a structure containing the fields shown below Table 2 2 propinfo Fields Field Name Description Type The property data type Possible values are callback any double and string Constraint The type of constraint on the property value Possible values are callback bounded enum and none ConstraintValue The property value constraint The constraint can be a range of valid values or a list of valid string values DefaultValue The p
425. stacles you need to experiment with different hardware and software configurations In other words you need to perform multiple data acquisition trials 1 2 The Data Acquisition System The Data Acquisition System As a user of MATLAB and the Data Acquisition Toolbox you are interested in measuring and analyzing physical phenomena The purpose of any data acquisition system is to provide you with the tools and resources necessary to do so You can think of a data acquisition system as a collection of software and hardware that connects you to the physical world A typical data acquisition system consists of these components e Data acquisition hardware At the heart of any data acquisition system lies the data acquisition hardware The main function of this hardware is to convert analog signals to digital signals and to convert digital signals to analog signals e Sensors and actuators transducers Sensors and actuators can both be transducers A transducer is a device that converts input energy of one form into output energy of another form For example a microphone is a sensor that converts sound energy in the form of pressure into electrical energy while a loudspeaker is an actuator that converts electrical energy into sound energy Signal conditioning hardware Sensor signals are often incompatible with data acquisition hardware To overcome this incompatibility the signal must be conditioned For example you might
426. starts running 6 27 6 Analog Output 6 28 Some timer events might not be processed if your system is significantly slowed or if the TimerPeriod value is too small For example a common application for timer events is to display data However because displaying data is a CPU intensive task some of these events might be dropped To guarantee that events are not dropped you can use the SamplesOutputFcn property Trigger Event A trigger event is generated immediately after a trigger occurs This event executes the callback function specified for TriggerFen Under most circumstances the callback function is not guaranteed to complete execution until sometime after Sending is set to On Recording and Retrieving Event Information While the analog output object is running certain information is automatically recorded in the EventLog property for some of the event types listed in the preceding section EventLog is a structure that contains two fields Type and Data The Type field contains the event type The Data field contains event specific information Events are recorded in the order in which they occur The first EventLog entry reflects the first event recorded the second EventLog entry reflects the second event recorded and so on The event types recorded in EventLog for analog output objects as well as the values for the Type and Data fields are given below Table 6 10 Analog Output Event Information Stored in EventLog
427. structure whose field names are device object properties sets the properties named in each field name with the values contained in the structure If you use the help command to display the M file help for set then you must supply the pathname shown below help daq daqdevice set Create the analog input object ai for a sound card and configure it to operate in stereo mode ai analoginput winsound addchannel ai 1 2 To display all of ai s configurable properties and their valid values set ai To set the value for the SampleRate property to 10000 set ai SampleRate 10000 The following two commands set the value for the SampleRate and InputType properties using one call to set set ai SampleRate 10000 TriggerType Manual set ai SampleRate TriggerType 10000 Manual set You can also set different channel property values for multiple channels ch ai Channel 1 2 set ch UnitsRange ChannelName 1 1 Name1 2 2 Name2 See Also Functions get setverify 10 89 setverify Purpose Syntax Arguments Description Remarks 10 90 Configure and return the specified property Actual setverify obj PropertyName PropertyValue Actual setverify obj Channel index PropertyName PropertyValue Actual setverify obj Line index PropertyName PropertyValue obj A device object or array of device objects PropertyName A property name Property
428. summary The Display Summary You can invoke the display summary by typing a DIO object or a line object at the MATLAB command line or by excluding the semicolon when e Creating a DIO object e Adding lines e Configuring property values using the dot notation You can also display summary information via the Workspace browser by right clicking a toolbox object and selecting Explore gt Display Summary from the context menu The displayed information is designed so you can quickly evaluate the status of your data acquisition session The display is divided into two main sections general summary information and line summary information General Summary Information The general display summary includes the device object type and the hardware device name followed by the port parameters The port parameters include the port ID and whether the associated lines are configurable for reading or writing Line Summary Information The line display summary includes property values associated with e The hardware line mapping e The line name e The port ID e The line direction 7 20 Evaluating the Digital O Object Status The display summary for the example given in Example Generating Timer Events on page 7 19 is shown below Display Summary of DigitalIO DIO Object Using PCI 6024E General display f f viy summary Port Parameters Port 0 is line configurable for reading and writing Engine status Engine not r
429. t Type Define a new measurement type Type MATLAB function __ Define a new measurement Cursor type None x Add Defined measurement types Type MATLAB Function CursorType M Horiz Horiz Horizontal M vert vert Vertical M Max max Horizontal M Min min Horizontal lA IMean lman Horizontal Predefined measurements M Pk2Pk peak2peak None M Freg frequency None M Period period None M RMS ims Horizontal Mv STD std Horizontal Delete OK Cancel Apply Help 9 17 9 softscope The Data Acquisition Oscilloscope 9 18 Defining a Measurement Measurements that you define for the Oscilloscope are displayed in the Measurements panel By default this panel is not included as part of the Oscilloscope To create the panel you define one or more initial measurements There are two ways to do this e Right click in the Channel Scaling panel and select Add Measurement from the menu e Use the Measurement Editor GUI which you open by selecting the Edit gt Measurement menu item Alternatively you can create an empty Measurements panel by selecting the Measurement check box in the Scope pane of the Scope Editor The Measurement pane shown below is configured to add a vertical cursor measurement for CHO to the Oscilloscope Note that the peak to peak measurement is already defined for CHO Measurement Editor xj Measurem
430. t also include the appropriate offset in the formula The A D value is constrained by the InputRange property which reflects the gain and polarity of your hardware channels and is usually returned as a voltage value You should choose an input range that utilizes the maximum dynamic range of your A D subsystem The best input range is the one that most closely encompasses the expected sensor range If the sensor signal is larger than the input range then the hardware will usually clip saturate the signal The units range is given by the UnitsRange property while the sensor range is given by the SensorRange property SensorRange is specified as a voltage value while UnitsRange is specified as an engineering unit such as Newtons or g s 1 g 9 80 m s s These property values control the scaling of data when it is extracted from the engine with the getdata function You can find the appropriate units range and sensor range from your sensor s specification sheet For example suppose SensorRange is 1 1 and UnitsRange is 10 10 If an A D value is 2 5 then the scaled value is 2 5 20 2 or 25 in the appropriate units Example Performing a Linear Conversion This example illustrates how to configure the engineering units properties for an analog input object connected to a National Instruments PCI 6024E board An accelerometer is connected to a device which is undergoing a vibration test Your job is to measure the acceler
431. t data using the daqread function The formula for converting from native data to doubles is doubles data native data native scaling native offset For analog output objects you queue native data in the engine with the putdata function The formula for converting from doubles to native data is native data doubles data native scaling native offset You return the native data type of your hardware device with the daqhwinfo function Note that the NativeScaling value for a given channel might change if you change its InputRange AI or OutputRange AO property value You might want to return or queue data in native format to conserve memory and to increase data acquisition or data output speed Usage AI AO Channel Access Read only Data type Double Read only N A when running The default value is device specific Create the analog input object ai for a National Instruments board and add eight channels to it ai analoginput nidaq 1 addchannel ai 0 7 11 53 NativeOffset See Also 11 54 Start ai collect one second of data for each channel and extract the data from the engine using the native format of the device start ai nativedata getdata ai 1000 native You can return the native data type of the board with the daqhwinfo function out daqhwinfo ai out NativeDataType ans int16 Convert the data to doubles using the NativeScaling and NativeOffset properties scaling
432. t highest value is selected If a higher value is not available then an error is returned Because the engine can set the sampling rate to a value that differs from the value you specify you should return the actual sampling rate using the get function or the device object display summary Alternatively you can use the setverify function which sets the SampleRate value and then returns the actual value that is set To find out the range of sampling rates supported by your board use the propinfo function Additionally because the actual sampling rate depends on the number of channels contained by the device object and the Channe1Skew property value AI only SampleRate should be the last property you set before starting the device object Usage AI AO Common Access Read write Data type Double Read only Yes when running The default value is obtained from the hardware driver SampleRate Example See Also Create the analog input object ai for a sound card and add two channels to it ai analoginput winsound addchannel ai 1 2 You can find out the range of valid sampling rates with the ConstraintValue field of the propinfo function rates propinfo ai SampleRate rates ConstraintValue ans 8000 48000 To configure the per channel sampling rate to 48 kHz set ai SampleRate 48000 Alternatively you can use the setverify function to configure and return the SampleRate value ActualRate setve
433. t of device objects channels and lines H BitsPerSample IE Property to configure and its current value Buffering onfig 512 30 Bufferingllode Auto Channel 2x1 aichannel Casale 0 List of configurable properties ChammelSkewllode None ClockSource Internal and their current values DatallissedAction dagqaction EventLog Type Default Value 16 Constraint Constraint Value 816 ReadOnly OFase ReadOnywhen Tu Property characteristics Device Specific T True Running BITSPERSANPLE 16 BitsPerSample specifies the number of bits the sound card uses to each zanple Property help The value of BitsPerSample cannot ke modified while the object is 3 21 3 The Data Acquisition Session 3 22 Acquiring and Outputting Data After you configure the device object you can acquire or output data Acquiring and outputting data involves these three steps 1 Starting the device object 2 Logging data or sending data 3 Stopping the device object As data is being transferred between MATLAB and your hardware you can think of the device object as being in a particular state Two types of states are defined for the Data Acquisition Toolbox e Running For analog input objects running means that data is being acquired from an analog input subsystem However the acquired data is not necessarily saved to memory or a disk file For analog output objects running me
434. t value is an empty vector Create the analog input object ai and add two channels to it ai analoginput nidaq 1 addchannel ai 0 1 Suppose you want to access filter coefficients during the acquisition You can create a structure to store these coefficients which can then be stored in UserData coeff a 1 0 coeff b 1 25 set ai UserData coeff 11 101 UserData 11 102 Device Specific Property Reference This chapter describes all toolbox device specific properties Device specific properties apply only to hardware devices of a specific type or from a specific vendor For example the BitsPerSample property is supported only for sound cards while the NumMuxBoards property is supported only for National Instruments devices The sections are as follows Getting Command Line How to use the daghelp and propinfo functions to return property help Property Help p 12 2 Properties By Vendor Contains a series of tables that group properties by vendor p 12 3 Properties Alphabetical Lists all the base properties alphabetically List p 12 7 12 Device Specific Property Reference Getting Command Line Property Help To get command line property help you should use the daghelp function For example to get help for the sound card s BitsPerSample property daqhelp BitsPerSample Note You can use daghelp without creating a device object You can also get property characteristics s
435. ta is a CPU intensive task some of these events might be dropped To guarantee that events are not dropped use the SamplesAcquiredFcn property Trigger Event A trigger event is generated immediately after a trigger occurs This event executes the callback function specified for the TriggerFen property Under most circumstances the callback function is not guaranteed to complete execution until sometime after Logging is set to On 5 47 5 Doing More with Analog Input 5 48 Recording and Retrieving Event Information While the analog input object is running certain information is automatically recorded in the EventLog property for some of the event types listed in the preceding section EventLog is a structure that contains two fields Type and Data The Type field contains the event type The Data field contains event specific information Events are recorded in the order in which they occur The first EventLog entry reflects the first event recorded the second EventLog entry reflects the second event recorded and so on The event types recorded in EventLog for analog input objects as well as the values for the Type and Data fields are given below Table 5 12 Analog Input Event Information Stored in EventLog Event Type Type Field Value Data Field Value Data missed DataMissed RelSample Input overrange OverRange RelSample Channel OverRange Run time error Error AbsTime RelSample String Start Start AbsTime RelSample
436. ta to be queued in the engine putsample obj data immediately outputs the row vector data which consists of one sample for each channel contained by obj Using putsample is a good way to test your analog output configuration Additionally e putsample does not store samples in the data acquisition engine putsample can be executed at any time after channels have been added to obj putsample is not supported for sound cards Create the analog output object ao for a National Instruments board and add two hardware channels to it ao analogoutput nidaq 1 ch addchannel ao 0 1 To call putsample for ao putsample ao 1 1 Functions putdata putvalue Purpose Syntax Arguments Description Remarks Example Write values to lines putvalue obj data putvalue obj Line index data obj A digital I O object obj Line index One or more lines contained by obj data A decimal value or binary vector putvalue obj data writes data to the hardware lines contained by the digital I O object obj putvalue obj Line index data writes data to the hardware lines specified by obj Line index More About Writing Values to Lines e You can specify data as either a decimal value or a binary vector A binary vector or binvec is constructed with the least significant bit LSB in the first column and the most significant bit MSB in the last column For example the decimal number 23 is written
437. tal values just as you would with a typical DIO subsystem To access the physical parallel port lines most PCs come equipped with one 25 pin female connector which is shown below 1 oOo0oo0oo0oo0oo0o0000000 25 pin female parallel port oOocoo0oo00000000 connector with pin assignments 25 The lines use TTL logic levels A line is high true or asserted when it is a TTL high level while a line is low false or unasserted when it is a TTL low level The exceptions are lines 1 11 14 and 17 which are hardware inverted 7 7 7 Digital Input Output The toolbox groups the 17 nonground lines into three separate ports The port IDs and the associated pin numbers are given below Table 7 3 Parallel Port IDs and Pin Numbers Port ID Pins Description 0 2 9 Eight I O lines with pin 9 being the most significant bit MSB 1 10 138 Five input lines used for status and 15 2 1 14 16 Four T O lines used for control and 17 Note that in some cases port 0 lines might be unidirectional and only output data If supported by the hardware you can configure these lines for both input and output with your PC s BIOS by selecting a bidirectional mode such as EPP Enhanced Parallel Port or ECP Extended Capabilities Port The parallel port characteristics for the DIO object parport are shown below hwinfo daghwinfo parport hwinfo Port 1 ans ID 0 LineIDs 0 123 45 6 7 Direction in out Config po
438. te memory automatically or manually If Buf feringMode is Auto the BufferingConfig values are automatically set by the engine If BufferingMode is Manual then you must manually set the BufferingConfig values If you change the Buf feringConfig values BufferingMode is automatically set to Manual When memory is automatically allocated by the engine the block size value depends on the sampling rate and is typically a binary number The number of blocks is initially set to a value of 30 but can dynamically increase to accommodate the memory requirements In most cases the number of blocks used results in a per channel memory that is somewhat greater than the SamplesPerTrigger value When you manually allocate memory the number of blocks is not dynamic and care must be taken to ensure there is sufficient memory to store the acquired data If the number of samples acquired or queued exceeds the allocated memory then an error is returned You can easily determine the memory allocated and available memory for each device object with the daqmem function Usage AI AO Common Access Read write Data type Two element vector of doubles Read only Yes when running 11 15 BufferingConfig Values Example See Also 11 16 The default value is determined by the engine and is based on the number of channels contained by the device object and the sampling rate The BufferingMode value determines whether the values are automatically upd
439. ted to the CALOUT line in the module If SourceOutput is Open the source remains open circuited even when the source is started The impedance on the output is only about 1 kilohm because the power fail decay circuit is still connected to the output If SourceOutput is CALOUT the source output is connected to the module s internal CALOUT line This allows the module s CALOUT line to be driven by an external signal applied at the source output connector If SourceOutput is SRC amp CALOUT the source output is connected to the module s internal CALOUT line and the source D A converter is also connected to the CALOUT line This is a combination of the Grounded and CALOUT values and is useful for multimainframe calibration Vendor Agilent Technologies Usage AO Channel Access Read write Data Type String Read only Yes when running SourceOutput Values Normal Grounded Open CALOUT SRC amp CALOUT Normal source output The source output connector remains grounded while the source D A converter is internally connected to the CALOUT line in the module The source remains open circuited even when the source is started The source output is connected to the module s internal CALOUT line The source output connector remains grounded while the source D A converter is internally connected to the CALOUT line in the module The source output is also connected to the module s internal CALOUT line 12 2
440. th the set command Data type the property data type The supported data types include action function double string Channel Line and any Read only when running whether a property value can be configured while the device object is running Valid property values including the default value When property values are given by an enumerated list the default value is usually indicated by Default values for some properties are calculated by the data acquisition engine while others are determined by the hardware driver If there are device specific enumerated values they are listed separately e An example using the property e Related properties and functions 12 7 BiDirectionalBit Purpose Description Characteristics Values 12 8 Specify the BIOS control register bit that determines bidirectional operation BiDirectionalBit can be 5 6 or 7 The default value is 5 because most parallel port hardware uses bit 5 of the BIOS control register to determine the direction input or output of port 0 If port 0 is unable to input data you need to configure the BiDirectionalBit value to 6 or 7 Typically you will not know the bit value required by your port and some experimentation is required Vendor Usage Access Data type Read only when running 5 6 or 7 Parallel port DIO Common Read write Double Yes The BIOS control register bit that determines bidirectional operation Bit
441. th the whos command whos hwlines Name Size Bytes Class hwlines 8x1 536 dioline object Grand total is 13 elements using 536 bytes You can use hwlines to easily access lines For example you can configure or return property values for one or more lines As described in Referencing Individual Hardware Lines on page 7 9 you can also access lines with the Line property 7 4 Adding Lines to a Digital I O Object Once you add lines to a DIO object the properties listed below are automatically assigned values These properties provide descriptive information about the lines based on their class type and ID Table 7 2 Descriptive Digital I O Line Properties Property Name Description HwLine Index Parent Type Specify the hardware line ID Indicate the MATLAB index of a hardware line Indicate the parent device object of a line Indicate a line You can display the values of these properties for chans with the get function get hwlines HwLine Index Parent Type ans 0 1 2 3 4 5 6 7 Line and Port Characteristics 1 2 3 4 5 6 7 8 1x1 1x1 1x1 1x1 1x1 1x1 1x1 1x1 digitalio digitalio digitalio digitalio digitalio digitalio digitalio digitalio Line Line Line Line Line Line Line Line As described in the preceding section when you add lines to a DIO object they must be configu
442. that you can change the indicator locations graphically by placing the mouse cursor over the indicator and sliding it to the desired location 9 15 9 softscope The Data Acquisition Oscilloscope 9 16 Configuring Trigger Properties You can change the characteristics of the labels associated with the Triggers panel with the Scope Editor GUI To open this GUI select Scope from the Edit menu choose the Scope Properties pane and select Triggers from the Select the scope components list box The Scope Properties pane is shown below Scope Editor x Scope Scope Properties Select the scope components display a display2 Select Triggers Channel Scaling X Editthe selected scope components properties Name Triggers ShowName PE True Click Help to view property descriptions OK Cancel Help Making Measurements Making Measurements You can make measurements on the acquired data with the Measurements panel The Oscilloscope provides many predefined measurement types such as horizontal and vertical cursors and basic math calculations such as the mean and standard deviation Additionally you can define new measurement types that suit your specific needs As shown below you can list the predefined measurement types and create a new measurement type with the Measurement Type pane of the Measurement Editor GUI Measurement Editor x Measurement Measurement Properties Measuremen
443. the Expression field Defining a math channel is similar to defining a reference channel The main difference is in specifying the expression For a reference channel you specify a MATLAB variable or expression For a math channel you specify e The channel name Channel names are given by the Name column in the Defined channels table e A valid MATLAB expression When the expression is evaluated the channel names are replaced with the associated data that is currently being displayed Displaying Channels The Channel pane shown below is configured to create a math channel called m1 using the CHO and CH1 data and to display the math channel data with CH1 in display1 Channel Editor j xi Channel Channel Properties Channel Display Define a new channel Type math x 7 OO T Define a math channel named m1 a using the data from CHO and CH1 Expression Jabs CHO abs CH1 Display faisai Display the math channel data with CH1 a S lick the Add button to include Defined channels the new channel in the table Type Name Data Source Display M Hardware CH0 Hardware channel 0 display2 M Hardware CH1 Hardware channel 1 displayi M Reference r1 y2 Click the OK or Apply button to create Ex _cancet_ aw Hep the math channel The traces for the hardware math and reference channels are shown below Oscilloscope loj x File Edit Help Channel Scaling Trig
444. the same format as returned by get For example if get returns the ChannelName property value as Left you must specify Left as the property value in daqf ind case matters However case does not matter when you specify enumerated property values For example daqfind will find a device object with a Running property value of On or on You can use daqfind to return a cleared device object ai analoginput winsound ch addchannel ai 1 2 set ch ChannelName Joe Jack clear ai ainew daqfind To return the channel associated with the descriptive name Jack ch2 daqfind ainew ChannelName Jack To return the device object with a sampling rate of 8000 Hz and the descriptive name winsoundO AI you can pass a structure to daqfind S Name winsound0 AI S SampleRate 8000 daqobj daqfind S Functions clear get propinfo daghelp Purpose Syntax Arguments Description Display help for device objects constructors adaptors functions and properties daqhelp out daghelp name out daghelp obj out daghelp obj name name A device object constructor adaptor function or property name obj A device object out Contains the specified help text daghelp displays a complete listing of Data Acquisition Toolbox constructors and functions along with a brief description of each out daghelp name returns help for the device object constructor adaptor fun
445. the variables bsize P and T are passed to the callback function duration 10 Ten second duration set AI SampleRate 22050 ActualRate get AI SampleRate set AI SamplesPerTrigger duration ActualRate set AI TimerPeriod 0 5 bsize AI SampleRate AI TimerPeriod figure P plot zeros bsize 1 T title Number of callback function calls num2str 0 xlabel Samples ylabel Signal Volts grid on set gcf doublebuffer on set AI TimerFcn daqdoc5 7plot bsize P T 4 Acquire data Start AI The drawnow command in daqdoc5 7plot forces MATLAB to update the display The waittilstop function blocks the MATLAB command line and waits for AI to stop running start AI waittilstop AI duration Clean up When you no longer need AI you should remove it from memory and from the MATLAB workspace delete AI clear AI linearly Scaling the Data Engineering Units Linearly Scaling the Data Engineering Units The Data Acquisition Toolbox provides you with a way to linearly scale analog input signals from your sensor You can associate this scaling with specific engineering units such as volts or Newtons that you might want to apply to your data When specifying engineering units there are three important considerations e The expected data range produced by your sensor This range depends on the physical phenomena you are measuring and the maximum output range of the s
446. the vendor or the operating system sound cards and do not involve using the Data Acquisition Toolbox The sections are as follows Agilent Technologies How to use the Soft Front Panel Hardware p A 2 Measurement Computing How to use InstaCal Hardware p A 5 National Instruments How to use the Measurement amp Automation Explorer Hardware p A 8 Sound Cards p A 11 How to use Windows resources Other Things to Try How to register the hardware driver adaptor or contact The MathWorks p A 18 To accurately test your hardware you should use these vendor tools to match the requirements of your data acquisition session For example you should select the appropriate sampling rate number of channels acquisition mode continuous or single point and input range If these tests do not help you then you might need to register the hardware driver adaptor or contact The MathWorks for support Contact information is provided in Contacting The MathWorks on page A 19 as well as in the beginning of this guide If the problem is with your hardware then you should contact the hardware vendor Note that if you cannot access your board using the vendor s software then you will not be able to do so with the Data Acquisition Toolbox A Troubleshooting Your Hardware Agilent Technologies Hardware If you are having trouble using the Data Acquisition Toolbox with a supported Agilent Technologies device the reason might be that
447. then you need to register it manually using the daqregister function For example to manually register the sound card adaptor daqregister winsound A 18 Other Things to Try If you are using a third party adaptor then you might need to register it manually If so you must supply the full pathname to daqregister For example to register the third party adaptor myadaptor d11 daqregister D MATLABR12 toolbox daq myadaptors myadaptor d11 Note You must install the associated hardware driver before adaptor registration can occur Contacting The MathWorks If you need support from The MathWorks visit our Web site at http www mathworks com support or e mail us at support mathworks com Before contacting The MathWorks you should run the daqsupport function This function returns diagnostic information such as e The versions of the MathWorks products you are using e Your MATLAB path e The characteristics of your hardware The output from daqsupport is automatically saved to a text file which you can use to help troubleshoot your problem For example if you are having trouble with your sound card type daqsupport winsound A Troubleshooting Your Hardware A 20 Managing Your Memory Resources This appendix describes how to manage memory resources The sections are as follows Memory Allocation p B 2 How the toolbox automatically allocates memory resources and how you can overrid
448. tion engine The output out is an array out daqfind PropertyName PropertyValue returns all device objects channels or lines that exist in the data acquisition engine and have the specified property names and property values The property name property value pairs can be specified as a cell array out daqfind S returns all device objects channels or lines that exist in the data acquisition and have the property names and property values specified by S S is a structure with field names that are property names and field values that are property values out daqfind obj PropertyName PropertyValue returns all device object channels or lines listed by obj that have the specified property names and property values 10 27 daafind Remarks Example See Also 10 28 More About Finding Device Objects Channels or Lines daqfind is particularly useful in these circumstances e A device object is cleared from the MATLAB workspace and it needs to be retrieved from the data acquisition engine e You need to locate device objects channels or lines that have particular property names and property values Rules for Specifying Property Names and Property Values e You can use property name property value string pairs structures and cell array pairs in the same call to daqf ind However in a single call to daqf ind you can specify only device object properties or channel line properties e You must use
449. tion starts immediately after you press the Trigger button and is independent of the data Note that the Sequence acquisition does not support this trigger type Triggering the Oscilloscope The Oscilloscope shown below is configured for a one shot acquisition of 1000 samples for CHO and CH1 The acquisition is dependent on the data and is initiated when a rising signal level of 3 3 volts is detected on CHO Additionally the first 0 02 second of data is defined as pretrigger data Oscilloscope oj xj Channel Scaling Triggers Horizontal Acquire One Shot x File Edit Help Offset Scale Samples to acquire a C Fillthe display Count hooo Vertical ico Type dependent x CH1 Channel jen z Condition Rising x Value fa 000 valuez p J D TE Pretrigger 10 02 sec CHO 2 67 30Vidiv 5 0037msidiv On Trigger Trigger level Pretrigger data Configure a one shot indicator indicator dependent trigger offset Scale When you use a dependent trigger type the display associated with the selected channel contains these two indicators e The trigger level on the vertical axis e The location of the start of the trigger on the horizontal axis The start of the trigger corresponds to the first acquired sample at time zero As shown by the data tips for CH1 data to the left of the indicator is defined as pretrigger data and has negative time values Note
450. tive channel names MATLAB Indices Every hardware channel contained by an analog input object has an associated MATLAB index that is used to reference the channel When adding channels with the addchannel function index assignments can be made automatically or manually In either case the channel indices start at 1 and increase monotonically up to the number of channel group members For example the analog input object ai created in the preceding section had the MATLAB indices 1 and 2 automatically assigned to the hardware channels 0 and 1 respectively To manually swap the hardware channel order you supply the appropriate index to chans and use the HwChannel property chans 1 HwChannel 1 chans 2 HwChannel 0 Alternatively you can use the Channel property ai Channel 1 HwChannel 1 ai Channel 2 HwChannel 0 Note that you can also use addchannel to specify the required channel order chans addchannel ai 1 0 Descriptive Channel Names Choosing a unique descriptive name can be a useful way to identify and reference channels particularly for large channel groups You can associate descriptive names with hardware channels using the addchannel function For example suppose you want to add 16 single ended channels to ai and you want to associate the name TrigChan with the first channel in the group ai InputType SingleEnded addchannel ai 0O TrigChan addchannel ai 1 15 4 5 4 Getting Started
451. tively you can specify the callback function as a cell array ai SamplesAcquiredFcn mycallback M file callback functions require at least two input arguments The first argument is the device object The second argument is a variable that captures the event information given in Table 5 12 Analog Input Event Information Stored in EventLog on page 5 48 This event information pertains only to the event that caused the callback function to execute The function header for mycallback is shown below function mycallback obj event You pass additional parameters to the callback function by including both the callback function and the parameters as elements of a cell array For example to pass the MATLAB variable time to mycallback time datestr now 0 ai SamplesAcquiredFcnCount 1000 ai SamplesAcquiredFcn mycallback time 5 51 5 Doing More with Analog Input 5 52 Alternatively you can specify mycallback as a string in the cell array ai SamplesAcquiredFcn mycallback time The corresponding function header is function mycallback obj event time If you pass additional parameters to the callback function then they must be included in the function header after the two required arguments Note You can also specify the callback function as a string In this case the callback is evaluated in the MATLAB workspace and no requirements are made on the input arguments of the callback function Specif
452. tively you can use the setverify function ActualRange setverify ai Channel InputRange 10 10 Functions daqhwinfo setverify Properties InputOverRangeFcn SensorRange Units UnitsRange InputType Purpose Description Characteristics Values Specify the analog input hardware channel configuration For National Instruments devices InputType can be SingleEnded Differential or NonReferencedSingleEnded For Measurement Computing devices InputType can be SingleEnded or Differential for Agilent Technologies devices InputType can only be Differential For sound cards InputType can only be AC Coupled If channels have been added to a National Instruments or Measurement Computing analog input object and you change the InputType value then the channels are automatically deleted if the hardware reduces the number of available channels Usage AI Common Access Read write Data type String Read only Yes when running Agilent Technologies Differential Channels are configured for differential input Keithley and Measurement Computing Differential Channels are configured for differential input SingleEnded Channels are configured for single ended input 11 41 InputType National Instruments Differential Channels are configured for differential input SingleEnded Channels are configured for single ended input NonReferenced This channel configuration is used when the input SingleEnded sign
453. to get get ai SampleRate ans 8000 To display the current values for multiple properties you include the property names as elements of a cell array Configuring and Returning Properties get ai StandardSampleRates Running ans On OFT You can also use the dot notation to display a single property value ai TriggerType ans Immediate Channel and Line Properties To return all configurable channel line property names and their possible values for a single channel line contained by a device object you must use the Channel Line property For example to display the configurable channel properties for the first channel contained by ai set ai Channel 1 ChannelName HwChannel InputRange SensorRange Units UnitsRange All channel properties and their current values for the first channel contained by ai are shown below get ai Channel 1 ChannelName Left HwChannel 1 Index 1 InputRange 1 1 NativeOffset 1 5259e 005 NativeScaling 3 0518e 005 Parent 1x1 analoginput SensorRange 1 1 Type Channel Units Volts UnitsRange 1 1 As described in the preceding section you can also return values for a specified number of channel properties with the get function or the dot notation 3 The Data Acquisition Session 3 18 Configuring Property Values You configure property values with the set function or the dot notation In practice you can configure
454. to Internal which specifies that the acquisition rate is governed by the internal hardware clock For subsystems without a hardware clock you must use software clocking to govern the sampling rate Software clocking allows a maximum sampling rate of 500 Hz and a minimum sampling rate of 0 0002 Hz An error is returned if more than 1 sample of jitter is detected Note that you might not be able to attain rates over 100 Hz on all systems especially Windows 9X Usage Access Data type Read only when running AI AO Common Read write String Yes Agilent Technologies Internal External Inverted External VXIBus 3 VXIBusSample The internal hardware clock is used The external sample clock positive true The external sample clock negative true The VXI bus clock divided by 3 provided by some other clock master The VXI bus sample clock ClockSource See Also Keithley Internal External Software The internal hardware clock is used Externally control the channel clock Note that the ChannelSkew property value is honored The computer clock is used Measurement Computing Internal External Software The internal hardware clock is used AI only Externally control the channel clock AI only The computer clock is used National Instruments Internal External ExternalSample Ctrl ExternalScan Ctrl ExternalSample AndScanCtrl The internal hardware clock is used
455. to the channels addchannel AI1 0 3 chan1 chan2 chan3 chan4 Note that you can use the makenames function to create a cell array of channel names If you add channels 4 5 and 7 to the existing channel group addchannel AI1 4 5 7 the new channels are automatically assigned the indices 5 7 Suppose instead you add channels 4 5 and 7 to the channel group and explicitly assign them indices 1 3 addchannel AI1 4 5 7 1 3 The new channels are assigned the indices 1 3 and the previously defined channels are reindexed as indices 4 7 However if you assigned channels 4 5 and 7 to indices 6 8 an error is returned because there is a gap in the indices index 5 has no associated hardware channel 10 11 addchannel See Also 10 12 Sound Card Suppose you create the analog input object AI1 for a sound card Most sound cards have only two channels that can be added to a device object To configure the sound card to operate in mono mode you must specify hwch as 1 AI1 analoginput winsound addchannel AI1 1 The ChannelName property is automatically assigned the value Mono You can now configure the sound card to operate in stereo mode by adding the second channel addchannel AI1 2 The ChannelName property is assigned the values Left and Right for the two hardware channels Alternatively you can configure the sound card to operate in stereo mode with one call to addchannel addchannel AI1 1
456. tops running e If samples is greater than the number of samples currently acquired all available samples are returned with a warning message stating that the requested number of samples were not available peekdata Example See Also Create the analog input object ai for a National Instruments board add eight input channels and configure ai for a two second acquisition ai analoginput nidaq 1 addchannel ai 0 7 set ai SampleRate 2000 set ai SamplesPerTrigger 4000 After issuing the start function you can preview the data start ai data peekdata ai 100 peekdata returns 100 samples to data for all eight channel group members If 100 samples are not available then whatever samples are available will be returned and a warning message is issued The data is not removed from the data acquisition engine Functions getdata getsample Properties SamplesAvailable 10 79 propinfo Purpose Syntax Arguments Description 10 80 Return property characteristics for device objects channels or lines out propinfo obj out propinfo obj obj PropertyName out out propinfo obj PropertyName A device object channels or lines A valid obj property name A structure whose field names are the property names for obj if PropertyName is not specified returns the structure out whose field names are the property names for obj Each property name in out contains
457. ts range sensor range The A D value is constrained by the InputRange property which reflects the gain and polarity of your analog input channels The sensor range is given by the SensorRange property which reflects the range of data you expect from your sensor For analog output objects the data is scaled when it is queued in the engine with the putdata function according to the formula scaled value original value output range units range The output range is constrained by the OutputRange property which specifies the gain and polarity of your analog output channels For both objects you can also use the Units property to associate a meaningful label with your data Usage AI AO Channel Access Read write Data type Two element vector of doubles Read only No when running The default value is determined by the default value of the InputRange or the OutputRange property Functions getdata putdata Properties InputRange OutputRange SensorRange Units UserData Purpose Description Characteristics Values Example Store data that you want to associate with a device object UserData stores data that you want to associate with the device object Note that if you return analog input object information to the MATLAB workspace using the daqread function the UserData value is not restored Usage AI AO DIO Common Access Read write Data type Any type Read only No when running The defaul
458. ty 11 72 SamplesPerTrigger property 11 73 sampling 1 15 sampling rate AI subsystem 5 5 AO subsystem 6 5 saturation 6 35 save function 10 86 saving device objects MAT file 8 4 M file 8 2 information to disk AI 8 5 Oscilloscope configuration 9 25 property values to a MAT file 8 2 scaling the data AI object 5 55 AO object 6 34 scanning hardware 1 16 channel order 4 4 Scope Editor GUI Scope pane 9 5 Scope Properties pane 9 12 sending data 3 22 Sending property 11 74 SensorRange property 11 75 sensors 1 7 range 11 75 session 3 1 3 2 loading 8 2 saving 8 2 set function 10 87 settling time 1 30 setverify function 10 90 showdaqevents function 10 92 signal conditioning 1 10 simultaneous input and output 6 37 simultaneous sample and hold hardware 1 18 single ended inputs 1 24 single point acquisition 10 63 output 10 84 size function 10 94 skew 5 6 softscope function 10 96 software clock 1 22 MCC hardware 11 24 software trigger 5 22 sound cards channel configuration 5 4 device specific properties 12 6 mono mode 4 6 standard sample rates 12 26 stereo mode 4 7 troubleshooting A 11 SourceMode property 12 21 SourceOutput property 12 22 Span property 12 24 StandardSampleRates property 12 26 start event AI object 5 47 AO object 6 27 start function 10 104 StartFen AI object 5 47 AO object 6 27 StartFen property 11 76 starting multiple device objects 6 37 Index state logging 3 22 running 3 22 s
459. uch as the default property value using the propinfo function For example suppose you create the analog input object ai for a sound card and want to find the default value for the BitsPerSample property ai analoginput winsound out propinfo ai BitsPerSample out DefaultValue ans 16 12 2 Properties By Vendor Properties By Vendor This section contains brief descriptions of all toolbox device specific properties The properties are grouped according to these supported vendors e Agilent Technologies properties e Keithley properties e Measurement Computing properties e National Instruments properties e Parallel port properties e Sound card properties multi vendor You can display device specific properties with the set function The device specific properties are displayed after the base properties Note Some device specific property values are not available for all devices Refer to your hardware documentation for detailed information about device specific behavior Agilent Technologies Properties The device specific Agilent Technologies properties for analog input AI and analog output AO objects are given below Property Name Description Device Objects COLA Specify whether the source constant level AO output is enabled or disabled Coupling Specify the input coupling mode Al GroundingMode Specify the input channel grounding mode Al InputMode Specify the channel in
460. ude If the signal is smaller than a few millivolts you might need to amplify it If it is larger than the maximum range of your analog input hardware typically 10 V you will have to divide the signal down using a resistor network The amplitude is related to the sensitivity resolution of your hardware Refer to Accuracy and Precision on page 1 28 for more information about hardware sensitivity The Data Acquisition System e Frequency Whenever you acquire data you should decide the highest frequency you want to measure The highest frequency component of the signal determines how often you should sample the input If you have more than one input but only one analog input subsystem then the overall sampling rate goes up in proportion to the number of inputs Higher frequencies might be present as noise which you can remove by filtering the signal before it is digitized If you sample the input signal at least twice as fast as the highest frequency component then that signal will be uniquely characterized However this rate might not mimic the waveform very closely For a rapidly varying signal you might need a sampling rate of roughly 10 to 20 times the highest frequency to get an accurate picture of the waveform For slowly varying signals you need only consider the minimum time for a significant change in the signal The frequency is related to the bandwidth of your measurement Bandwidth is discussed in the next
461. uency divided by 2 56 Valid spans are given by the maximum span divided by powers of two and the maximum span divided by five and by powers of two The value set for Span automatically updates the SampleRate value See Also Properties SampleRate 12 25 StandardSampleRates Purpose Description Characteristics Values 12 26 Specify whether the valid sample rates snap to a small set of standard values or if you can set the sample rate to any value within the allowed bounds StandardSampleRates can be On of Off If StandardSampleRates is Off then it is possible to set the sample rate to any value within the bounds supported by the hardware For most sound cards the lower bound is 8 000 kHz while the upper bound is 44 1 kHz For newer sound cards an upper bound of 96 0 kHz might be supported The specified sample rate is rounded up to the next integer value If StandardSampleRates is On then the available sample rates snap to a small set of standard values The standard values are 8 000 kHz 11 025 kHz 22 050 kHz and 44 100 kHz If you specify a sampling rate that is within one percent of a standard value then the sampling rate snaps to that standard value If you specify a sampling rate that is not within one percent of a standard value then the sampling rate rounds up to the closest standard value Regardless of the StandardSampleRates value if you specify a sampling rate that is outside the allowed limits then an
462. uisition hardware At a minimum this involves connecting a sensor to a plug in or external data acquisition device 2 Configure your data acquisition session This involves creating a device object adding channels setting property values and using specific functions to acquire data 3 Analyze the acquired data using MATLAB Simple data acquisition applications using a sound card and a National Instruments board are given below Acquiring Data with a Sound Card Suppose you must verify that the fundamental lowest frequency of a tuning fork is 440 Hz To perform this task you will use a microphone and a sound card to collect sound level data You will then perform a fast Fourier transform FFT on the acquired data to find the frequency components of the tuning fork The setup for this task is shown below Data Source Sensor Sound Card Data Sink Figure VW AD MATLAB workspace Analog Input Examples Configuring the Data Acquisition Session For this example you will acquire 1 second of sound level data on one sound card channel Because the tuning fork vibrates at a nominal frequency of 440 Hz you can configure the sound card to its lowest sampling rate of 8000 Hz Even at this lowest rate you should not experience any aliasing effects because the tuning fork will not have significant spectral content abo
463. uments Description Remarks Create a digital I O object DIO digitalio adaptor 1D adaptor The hardware driver adaptor name The supported adaptors are keithley mcc nidaq and parallel ID The hardware device identifier DIO The digital I O object DIO digitalio adaptor ID creates the digital I O object DIO for the specified adaptor and for the hardware device with device identifier ID ID can be specified as an integer or a string More About Creating Digital I O Objects e When a digital I O object is created it does not contain any hardware lines To execute the device object hardware lines must be added with the addline function e You can create multiple digital I O objects that are associated with a particular digital I O subsystem However you can typically execute only one object at a time e The digital I O object exists in the data acquisition engine and in the MATLAB workspace If you create a copy of the device object it references the original device object in the engine e The Name property is automatically assigned a descriptive name that is produced by concatenating adaptor ID and DIO You can change this name at any time The Parallel Port Adaptor The toolbox provides basic DIO capabilities through the parallel port The PC supports up to three parallel ports that are assigned the labels LPT1 LPT2 and LPTS3 You can use only these ports If you add additional ports to your system
464. ur data acquisition hardware There are two main types of sensors based on the output they produce digital sensors and analog sensors Digital sensors produce an output signal that is a digital representation of the input signal and has discrete values of magnitude measured at discrete times A digital sensor must output logic levels that are compatible with the digital receiver Some standard logic levels include transistor transistor logic TTL and emitter coupled logic ECL Examples of digital sensors include switches and position encoders Analog sensors produce an output signal that is directly proportional to the input signal and is continuous in both magnitude and in time Most physical variables such as temperature pressure and acceleration are continuous in nature and are readily measured with an analog sensor For example the temperature of an automobile cooling system and the acceleration produced by a child on a swing all vary continuously The sensor you use depends on the phenomena you are measuring Some common analog sensors and the physical variables they measure are listed below Table 1 1 Common Analog Sensors Sensor Physical Variable Accelerometer Acceleration Microphone Pressure Pressure gauge Pressure Resistance temperature Temperature device RTD Strain gauge Force Thermocouple Temperature 1 7 T introduction to Data Acquisition 1 8 When choosing the best analog sensor to use you
465. use multiple channels those channels cannot be sampled simultaneously and a time gap exists between consecutive sampled channels This time gap is called the channel skew You can think of the channel skew as the time it takes the analog input subsystem to sample a single channel The Analog Input Subsystem Additionally the maximum sampling rate your hardware is rated at typically applies for one channel Therefore the maximum sampling rate per channel is given by the formula Maximum sampling rate per channel ___ Maximum board rate _ Number of channels scanned Typically you can achieve this maximum rate only under ideal conditions In practice the sampling rate depends on several characteristics of the analog input subsystem including the settling time and the gain as well as the channel skew The sample period and channel skew for a multichannel configuration using scanning hardware is shown below A Group Group Group scan 1 scan 2 scan n p E O E Sn o o o ep a o o o E a Q 9 5 o o o o o j Sample period Channel skew gt Time If you cannot tolerate channel skew in your application you must use hardware that allows simultaneous sampling of all channels Simultaneous sample and hold hardware is discussed in the next section T introduction to Data Acquisition Simultaneous Sample and Hold Hardware Simultaneous sample and hold SS H hardware samples all input signals at the
466. using an analog input object You can run this example by typing daqdoc3_1 at the MATLAB command line 1 Create a device object Create the analog input object AI for a sound card The installed adaptors and hardware IDs are found with daqhwinfo AI analoginput winsound AI analoginput nidaq 1 AI analoginput mcc 1 oe oe 2 Add channels Add two channels to AI addchannel AI 1 2 addchannel AI 0 1 For NI and MCC 3 Configure property values Configure the sampling rate to 11 025 kHz and define a 2 second acquisition set AI SampleRate 11025 set AI SamplesPerTrigger 22050 4 Acquire data Start AI and extract all the data from the engine Before start is issued you might want to begin inputting data from a microphone or a CD player start AI data getdata AI Plot the data and label the figure axes plot data xlabel Samples ylabel Signal Volts 5 Clean up When you no longer need AI you should remove it from memory and from the MATLAB workspace delete AI clear AI 3 3 3 The Data Acquisition Session 3 4 Creating a Device Object Device objects are the toolbox components you use to access your hardware device They provide a gateway to the functionality of your hardware and allow you to control the behavior of your data acquisition application Each device object is associated with a specific hardware subsystem To create a device object y
467. ut object involves specifying the trigger type Trigger types are specified with the TriggerType property The valid TriggerType values that are supported for all hardware are given below Table 6 4 Analog Output TriggerType Property Values TriggerType Values Description Immediate The trigger occurs just after you issue the start function Manual The trigger occurs just after you manually issue the trigger function Most devices have hardware specific trigger types which are available to you through the TriggerType property For example to see all the trigger types including hardware specific trigger types for the analog output object ao created in the preceding section set ao TriggerType Manual Immediate HwDigital This information tells you that the National Instruments board also supports a hardware digital trigger For a description of device specific trigger types refer to Device Specific Hardware Triggers on page 6 24 or the TriggerType reference pages in Chapter 11 Base Property Reference 6 7 6 Analog Output 6 8 Outputting Data After you configure the analog output object you can output data Outputting data involves these three steps 1 Queuing data 2 Starting the analog output object 3 Stopping the analog output object Queuing Data in the Engine Before you can start the device object data must be queued in the engine Data is queued in the engine with the
468. value DefaultValue Hold the value specified by DefaultChannelValue Create the analog output object ao and add two channels to it ao analogoutput nidaq 1 addchannel ao 0 1 You can configure ao so that when queued data is finished being output a value of 1 volt is held for both channels ao OutOfDataMode DefaultValue ao Channel DefaultChannelValue 1 0 Properties DefaultChannelValue PortAddress Purpose Description Characteristics Values Example Indicate the base address of the parallel port The PC supports up to three parallel ports that are assigned the labels LPT1 LPT2 and LPTS You can use any of these standard ports as long as they use the usual base addresses which are in hex 378 278 and 3BC respectively Additional ports or standard ports not assigned the usual base addresses are not accessible by the toolbox Note that most PCs that support MATLAB will include a single parallel printer port with base address 378 LPT1 Vendor Parallel port Usage DIO Common Access Read only Data Type String Read only Yes when running The value is automatically defined when the object is created Create a digital I O object for parallel port LPT1 and return the PortAddress value dio digitalio parallel LPT1 get dio PortAddress ans 0x378 The returned value indicates that LPT1 uses the usual base address 12 19 RampRate Purpose Specify the source ramp
469. value takes precedence over the value defined by the toolbox 3 19 3 The Data Acquisition Session 3 20 If a property has a finite set of string values then the default value is enclosed by curly braces For example the default value for the LoggingMode property is Memory set ai LoggingMode Disk Memory Disk amp Memory You can also use the propinfo function or refer to Chapter 11 Base Property Reference or Chapter 12 Device Specific Property Reference to find the default value for any property The Data Acquisition Property Editor The Data Acquisition Property Editor is a graphical user interface GUI for accessing device object channel and line properties The GUI is designed so that you can e List all existing device objects as well as the channels or lines they contain e Configure property values e Display property characteristics e Display property help You open the editor with the daqpropedit function or via the Workspace browser by right clicking a device object and selecting Explore gt Call Property Editor from the context menu For example create the analog input object ai for a sound card and add both hardware channels ai analoginput winsound addchannel ai 1 2 Open the property editor from the command line daqpropedit ai Configuring and Returning Properties The Data Acquisition Property Editor is shown below File Options Help Lis
470. values and then reads back those values You should modify this example to suit your specific application needs If you want detailed information about reading and writing digital values refer to Chapter 7 Digital Input Output Create a device object Create the digital I O object dio for a National Instruments PCI 6024E board with hardware ID 1 dio digitalio nidaq 1 Add lines Add eight hardware lines to dio and configure them for output addline dio 0 7 out Read and write values Create an array of output values and write the values to the digital I O subsystem Note that reading and writing digital I O line values typically does not require that you configure specific property values pval 11110101 putvalue dio pval gval getvalue dio Accessing Your Hardware 4 Clean up When you no longer need dio you should remove it from memory and from the MATLAB workspace delete dio clear dio Note Digital line values are usually not transferred at a specific rate Although some specialized boards support clocked I O the Data Acquisition Toolbox does not support this functionality 2 Getting Started with the Data Acquisition Toolbox Understanding the Toolbox Capabilities In addition to the printed and online documentation the Data Acquisition Toolbox provides these resources to help you understand the product capabilities e The Contents M file e Documentation exampl
471. ve 4000 Hz which is the Nyquist frequency After you set the tuning fork vibrating and place it near the microphone you will trigger the acquisition one time using a manual trigger You can run this example by typing daqdoc4_1 at the MATLAB command line 1 Create a device object Create the analog input object AI for a sound card The installed adaptors and hardware IDs are found with daqhwinfo AI analoginput winsound 2 Add channels Add one channel to AI chan addchannel AI 1 3 Configure property values Assign values to the basic setup properties and create the variables blocksize and Fs which are used for subsequent analysis The actual sampling rate is retrieved because it might be set by the engine to a value that differs from the specified value duration 1 1 second acquisition set AI SampleRate 8000 ActualRate get AI SampleRate set AI SamplesPerTrigger duration ActualRate set AI TriggerType Manual blocksize get AI SamplesPerTrigger Fs ActualRate 4 Acquire data Start AI issue a manual trigger and extract all data from the engine Before trigger is issued you should begin inputting data from the tuning fork into the sound card start AI trigger AI data getdata AI 4 15 4 Getting Started with Analog Input 5 Clean up When you no longer need AI you should remove it from memory and from the MATLAB workspace delete AI clear AI
472. vice objects waittime The maximum time to wait for obj to stop running waittilstop obj waittime blocks the MATLAB command line and waits for obj to stop running You specify the maximum waiting time in seconds with waittime waittime overrides the value specified for the Timeout property If obj is an array of device objects then waittilstop might wait up to the specified time for each device object in the array waittilstop is particularly useful if you want to guarantee that the specified data is acquired before another task is performed If obj is not running when waittilstop is issued or if an error occurs while obj is running then waittilstop immediately relinquishes control of the command line When obj stops running its Running property is automatically set to Off obj can stop running under one of the these conditions e The requested number of samples is acquired analog input or sent out analog output e The stop function is issued e A run time error occurs e The Timeout property value is reached waittime supersedes this value It is not guaranteed that the StopFcn property is called before waittilstop returns The stop event is recorded by the EventLog property waittilstop Example See Also Create the analog input object ai for a National Instruments board add eight channels to it and configure a 25 second acquisition ai ch ai ai ai analoginput nidaq 1 addchannel ai 0 7
473. ware channels to it As shown by the figure in Adding Channels or Lines on page 3 8 you can think of a device object as a container for channels The collection of channels contained by the device object is referred to as a channel group As described in Mapping Hardware Channel IDs to MATLAB Indices on page 3 9 a channel group consists of a mapping between hardware channel IDs and MATLAB indices see below When adding channels to an analog output object you must follow these rules e The channels must reside on the same hardware device You cannot add channels from different devices or from different subsystems on the same device e The channels must be sampled at the same rate You add channels to an analog output object with the addchannel function addchannel requires the device object and at least one hardware channel ID as input arguments You can optionally specify MATLAB indices descriptive channel names and an output argument For example to add two hardware channels to the device object ao created in the preceding section chans addchannel ao 0 1 6 3 6 Analog Output 6 4 The output argument chans is a channel object that reflects the channel array contained by ao You can display the class of chans with the whos command whos chans Name Size Bytes Class chans 2x1 512 aochannel object Grand total is 7 elements using 512 bytes You can use chans to easily access channels For example you
474. with Analog Input 4 6 Alternatively you can use the ChannelName property ai InputType SingleEnded addchannel ai 0 15 ai Channel 1 ChannelName TrigChan You can now use the channel name to reference the channel ai TrigChan InputRange 10 10 Example Adding Channels for a Sound Card Suppose you create the analog input object ai for a sound card ai analoginput winsound Most sound cards have just two hardware channels that you can add If one channel is added the sound card is said to be in mono mode If two channels are added the sound card is said to be in stereo mode However the rules for adding these two channels differ from those of other data acquisition devices These rules are described below Mono Mode If you add one channel to ai the sound card is said to be in mono mode and the channel added must have a hardware ID of 1 addchannel ai 1 At the software level mono mode means that data is acquired from channel 1 At the hardware level you generally cannot determine the actual channel configuration and data can be acquired from channel 1 channel 2 or both depending on your sound card Channel 1 is automatically assigned the descriptive channel name Mono ai Channel ChannelName ans Mono Adding Channels to an Analog Input Object Stereo Mode If you add two channels to ai the sound card is said to be in stereo mode You can add two channels using two calls to add
475. with an analog input object you can preview the data with the peekdata function peekdata takes a snapshot of the most recent data but does not remove data from the engine For example to preview the most recent 500 samples acquired by each channel contained by ai data peekdata ai 500 Because previewing data is usually a low priority task peekdata does not guarantee that all requested data is returned You can preview data at any time while the device object is running However you cannot use peekdata in conjunction with hardware triggers because the device is idle until the hardware trigger is received Acquiring Data Logging Data While the analog input object is running you can log acquired data to the engine memory or to a disk file However before you can log data a trigger must occur You configure an analog input trigger with the TriggerType property For a detailed description of triggers refer to Configuring Analog Input Triggers on page 5 19 When the trigger occurs the Logging property is automatically set to On and data acquired from the hardware is logged to the engine or a disk file You extract logged data from the engine with the getdata function For example to extract all logged samples for each channel contained by ai data getdata ai getdata blocks the MATLAB command line until all the requested data is returned to the workspace You can extract data any time after the trigger occurs
476. x SampleRate 44100 Refer to Chapter 10 Function Reference to see which functions accept a device object array as an input argument Where Do Device Objects Exist When you create a device object it exists in both the MATLAB workspace and the data acquisition engine For example suppose you create the analog input object ai for a sound card and then make a copy of ai ai analoginput winsound newai ai The copied device object newai is identical to the original device object ai You can verify this by setting a property value for ai and returning the value of the same property from newai set ai SampleRate 22050 get newai SampleRate ans 22050 Creating a Device Object As shown below ai and newai return the same property value because they both reference the same device object in the data acquisition engine copy MATLAB ai m newai Data Acquisition Engine al If you delete either the original device object or a copy then the engine device object is also deleted In this case you cannot use any copies of the device object that remain in the workspace because they are no longer associated with any hardware Device objects that are no longer associated with hardware are called invalid objects The example below illustrates this situation delete ai newai newai Invalid Data Acquisition object This object is not associated with any hardware
477. y appears in myai mas ai StartFen startfcn1 and is saved in myai mat as startfcn1 mycallback 2 magic 10 To recreate ai and assign the device object to a new variable ainew ainew myai The associated MAT file myai mat is automatically loaded 10 77 peekdata Purpose Syntax Arguments Description Remarks 10 78 Preview most recent acquired data data peekdata obj samples obj An analog input object samples The number of samples to preview for each channel contained by obj data An m by n matrix where m is the number of samples and n is the number of channels data peekdata obj samples returns the latest number of samples specified by samples to data More About Using peekdata e Unlike getdata peekdata is a nonblocking function that immediately returns control to MATLAB Because peekdata does not block execution control data might be missed or repeated peekdata takes a snapshot of the most recent acquired data and does not remove samples from the data acquisition engine Therefore the SamplesAvailable property value is not affected when peekdata is called Rules for Using peekdata e You can call peekdata before a trigger executes Therefore peekdata is useful for previewing data before it is logged to the engine or to a disk file e In most cases you will call peekdata while the device object is running However you can call peekdata once after the device object s
478. y positive values are permitted If StopTriggerDelayUnits is set to Samples only integer values are allowed Properties StopTriggerDelayUnits StopTriggerType 12 31 StopTriggerDelayUnits Purpose Description Characteristics Values See Also 12 32 Specify the units in which the stop trigger delay is measured StopTriggerDelayUnits can be Seconds or Samples If StopTriggerDelayUnits is Seconds then data logging is delayed by the specified time for each channel group member If StopTriggerDelayUnits is Samples then data logging is delayed by the specified number of samples for each channel group member The stop trigger delay value is given by the StopTriggerDelay property Vendor Usage Access Data Type Read only when running Seconds Samples Properties StopTriggerDelay Keithley AO Channel Read write String Yes The trigger is delayed by the specified number of seconds The trigger is delayed by the specified number of samples StopTriggerType Purpose Specify the type of stop trigger to execute Description StopTriggerType can be None HwDigital or HwAnalog If StopTriggerType is HwDigital the acquisition stops on the rising or falling edge of the TGIN input line as defined by the StopTriggerCondition property If StopTriggerType is HwAnalog the acquisition stops when the channel specified by the StopTriggerChannel property meets the conditions defined by StopTriggerCondition a
479. y the associated display properties To specify a precise vertical scale or offset you modify the associated channel properties You can access these properties using the Scope Editor and the Channel Editor respectively You open these editors with the Edit menu or a right click menu Note that all displays use the same horizontal offset and scale 9 softscope The Data Acquisition Oscilloscope 9 12 Configuring Channel Properties There are two sets of properties associated with the Channel Scaling panel e Channel panel properties Properties associated with the controls and labels that make up the panel e Channel properties Properties associated with the hardware math and reference channels that are listed in the panel For descriptions of all channel properties click the Help button of the appropriate GUI editor Channel Panel Properties You can change the characteristics of the controls and labels that make up the panel with the Scope Editor GUI To open this GUI select Scope from the Edit menu choose the Scope Properties pane and select Channel Scaling from the Select scope components list box The Scope Properties pane is shown below x Scope Scope Properties Select the scope components display a display2 Triggers Channel Scaling Select Channel Scaling Edit the selected scope components properties HorizontalOffsetSensitivity 0 003 HorizontalScaleSensitivity 0 01 Name
480. ying a Toolbox Function as a Callback In addition to specifying your own callback function you can specify the start stop or trigger toolbox functions as callbacks For example to configure ai to stop running when an overrange condition occurs ai InputOverRangeFcn stop Examples Using Callback Properties and Functions This section provides examples that show you how to create callback functions and configure callback properties Displaying Event Information with a Callback Function This example illustrates how callback functions allow you to easily display event information The example uses daqcallback to display information for trigger run time error and stop events The default SampleRate and SamplesPerTrigger values are used which results in a 1 second acquisition for each trigger executed You can run this example by typing daqdoc5 6 at the MATLAB command line Events and Callbacks 1 Create a device object Create the analog input object AI for a sound card The installed adaptors and hardware IDs are found with daqhwinfo AI analoginput winsound AI analoginput nidaq 1 AI analoginput mcc 1 oe 2 Add channels Add one hardware channel to AI chan addchannel AI 1 chan addchannel AI 0 For NI and MCC 3 Configure property values Repeat the trigger three times find the time for the acquisition to complete and define daqcallback as the M file to execute when a trigger

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