Home

Data Acquisition Toolbox User's Guide

Contents

1. M Horiz Horiz Horizonta v Vet Vert Verica 0 jv Max max Horizonta v Min min Horizonta Iz Mean mean Horizonta Predefined measure ments M Pk2Pk peak2peak None M Freq frequency None Period period None v RMS ms Horizonta M STD std Horizonta Delete OK Cancel Apply Help 12 19 12 softscope The Data Acquisition Oscilloscope 12 20 Defining a Measurement Measurements that you define for the Oscilloscope are displayed in the Measurements pane By default this pane is not included as part of the Oscilloscope To create the pane you define one or more initial measurements There are two ways to do this Right click in the Channel Scaling pane and select Add Measurement from the menu Use the Measurement Editor GUI which you open by selecting the Edit gt Measurement menu item Alternatively you can create an empty Measurements pane 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 E x Measurement Measurement Properties Measurement Type r Define a new measurement Select the channel and Channel cHo xl the measurement type Type Vert z Add Click Add to add the measurement to the table Defined measurements Chan
2. NI USB devices that have their own power supply can shut down if the driver does not set the USB power correctly Note The Traditional NI DAQ adaptor will be deprecated in a future version of the toolbox If you create a Data Acquisition Toolbox object for Traditional NI DAQ adaptor beginning in R2008b you will receive a warning stating that this adaptor will be removed in a future release See the supported hardware page at www mathworks com products daq supportedio html for more information B Digilent Analog Discovery Devices Digilent Analog Discovery Devices B 4 In the session based interface you cannot use multiple Diligent devices in the same session If you need to use multiple devices add one device per session and start the sessions sequentially Digilent devices limit the minimum and maximum allowable rate of sampling based on channel types to Analog Input only 0 1 1 000 000 Analog Output only 4096 1 000 000 Input and Output 8192 300 000 Data Acquisition Toolbox conforms to the Digilent Player Mode for the Arbitrary Waveform Generator You cannot use background operations with Digilent devices You can only perform foreground operations using startForeground You cannot perform synchronous and triggered operations using a Digilent device in the session based interface You cannot access the digital input and output capabilities of a Digilent device Measurement Computing H
3. You can run this example by typing daqdoc5 1 at the MATLAB Command Window 1 Create a device object Create the analog input object AI for a sound card The available adaptors and hardware IDs are found with daghwinfo AI analoginput winsound AI analoginput nidaq Dev AI analoginput mcc 1 2 Add channels Add one hardware channel to AI addchannel AI 1 s amp addchannel AI 0 For NI and MCC 3 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 AI SampleRate AI SamplesPerTrigger duration ActualRate figure P plot zeros 1000 1 7 11 7 Doing More with Analog Input 7 12 T title sprintf Peekdata calls num2str 0 xlabel Samples axis O 1000 1 1 grid on 4 Acquire data Start AI and update the display for each 1000 samples acquired by polling SamplesAcquired The drawnow command forces the MATLAB workspace to update the plot Because peekdata is used all acquired data might not be displayed start AI i 1 while AI SamplesAcquired AI SamplesPerTrigger while AI SamplesAcquired 1000 i end data peekdata AI 1000 P ydata data T String sprintf Peekdata calls num2str i drawnow i i 1 end Make sure AI has stopped running before cleaning up the workspace wait AI 2
4. AI analoginput mcc 1 X ge Events and Callbacks 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 file daqdoc5 7plot every 0 5 seconds Note that the variables bsize P and T are passed to the callback function duration 10 Ten second duration AI SampleRate 22050 ActualRate AI SampleRate AI SamplesPerTrigger duration ActualRate 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 AI TimerFcn daqdoc5 7plot bsize P T Acquire data Start AI The drawnow command in daqdoc5_7plot forces MATLAB to update the display The wait function blocks the MATLAB Command Window and waits for AI to stop running start AI wait 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 7 51 7 Doing More with Analog Input Scaling Data Linearly 7 52 In this section Analog Input Engineering Units Properties on page 7 52 Perform Linear Conversion on page 7 53 Linear Conversion with Asymmetric Data on page 7 55 Analog Input Engineering Units Properties Data Acqui
5. 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 Reference Individual Hardware Lines on page 10 11 you can also access lines with the Line property 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 10 2 Descriptive Digital I O Line Properties Property Name Description HwLine Specify the hardware line ID Index Indicate the MATLAB index of a hardware line Parent Indicate the parent device object of a line Type Indicate a line You can display the values of these properties for hwlines with the get function hwlines HwLine Index Parent Type ans 0 1 1x1 digitalio Line 1 2 1x1 digitalio Line 2 3 1x1 digitalio Line 3 4 1x1 digitalio Line 4 5 1x1 digitalio Line 5 6 1x1 digitalio Line 6 7 1x1 digitalio Line 7 8 1x1 digitalio Line Line and Port Characteristics As described in the preceding section when you add lines to a DIO object they must be configured for either input or output You read values from an input line and write values to an output line Whether a given hardware line
6. 12 11 12 softscope The Data Acquisition Oscilloscope 12 12 Channel Editor xi Channel Channel Properties Channel Display r Define a new channel Te wath m Name Epessiom Display pat ss sz Add Defined channels m Type Ka Data Source Display M Ha rdware CH0 Hardware channel O display2 Hardware channel 1 display1 abs CH abs CH1 not displayed lt not displayed gt M Hardware CH1 l Reference r1 Clear the math and reference channels from the Oscilloscope Note that if you clear the check boxes then in addition to the channels not being displayed For hardware channels data is not streamed into the Oscilloscope For math and reference channels the values are not calculated Channel Data and Properties Channel Data and Properties In this section Scaling the Channel Data on page 12 13 Configuring Channel Properties on page 12 14 Scaling the Channel Data You can scale the defined channels using the Channel Scaling pane In particular you can modify The horizontal scaling and offset for all display components 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 b
7. 18 4 Acquire Non Clocked Digital Data 18 6 XV Acquire Clocked Digital Data with Imported Clock 18 7 Acquire Clocked Digital Data with Shared Clock 18 9 Acquire Digital Data Using Counter Channels 18 11 Generate a Clock Using a Counter Output Channel 18 11 Use Counter Clock To Acquire Clocked Digital Data 18 12 Acquire Digital Data in Hexadecimal Values 18 14 Control Stepper Motor using Digital Outputs 18 15 Generate Non Clocked Digital Data 18 20 Generate Signals Using Decimal Data Across Multiple II PL 18 21 Generate And Acquire Data On Bidirectional Channels 18 22 Generate Signals On Both Analog and Digital Channels 18 24 Output Digital Data Serially Using a Software Clock 18 25 Multichannel Audio Multichannel Audio Input and Output 19 2 Multichannel Audio Session Rate llle 19 2 Multichannel Audio Range 0 00000 ee eee 19 2 Acquire Multichannel Audio Data 00005 19 3 Generate Continuous Audio Data 005 19 4 Waveform Function Generation 20 Digilent Analog Discovery Devices xvi Contents Digilent Waveform Function Generation Channels 20 3 Waveform Types po eie Ede ves P s 20 6 Generate a Standard Waveform Using Waveform Function Generation Channels 0 0 00 cece 20 9 Generate an Arbitrar
8. 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 Extract 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 When you set the LoggingMode property to Memory or Disk amp Memory then engine stores all the data in memory until you extract it with getdata Manage Acquired Dota If you do not extract this data and the amount of data stored in memory reaches the limit for the data acquisition object see daqmem obj a DataMissed event occurs At this point the acquisition stops 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 1000 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
9. E In ara a a OQ TE qj Model Browser Analog Input Model Analog Input Model Pa Analog Input Model Aux Realte 8000 samples sec While the simulation is running the status bar at the bottom of the Simulink editor indicates the progress of the simulation If you are speaking into the microphone you will also see the live sound data plotted in the scope Step 8 Look at the Data in the Scope When the 20 seconds elapses the model stops running and you will have 20 seconds of sound data displayed by the scope Click the Autoscale toolbar button binoculars Build Models to Acquire Data icon in the scope to see the portion of the collected data that has the most contrast or significance It will look something like this ipi xi ajaan HERDAR Note in the above example that words were spoken into the microphone between the 7th and 8th second and only ambient sound is picked up between the 9th and 10th second 13 13 13 Using the Data Acquisition Blocks in Simulink In the following example you can see that the volume of the sound peaked around the 18th second when shouting was picked up by the microphone scope ox ajas AEREA R 13 14 Using the Session Based Interface About the Session Based Interface on page 14 2 Digital Input and Output on page 14 5 Discover Hardware Devices on page 14 6 Create a Session on page 14 8 14 Using the Ses
10. Sarrples x10 Return 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 Manage Acquired Dota 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 dij di din t1 doi doo don t2 dai dao dan ta dint dino dion tm 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 7 17 7 Doing More with Analog Input 7 18
11. 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 recording and retrieving events refer to Record and Retrieve Event Information on page 7 44 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 Configure Analog Input Triggers 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 Record and Retrieve Event Information on page 7 44 Device Specific Hardwa
12. ans analoginput winsound 0 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 enter ai analoginput winsound To create an analog output object for the sound card enter ao analogoutput winsound If you have CompactDAQ device or a counter timer device see Data Acquisition Session on page 3 2 Device Object Information To display hardware information for a specific device object you supply the device object as an argument to daghwinfo The hardware information for the analog input object ai created in the Adaptor Specific Information section is given below out daghwinfo ai out AdaptorName winsound Bits 16 Coupling AC Coupled DeviceName AudioPCI Record DifferentialIDs Gains ID O InputRanges 1 1 MaxSampleRate 44100 MinSampleRate 8000 NativeDataType int16 Polarity Bipolar 2 23 2 Using Data Acquisition Toolbox Software 2 24 SampleType SimultaneousSample SingleEndedIDs 1 2 SubsystemType AnalogInput TotalChannels 2 VendorDriverDescription Windows Multimedia Driver VendorDriverVersion 5 0 Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB Among other things this information tells you th
13. display2 Triggers Select Measurements Edit the selected scope components properties E Name Measurements ShowName FE True OK Cancel Help Measurement Properties You can configure measurement properties with the Measurement Properties editor You can open this editor two ways Right click menu Place the mouse cursor in the Measurements pane of interest right click and select Edit Properties from the menu 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 The Measurement Properties pane 1s shown below 12 23 12 softscope The Data Acquisition Oscilloscope Measurement Editor xi Measurement Measurement Properties Measurement Type Selectthe measurements Select the CHO peak to peak measurement CHO Vert Edit the selected measurements properties BufferSize 1000 Store 1000 measurements Color om DrawValueAlways p True Enabled pE True Expression peak2peak HorizontalAlignment gt left i Label SelectedColor zz VerticalAlignment top 12 24 Exporting Data
14. fgenCh Frequency 100e3 Set the session duration to 5 seconds and generate continuous data s DurationInSeconds 5 startForeground s Triggers and Clocks Trigger Connections on page 21 2 Clock Connections on page 21 5 2 Triggers ond Clocks Trigger Connections 21 2 In this section When to Use Triggers on page 21 2 External Triggering on page 21 3 Acquire Voltage Data Using a Digital Trigger on page 21 4 When to Use Triggers Use triggers to simultaneously start all devices in the session You connect a trigger source to a trigger destination A trigger source can be either external where the trigger comes from a source outside a session or on a device and terminal pair within a session Trigger destination devices can be external where the signals are received outside the session or devices within the session To understand source and destination devices see Source and Destination Devices on page 22 5 Note You can have multiple destinations for your trigger but only one source Trigger Connections Data Acquisition Session Trigger destinations Trigger source Note You cannot use trigger and clock connections with audio channels External Triggering You can configure devices in a session to receive an external trigger To use an external trigger source your connection parameters must correctly specify the exact device
15. Dev1 8 31 8 Analog Output 8 32 5AO analogoutput mcc 1 Add channels Add one channel to AO chan addchanne1 A0 1 chan addchannel AO 0 For NI and MCC Configure property values Specify daqdoc6_5disp as the 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 AO SampleRate 8000 ActualRate AO SampleRate AO StartFcn daqdoc6 5disp AO TriggerFcn daqdoc6_5disp AO StopFcn daqdoc6 5disp data sin linspace 0 2 pi 500 ActualRate data data data data time length data AO SampleRate putdata AO0 data Output data Start AO The wait function blocks the MATLAB Command Window and waits for AO to stop running start AO0 wait AO 5 Clean up When you no longer need AO you should remove it from memory and from the MATLAB workspace delete A0 clear AO Scale Data Linearly Scale Data Linearly In this section Engineering Units on page 8 33 Perform a Linear Conversion on page 8 34 Engineering Units Data Acquisition Toolbox software 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 da
16. S daq createSession ni 23 9 23 Transition Your Code to Session Based Interface 23 10 addAnalogOutputChannel s Dev i ao0 Voltage 2 Setthe session rate to 8000 s Rate 8000 3 queue some output data queueOutputData s zeros 10000 1 4 Start the acquisition and issue a wait to block MATLAB for 16 seconds If the operation does not complete in 2 seconds a timeout occurs startBackground s s wait 2 Count Pulses You can count pulses to clock your data acquisition Legacy Interface You cannot use counter input and output channels using the legacy interface You can use the analog input subsystem s internal clock to create a threshold and look for consecutive samples that are on opposite sides of the threshold This will give you results similar to using a counter input channel ai analoginput nidaq addchannel ai 1 threshold 3 5 offsetData data 2 end NaN risingEdge find data lt threshold amp offsetData gt threshold fallingEdge find data threshold amp offsetData threshold Session Based Interface Count edges of a pulse using a counter input channel on your device Ss createSession ni addCounterInputChannel s Dev i ctrO EdgeCount inputSingleScan s Troubleshooting Your Hardware This appendix describes simple tests you can perform to troubleshoot your data acquisition hardware The tests involve using software provided by the ve
17. You can specify the measurement range of an analog input subsystem Legacy Interface 1 Create the analog input object ai for a National Instruments device and add two channels to it ai analoginput nidaq Dev1 addchannel ai 0 1 Configure both channels to accept input signals between 10 volts and 10 volts 23 7 23 Transition Your Code to Session Based Interface 23 8 ai Channel InputRange 10 10 Session Based Interface 1 Create a session and add an analog input channel S daq createSession ni ch addAnalogInputChannel s Devi aii Voltage 2 Change the range to 10 to 10 volts ch Range 10 10 Fire an Event When Number of Scans Exceed Specified Value You can specify your acquisition to watch for a specified number of scans to occur and fire an event if the acquisition exceeds the specified number Legacy Interface You can use the Buff eringConfig property to specify allocated memory for a specified channel If the number of samples acquired exceeds the allocated memory then an error 1s returned 1 Create an analog input object ai for a National Instruments device and add a channel to it ai ch 2 Setthe rate to 800 000 analoginput nidaq Dev i addchannel ai 0 oil ai SampleRate 800000 3 Set the buf feringConfigMode to Manual and set the bufferingConfig to ai bufferingConfigMode Manual ai bufferingConfig 512 30 Session Based In
18. 0 llle 12 3 xii Contents Displaying Channels ll nee 12 5 Creating a Display llle 12 5 Creating Additional Displays 0 00005 12 6 Configuring Display Properties llle 12 7 Math and Reference Channels 0 0005 12 8 Removing Channel Displays 0005 12 11 Channel Data and Properties 04 12 13 Scaling the Channel Data lessen 12 13 Configuring Channel Properties llle 12 14 Triggering the Oscilloscope 0 000005 12 16 Acquisition Types 0 0 0 0 eens 12 16 Trigger Types fic 40s ROME S Giada Saha ee RES 12 16 Configuring Trigger Properties 0 0000 u ee 12 17 Making Measurements 0 000 c eee neces 12 19 Predefined Measurement 0000 c eee ene 12 19 Defining a Measurement llle 12 20 Defining a New Measurement Type 12 21 Configuring Measurement Properties 12 22 Exporting Data 0 00 0c eee 12 25 Channels 2 22115 2210 oie yaad hw uide eese OD week hoes he cules 12 25 Measurements 0 cece eee eee eee 12 26 Saving and Loading the Oscilloscope Configuration 12 27 Using the Data Acquisition Blocks in Simulink 13 Data Acquisition Simulink Blocks Basics 13 2 Open the Data Acquisition Block Library 13 3 Use the daqlib Command from the MATLAB Workspace 13 3
19. 1 1 Multichannel Audio Input and Output Acquire Multichannel Audio Data This example shows how to acquire audio data for seven seconds and plot the data Discover audio devices installed on your system and create a session for DirectSound devices d daq getDevices S daq createSession directsound Il Add two audio input channels for the microphone with id Audio1 Make sure that a microphone is plugged into the appropriate jack addAudioInputChannel s Audioi 1 2 Set the session to run for 7 seconds and play an audio segment for the microphone to pick up s DurationInSeconds 7 Acquire data in the foreground and plot the data versus time data t startForeground s plot t data 19 3 9 Multichannel Audio Generate Continuous Audio Data This example shows how to set up a continuous audio generation This example uses but does not require a 5 1 channel sound system In this example you generate data using the sound card on your computer using a 5 1 channel speaker setup Before you begin verify that your environment is set up 19 4 Multichannel Audio Input and Output so that you can generate data with your sound card For more information refer to Troubleshooting in Data Acquisition Toolbox Load audio data Load an audio file containing a sample of Handel s Hallelujah Chorus load handel Plot audio data Plot data in order to identify five distinct segments
20. 6 x 5 o In 7 6 0 aa Wg i 8 v 7 0 In You can use the Line property to display only the line summary information DIO Line 10 23 Saving and Loading Save and Load Device Objects on page 11 2 Log Information to Disk on page 11 5 11 Saving and Loading Save and Load Device Objects 11 2 In this section Save Device Objects to a File on page 11 2 Save Device Objects to a MAT File on page 11 3 Save Device Objects to a File Note For analog input objects you can also save acquired data hardware information and so on to a log file Refer to Log Information to Disk on page 11 5 for more information You can save a device object to a file using the obj2mfile function obj 2mfile provides you with these options Save all property values or save only those property values that differ from their default values 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 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 dev
21. MATLAB and Simulink for immediate analysis You can also send out data over analog and digital output channels provided by data acquisition hardware The toolbox s data acquisition software includes functions for controlling analog input analog output counter timer and digital I O subsystems of a DAQ device You can access device specific features and synchronize data acquired from multiple devices You can analyze data as you acquire it or save it for post processing You can also automate tests and make iterative updates to your test setup based on analysis results Simulink blocks included in the toolbox let you stream live data directly into Simulink models enabling you to verify and validate your models against live measured data as part of your design verification process Key Features Support for a variety of industry standard data acquisition boards and USB modules Support for analog input analog output counters timers and digital I O Direct access to voltage current IEPE accelerometer and thermocouple measurements Live acquisition of measured data directly into MATLAB or Simulink Hardware and software triggers for control of data acquisition Device independent software interface Product Capobilities Product Capabilities In this section Understanding Data Acquisition Toolbox on page 1 3 Exploring the Toolbox on page 1 4 Supported Hardware on page 1 5 Understandin
22. Note The Traditional NI DAQ adaptor will be deprecated in a future version of the toolbox If you create a Data Acquisition Toolbox M object for Traditional NI DAQ adaptor beginning in R2008b you will receive a warning stating that this adaptor will be removed in a future release See the supported hardware page at www mathworks com products daq supportedio html for more information You can return the line and port characteristics with the daqhwinfo function For example National Instruments USB 6281 board has three ports with eight lines per port To return the digital I O characteristics for this board hwinfo daqghwinfo dio Display the line characteristics for each port hwinfo Port 1 ans ID O LineIDs 0 123 45 6 7 Direction in out Add Lines to Digital I O Objects Config port hwinfo Port 2 ans ID 2 LineIDs 0 123 45 6 7 Direction in out Config port hwinfo Port 3 ans ID 3 LineIDs 0 123 4 5 6 7 Direction in out Config port This information tells you that you can configure all 24 lines for either input or output and that the 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
23. Session Based Interface Using National Instruments Devices Data acquisition devices index Vendor Device ID Description 1 ni cDAQ1Mod1 2 ni cDAQ1Mod7 3 ni cDAQ2Mod1 4 ni cDAQ2Mod2 5 ni cDAQ2Mod3 6 ni cDAQ2Mod4 7 ni cDAQ2Mod5 8 ni cDAQ2Mod6 9 ni cDAQ2Mod7 10 ni cDAQ2Mod8 11 ni Dev2 12 ni Dev3 13 ni Dev4 14 ni Dev5 15 ni Dev6 16 ni Dev8 Device currently not National Instruments National Instruments National Instruments National Instruments National Instruments National Instruments National Instruments National Instruments National Instruments National Instruments National Instruments National Instruments National Instruments National Instrument National Instruments National Instrument supported See docume PCIe 6363 USB 6255 USB 9233 S PCI 6601 PCI 6220 S PCI 6509 ntation on Unsupported Devices for more information e Make sure that your network device is not reserved and not disconnected Go to the Supported Hardware area in Data Acquisition Toolbox page on the MathWorks website for a list of supported devices Network Devices Appears with an Asterisk If your network device appears as unsupported or unavailable make sure that the device is connected and reserved in National Instruments Measurement and Automation Explorer Issue daq reset to reset devices settings Ifyou see this timeout error when communicating with a network device Network timeout error while commu
24. Use the Simulink Library Browser Lun 13 4 Build Models to Acquire Data 005 13 6 Data Acquisition Toolbox Block Library 13 6 Bring Analog Data into a Model 005 13 6 xiii Using the Session Based Interface 14 About the Session Based Interface 14 2 Working with Sessions llle 14 2 Session Based Interface and Data Acquisition Toolbox 14 4 Digital Input and Output 0 0 0 eee 14 5 Discover Hardware Devices 00000 eee 14 6 Create a Session i29 gh Rte ak nl hn PLE RRUNE VE 14 8 Support Package Installer 15 Install Digilent Device Support 15 2 Install Multichannel Audio Device Support 15 4 Install National Instruments Device Support 15 6 NIDAQmx Driver Requirements 0000005 15 6 Install Support Package 0 0 0 eee eee ees 15 6 Session Based Analog Input and Output 16 Acquire Analog Input Data 0 aaaea 16 2 Using addAnalogInputChannel lille 16 2 Acquire Data in the Foreground 0 000005 16 2 Acquire Data from Multiple Channels 16 4 Acquire Data in the Background 00 005 16 5 Acquire Data from an Accelerometer 00 16 6 Acquire Bridge Measurements 000000 ee eee 16 9 Acquire Sound Pressure Data 0 0 00 0c c
25. 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 There are two kinds of software Driver software Application software For example suppose you are using Data Acquisition Toolbox software 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 1 17 T introduction to Data Acquisition 1 18 You Application Data Acquisition Toolbox software amp software MATLAB technical computing environment 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 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 Bring data on to and get data off of the board Control the rate at which data is acquired Integrate the data acquisition hardware with computer resources such as processor interrupts DMA and memory Integrate the data acquisition hardware with signal conditioning hardware Access multiple subsystems on a given data acquisition board Access mu
26. 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 Thesamples 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 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 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
27. callback function Stop Event A stop event is generated immediately after the device object and hardware device stop running This occurs when The stop function is issued The requested number of samples is acquired Arun 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 7 43 7 Doing More with Analog Input 1 44 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 1s significantly slowed or if the TimerPeriod value is too small There can only be one timer event waiting in the queue at a given time The callback function must process all available data to ensure that it keeps up with the inflow of data Alternatively you can use the SamplesAcquiredFcn analog input or SamplesOutputFocn analog output property to process the data when a specified number of samples is acquired Trigger Event A trigger event is generated immediately after a trigger occurs This event executes the callback function specified for the TriggerFcn property Under most
28. 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 A MEX file shared library 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 obje
29. on page 6 9 Trigger Types on page 6 11 Samples to Acquire per Trigger on page 6 12 Analog Input Basic Properties After hardware channels are added to the analog input object you should configure property values As described in Configure and Return Properties on page 4 14 Data Acquisition Toolbox software 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 control 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 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 Sampling Rate You control the rate at which an analog input subsystem converts analog data to digital data with the SampleRate prope
30. timing slot of the chassis Counters Restart When You Call Prepare Counters stop running in the background when you call prepare to perform clocked operations This operation resets counters and restarts them when the new operation starts Cannot Get Correct Scan Rate with Digilent Devices The scan rate when you use a Digilent device can be limited by the hardware s buffer size See Digilent Analog Discovery Devices on page B 4 for more information on maximum and minimum allowable rates Cannot Simultaneously Acquire and Generate with myDAQ Devices You cannot acquire and generate synchronous data using myDAQ devices because they do not share a hardware clock If you have both input and output channel s in a session and you start the session you will see near simultaneous acquisition and generation See Automatic Synchronization on page 22 6 for more information A 13 Session Based Interface Using National Instruments Devices A 14 Counter Single Scan Returns NaN An input single scan on counter input channels may return a NaN If this occurs make sure that the signal voltage complies with TTL voltage specifications Make sure that the channel frequency is within the specified frequency range External Clock Will Not Trigger Scan Adding an external clock to your session may not trigger a scan unless you set the session s rate to match the expected external clock frequency Why Does My S PDIF Device Time
31. 0 2 volt duration 2 AlVoice SampleRate 44100 ActualRate AlIVoice SampleRate AlVoice SamplesPerTrigger ActualRate duration AlVoice TriggerChannel chan AlVoice TriggerType Software AlVoice TriggerCondition Rising AlVoice TriggerConditionValue 0 2 4 Acquire data Start AIVoice 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 wait AIVoice durationt1 data time getdata AIVoice 1000 7 23 7 Doing More with Analog Input 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 5 Clean up When you no longer need AIVoice you should remove it from memory and from the MATLAB workspace delete AIVoice clear AIVoice 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 Actvaton 03 RI BREL IDOL C ITI I E A N BELLI yy torres ILI o Signal Level Volts 03 pee em HMM 0 0 005 001 0015 002 0025 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
32. 168E Series board Hardware Analog Triggering If TriggerType is HvAnalogPin 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 1s between 4 volts and 4 volts ai analoginput nidaq Dev addchannel ai 0 7 ai TriggerType HwAnalogPin ai TriggerCondition InsideRegion 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 channel The following example illustrates how to configure such a trigger where the trigger channel is assigned the descriptive name TrigChan and the default TriggerCondition property value is used ai analoginput nidaq Dev addchannel ai 0 7 ai Channel 1 ChannelName TrigChan ai TriggerChannel ai Channel 1 ai TriggerType HwAnalogChannel ai TriggerConditionValue 0 2 The diagram below illustrates how you can connect an analog trigger signal to an MIO 16E Series board 7 39 7 Doing More with Analog Input Analog pin PFIO TRIG1 MIO 16E Series board 7 40 Events and Callbacks Events and Callbacks In this section Events and Callbacks Basics on page 7 41 Event T
33. 1s shown here Data Acquisition Session Application Software Driver Software Driver For more information about creating sessions see Create a Session on page 14 8 3 3 3 Introduction to the Session Based Interface Choose the Right Interface Data Acquisition Toolbox supports the use of two interfaces The legacy interface and the session based interface Use this table to chose an interface based on your device type If you are using National Instruments devices see National Instruments Usage Based on Functionality Interface By Device Vendor Device Vendor National Instruments Session Based Interface Legacy Interface 32 bit MATLAB 4 64 bit MATLAB Digilent Analog Discovery 32 bit MATLAB 64 bit MATLAB DirectSound 32 bit MATLAB 64 bit MATLAB Measurement Computing 32 bit MATLAB 64 bit MATLAB Winsound 32 bit MATLAB 64 bit MATLAB Advantech 32 bit MATLAB 64 bit MATLAB Data Translation 32 bit MATLAB 64 bit MATLAB 3 4 Choose the Right Interface Device Vendor Session Based Interface Legacy Interface Other Vendors 32 bit MATLAB Y 64 bit MATLAB a You can install 32 bit MATLAB on a 64 bit Windows system For more information see this technical solution b For a complete list of supported vendors see the Supporte
34. 2 21 Adaptor Specific Information llle sn 2 22 Device Object Information 0 0 0 0 eee 2 23 Getting Help hag SS Ie BER a Le BASTA 2 25 The daghelp Function llle 2 25 The propinfo Function sleseee es 2 25 Introduction to the Session Based Interface 3 Data Acquisition Session uaaa aaaea 3 2 Choose the Right Interface llle els 3 4 Getting Help 4535 26 he ack Fis be EI aa e e Lene 3 7 Command Line Help 0 0 0 0c cece ee eee 3 7 Online Help ye etek eR Sh as ee ee ea e 3 7 Session Based Interface Examples 4 3 7 Data Acquisition Workflow 4 Understanding the Data Acquisition Workflow 4 2 OVerview ucc i he the soon Ma Pree ee Lap S 4 2 Real Time Data Acquisition 0 0000 e ee eee 4 3 Data Acquisition Workflow 000000 e eee 4 4 Create a Device Object 0 0000 cece eee 4 6 Understanding Device Objects 0 0 0 00 02 aes 4 6 Create an Array of Device Objects 00005 4 7 Where Do Device Objects Exist 0 000 000 5 4 8 Hardware Channels or Lines 0 4 10 Add Channels and Lines llle 4 10 Hardware Channel IDs to the MATLAB Indices 4 11 Configure and Return Properties 4 14 O Ver VIOW a s Etui CE er deep d pde RR eal er a Dac NU cx 4 14 Property Types llelelee e 4 14 Retu
35. 200 kHz and define a two second acquisition duration 2 ActualRate setverify AI SampleRate 200000 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 InputRange is set to the value that most closely encompasses the expected data range of 200 mV chan InputRange 0 5 0 5 4 Acquire data Start the acquisition and wait before acquiring data start AI wait AI duration 1 Extract and plot all the acquired data data getdata AI subplot 2 1 1 plot data Scaling Data Linearly Calculate and display the frequency information Fs ActualRate blocksize duration ActualRate f mag daqdocfft data Fs blocksize subplot 2 1 2 plot f mag 5 Clean up When you no longer need AI you should remove it from memory and from the MATLAB workspace delete AI clear AI Linear Conversion with Asymmetric Data The properties related to engineering units provide a way for Data Acquisition Toolbox software to convert raw measurement data into its original values and units SensorRange is the output voltage range that your sensor is capable of producing UnitsRange is the range of real world values physical phenomena that your sensor is measuring In many cases it is appropriate to set InputRange SensorRange and UnitsRange to the same values However if
36. 4 ni cDAG1Mod4 National Instruments NI 9201 5 ni cDAG1Mod5 National Instruments NI 9402 6 ni cDAG1Mod6 National Instruments NI 9213 7 ni cDAG1Mod7 National Instruments NI 9219 8 ni cDAG1Mod8 National Instruments NI 9265 9 ni Dev1 National Instruments PCIe 6363 10 ni Dev2 National Instruments NI ELVIS II This example uses a National Instruments amp ELVIS II with ID Dev2 Verify that its digital subsystem supports the OutputOnly measurement type devices 10 ans ni National Instruments NI ELVIS II Device ID Dev2 Analog input subsystem supports 7 ranges supported 18 15 18 session Based Digital Operations Rates from 0 0 to 1250000 0 scans sec 16 channels aiO ai 15 Voltage measurement type Analog output subsystem supports 5 0 to 5 0 Volts 10 to 10 Volts ranges Rates from 0 0 to 2857142 9 scans sec 2 channels ao0 ao1 Voltage measurement type Digital subsystem supports 39 channels portO lineO port2 line6 InputOnly OutputOnly Bidirectional measurement types Counter input subsystem supports Rates from 0 1 to 80000000 0 scans sec 2 channels ctrO ctr1 EdgeCount measurement type Counter output subsystem supports Rates from 0 1 to 80000000 0 scans sec 2 channels ctrO ctr1 PulseGeneration measurement type Hardware Setup Description This example uses a Portescap 20M020D1U 5V 18 Degree Unipolar Stepper Motor The TTL signals produced by the digital I O
37. 6363 10 ni Dev2 National Instruments NI ELVIS II ans ni National Instruments NI 9234 Device ID cDAQ1Mod3 Analog input subsystem supports 5 0 to 5 0 Volts range Rates from 1000 0 to 51200 0 scans sec 4 channels ai0 aii ai2 ai3 Voltage Accelerometer Microphone IEPE measurement types This module is in slot 3 of the cDAQ 9178 chassis with the name cDAQ1 Add an Accelerometer Channel Create a session and add an analog input channel with the Accelerometer measurement type S daq createSession ni addAnalogInputChannel s cDAQiMod3 0 Accelerometer Set Session Rate and Duration Change the scan rate to 4000 scans per second and the duration to 30 seconds s Rate 4000 s DurationInSeconds 30 S 16 7 16 Session Based Analog Input and Output 16 8 S Data acquisition session using National Instruments hardware Will run for 30 seconds 120000 scans at 4000 scans second Number of channels 1 index Type Device Channel MeasurementType Range Name 1 ai cDAQ1Mod3 aiO Accelerometer Diff 5 0 to 5 0 Volts Set Sensitivity You must set the Sensitivity value to the value specified in the accelerometer s data sheet This example uses a ceramic shear accelerometer model 352C22 from PCB Piezotronics is used with 9 22 mV per Gravity s Channels 1 Sensitivity 0 00922 s Channels 1 ans Data acquisition analog input accelerometer channel aiO on device cDAQiMod3 Se
38. Data Acquisition Toolbox object for Traditional NI DAQ adaptor beginning in R2008b you will receive a warning stating that this adaptor will be removed in a future release See the supported hardware page at www mathworks com products daq supportedio html for more information Support for the Parallel adaptor will be removed in a future version of the toolbox If you create a Data Acquisition Toolbox object for parallel beginning in R2008b you will receive a warning stating that this adaptor will be removed in a future release See the supported hardware page at www mathworks com products daq supportedio html for more information Note Additional vendors not in this table are listed in the supported hardware page at www mathworks com products daq supportedio html This page contains a comprehensive list of vendors whose hardware the toolbox supports and it provides information on how to obtain an adaptor As described in Examining Your Hardware Resources you can list the installed adaptor names with the daghwinfo function Toolbox Components Unsupported Hardware Refer to the supported hardware page for Data Acquisition Toolbox software at www mathworks com products daq supportedio html for the list of vendors whose hardware the toolbox supports and for information about how to obtain an adaptor If the device you are using is not listed on this page you can do one of the following Contact the device vendor to r
39. Data with a Sound Card Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB 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 Analog Input Examples Data Source Sensor Sound Card Data Sink Configure 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 above 4000 Hz which 1s 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 Window 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 winsoun
40. Documentation by the federal government or other entity acquiring for or through the federal government and shall supersede any conflicting contractual terms or conditions If this License fails to meet the government s needs or is inconsistent in any respect with federal procurement law the government agrees to return the Program and Documentation unused to The MathWorks Inc Trademarks MATLAB and Simulink are registered trademarks of The MathWorks Inc See www mathworks com trademarks for a list of additional trademarks Other product or brand names may be trademarks or registered trademarks of their respective holders Patents MathWorks products are protected by one or more U S patents Please see www mathworks com patents for more information Revision History May 1999 November 2000 June 2001 July 2002 June 2004 October 2004 March 2005 September 2005 October 2005 November 2005 March 2006 September 2006 March 2007 May 2007 September 2007 March 2008 October 2008 March 2009 September 2009 March 2010 September 2010 April 2011 September 2011 March 2012 September 2012 March 2013 September 2013 March 2014 October 2014 March 2015 September 2015 First printing Second printing Third printing Online only Online only Online only Online only Online only Reprint Online only Fourth printing Online only Online only Fifth printing Online only Online only Online only Online only Online only Online on
41. Help os Channel Scaling Triggers Horizontal Acquire Jone Shot x CHI Offset Scale Samples to acquire r C Fillthe display Count fon Vertical CH1 Offset Scale Type dependent gt Channel CHO m Condition Rising v vauet 33 Valuez p Pretrigger 0 02 sec p7 30Vidiv 5 0037 msidiv On Trigger Trigger level Pretrigger data Configure a one shot indicator indicator dependent trigger CHO 2 When you use a dependent trigger type the display associated with the selected channel contains these two indicators The trigger level on the vertical axis 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 that you can change the indicator locations graphically by placing the mouse cursor over the indicator and sliding it to the desired location Configuring Trigger Properties You can change the characteristics of the labels associated with the Triggers pane with the Scope Editor GUI To open this GUI select Scope from the Edit menu choose the 12 17 12 softscope The Data Acquisition Oscilloscope Scope Properties pane and select Triggers from the Select the scope components list box The Sc
42. ID 0 and 1 S daq createSession ni addAnalogInputChannel s cDAQiMod1 0 1 Voltage Add an additional channel on a separate device cDAQ1Mod6 with channel ID 0 For NI devices use either a terminal name like ai0 or a numeric equivalent like 0 Store this channel in the variable ch ch addAnalogInputChannel s cDAQ1Mod6 aiO Voltage ch Data acquisition analog input channel aiO on device cDAQ1Mod 16 Coupling DC InputType Differential Range 10 to 10 Volts Name empty ID aiO Device 1x1 daq ni CompactDAQModule ADCTimingMode View the session object to see the three channels s s Data acquisition session using National Instruments hardware Will run for 1 second 1000 scans at 1000 scans second Number of channels 3 index Type Device Channel MeasurementType Range Name 1 ai cDAQ1Mod1 aiO Voltage SingleEnd 10 to 10 Volts 2 ai cDAQ1Mod1 ail Voltage SingleEnd 10 to 10 Volts 3 ai cDAQ1Mod6 aiO Voltage Diff 10 to 10 Volts Acquire the data and store it in the variable data and plot it Acquire Analog Input Dota data startForeground s plot data Change the properties of the channel ai0 on cDAQ1Mod6 and display ch ch InputType SingleEnded ch Name Velocity sensor ch ch Data acquisition analog input channel aiO on device cDAQ1Mod6 Coupling DC InputType SingleEnded Range 10 to 10 Volts Name Velocity sensor ID aiO De
43. PXIiSlot3 0 Voltage Acquire data in the foreground without synchronizing the channels data time startForeground s plot time data The data returned is not synchronized Synchronize the two channels using the AutoSyncDSA property s AutoSyncDSA true Acquire data in the foreground and plot it data time startForeground s Synchronize DSA Devices plot time data The data is now synchronized PCI DSA Devices PCI devices are synchronized use the RTSI cable You can automatically synchronize these device series both homogeneously within the same series and heterogeneously across separate series in the same session when they are connected with a RTSI cable PCI 446x series PCI 447x series Note If you are synchronizing PCI devices make sure you register the RTSI cables in Measurement and Automation Explorer For more information see the NI knowledge base article What is RTSI and How is it Configured Document ID 2R5FK53J Synchronize DSA PCI Devices This example shows how to acquire synchronized data from two DSA PCI devices NI PCI 4461 and NI PCI 4462 Connect the two devices with a RTSI cable Register your RTSI cable in Measurement and Automation Explorer Create an acquisition session and add one voltage analog input channel from each of the two PXI devices S daq createSession ni addAnalogInputChannel s Devi 0 Voltage addAnalogInputChannel s Dev2
44. Set the rate of your session to the expected rate of your external scan clock s Rate 1000 Note Importing an external clock does not automatically set the rate of your session Manually set the session s rate to match the expected external clock frequency Add an external scan clock to your device on terminal PFI9 For more information see Terminals property addClockConnection s External Dev1 PFI9 ScanClock ans 18 7 18 session Bosed Digital Operations Scan Clock is provided externally and will be received by Dev i at terminal PFI9 Source External Destination Dev1 PFI9 Type ScanClock Acquire clocked data and plot it dataIn startForeground s plot dataIn Related Examples 2 Acquire Clocked Digital Data with Shared Clock on page 18 9 3 Acquire Digital Data Using Counter Channels on page 18 11 18 8 Acquire Clocked Digital Data with Shared Clock Acquire Clocked Digital Data with Shared Clock This example shows how to share the clock with the analog input subsystem on your device with the digital subsystem and acquire automatically synchronized clocked data You do not need any physical connections to share the clock For information on automatic synchronization see Automatic Synchronization Key DAQ Session Internal connection Analog input External wiring output subsystem External digital circuit Digital subsystem Create a session and
45. Setup on page 1 6 Calibration on page 1 6 Trials on page 1 7 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 Anatomy of a Data Acquisition Experiment 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 pre
46. Synchronization Data Acquisition Session Trigger or clock destinations Trigger Source CompactDAQ chassis 22 4 Source and Destination Devices Source and Destination Devices A source device and terminal pair generates the synchronization signal and is connected to the destination device and terminal pairs You must physically connect the source and destination terminals unless they are internally connected Check your device specifications for more information Synchronization connections are added from the source device to one or more destination devices The source device provides the trigger or clock signals The destination device receives a trigger or clock signal For example if you determine that a terminal on Dev1 will provide a trigger and a terminal on Dev2 will receive that signal then Dev1 becomes your source device and Dev2 your destination device You can have multiple destinations for your trigger and clock connections but only one source 22 5 22 Session Based Synchronization Automatic Synchronization 22 6 A session automatically starts all devices at the same time when you start an operation in most cases You must configure them to start synchronously when devices are not on a single chassis and do not share a clock If you have not configured synchronization on such devices the start operation reduces the latency between devices running them very close together to achieve near
47. The RSE configuration is used for floating signal sources In this case the hardware device itself provides the reference ground for the input signal 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 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 in first out FIFO buffer 1 29 T introduction to Data Acquisition 1 30 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 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
48. 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 next Analog Input Subsystem 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 of an S H circuit follows these steps 1 At a given sampling instant the switch connects the buffer and capacitor to an input 2 The capacitor is charged to the input voltage The charge is held until the A D converter digitizes the signal 4 For multiple channels connected multiplexed to one A D convert
49. Toolbox Capabilities In this section Contents File on page 2 19 Documentation Examples on page 2 19 Examples on page 2 20 Contents File The Contents file lists the toolbox functions and examples 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 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 files You can list all Data Acquisition Toolbox examples by typing help daqdemos All documentation example files begin with daqdoc To run an example type the file name at the command line Note that most analog input AT 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 AO subsystem of your hardware device does not have an onboard clock then these examples will not work To use the documentation examples you can Input single values using th
50. You Measure on page 1 32 Accuracy and Precision on page 1 32 Noise on page 1 36 Matching the Sensor Range and A D Converter Range on page 1 37 How Fast Should a Signal Be Sampled on page 1 37 What Do You Measure 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 Maximize the precision and accuracy Minimize the noise Match the sensor range to the A D range Accuracy and Precision Whenever you acquire measured data 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 measurem
51. a 4 dio Dev1 porti linei Bidirectional Unknown n a Set the direction on all channels to output data for i 1 4 s Channels i Direction Output end Generate digital data outputSingleScan s 1 0 1 0 Change the direction on all channels to input data for i 1 4 Generate And Acquire Data On Bidirectional Channels s Channels i Direction Input end Acquire digital data inputSingleScan s ans 1 0 1 0 You can also use the MATLAB deal function to change direction on all channels together s channels Direction deal Input 18 23 18 session Based Digital Operations Generate Signals On Both Analog and Digital Channels 18 24 This example shows how to generate signals when the session contains both analog and digital channels Find devices connected to your system and find the ID for NI 6255 d daq getDevices d Data acquisition devices index Vendor Device ID Description 1 ni Dev1 National Instruments USB 6255 2 ni Dev2 National Instruments USB 6363 Create a session and add two digital lines from port 0 on Dev1 S daq createSession ni addDigitalChannel s Devi PortO LineO 1 OutputOnly Data acquisition session using National Instruments hardware Clocked operations using startForeground and startBackground are disabled Only on demand operations using inputSingleScan and outputSingleScan can be done Number of channels 2 index Type Device Channel Measurem
52. a 64 bit MATLAB For this example analysis consists of finding the frequency components of the tuning fork and plotting the results To do so the function daqdocf ft 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 dagdocfft data Fs blocksize dagdocfft 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 og oe Analog Input Examples xfft abs fft data Avoid taking the log of O index find xfft 0 xfft index 1e 17 mag 20 10g10 xfft mag mag 1 floor blocksize 2 f 0 length mag 1 Fs blocksize f F 5 The results are given below plot f mag grid on ylabel Magnitude dB xlabel Frequency Hz title Frequency Components of Tuning Fork Frequency Components of Turing Fork Magnitude dB 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 6 19 6 Getting Started with Analog Input 6 20 maxfreq maxfreq 441 f maxindex The answer is 441 H
53. a Be ie ble es eR qe a ee 2G aS 6 9 rigger Types esist ue e ates Gite ERSTES E EE 6 11 Samples to Acquire per Trigger 00 000 eae 6 12 Acquire Datare vo LIESS ET eI et Qo IRI VE 6 14 Start Analog Input Object 0 0 0 0 02 eee eee 6 14 bos Data cor 205 303 toe Fo Lie he AE he th SUPR PRSE REM 6 14 Stop Analog Input Object 0 0 00 0 0 ee eee 6 15 Analog Input Examples 0 0 0 0 eens 6 16 Basic Steps for Acquiring Data 0 0050 6 16 Acquire Data with a Sound Card 0005 6 16 Acquire Data with a National Instruments Board 6 20 Evaluate Analog Input Object Status 6 24 Status Properties 0 0 0 cee eee 6 24 Display Summary 0 0 0 0 ec eee eee 6 25 Doing More with Analog Input 7 Configure and Sample Input Channels 7 2 Properties Associated with Configuring and Sampling Input Channels ues uut tardes toca tech dh ue us a age ees Sus ded 7 2 Configure Input Channel 0000 0 7 2 Sampling Rat s feed CAL seid Rs 7 9 Channel Skew llle 7 6 Manage Acquired Data 0 0 00 cece eee 7 9 Analog Input Data Management Properties 7 9 Preview Data asco dt eom Ug wc aaa MASS ate 7 9 Rules for Using peekdata llle 7 10 Poll the Data Block 0 0 0 0 eee ee 7 11 Extract Data from the Engine 00 00005 7 12 Preview and Extract Data 00 00
54. add a line from port 0 line 2 on Dev1 S daq createSession ni addDigitalChannel s Devi PortO Line2 InputOnly Add an analog input channel to your session addAnalogInputChannel s Dev1 0 Voltage ans Data acquisition session using National Instruments hardware Will run for 1 second 1000 scans at 1000 scans second Number of channels 2 index Type Device Channel MeasurementType Range Name 1 dio Devi portO line2 InputOnly n a 2 ai Dev1 aid Voltage Diff 10 to 10 Volts 18 9 18 session Bosed Digital Operations Plot the acquired digital data dataIn startForeground s plot dataIn 1 Related Examples Acquire Clocked Digital Data with Imported Clock on page 18 7 Acquire Digital Data Using Counter Channels on page 18 11 18 10 Acquire Digital Data Using Counter Channels Acquire Digital Data Using Counter Channels This example shows how to acquire clocked digital data using a counter output channel that generates pulses as an external clock The counter provides the clock in this acquisition DAQ Session Counter Pulse External digital Generation circuit Digital subsystem Key Intemal connection External wiring In this example we will generate a clock 1n one session using a counter output channel and export the clock to another session that acquires clocked digital data Note Importing an e
55. 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 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 addchannel provided channel 1 is added first addchannel ai 1 addchannel ai 2 6 7 6 Getting Started with Analog Input Alternatively you can use one call to addchannel provided channel 1 is specified as the first element of the hardware ID vector chan 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 chan 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 Configure Analog Input Properties Configure Analog Input Properties In this section Analog Input Basic Properties on page 6 9 Sampling Rate
56. and terminal pairs to which the external source is connected Two circumstances of externally clocked and triggered synchronization are An external hardware event that controls the operation of one or more devices in a session object For example opening and closing a switch starts a background acquisition on a session An external hardware event synchronizes multiple devices in a session For example opening and closing of a switch starts a background operation across multiple devices or CompactDAQ chassis in a session 21 3 2 Triggers and Clocks 21 4 Acquire Voltage Data Using a Digital Trigger This example shows how to use a falling edge digital trigger which occurs when a switch closes on an external source The trigger is connected to terminal PFIO on device Dev1 and starts acquiring sensor voltage data Create a data acquisition session and add channels S daq createSession ni Add one voltage input channel from NI USB 6211 with device ID Dev1 addAnalogInputChannel s Devi 0 Voltage Connect the switch to terminal PFIO on NI USB 6211 The trigger comes from the switch which is an external source addTriggerConnection s External Devi PFIO StartTrigger ans Start Trigger is provided externally and will be received by Dev i at terminal PFIO TriggerType Digital TriggerCondition RisingEdge Source External Destination Dev1 PFIO Type StartTrigger Set Tr
57. 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 Data Acquisition Toolbox software 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 Output Data with Sound Card Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB Getting Started with Analog Output In this example sine wave data is generated in the MATLAB workspace 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 You can run this example by typing daqdoc6 1 at the MATLAB Command Window 1 Create a device object Create the analog output object AO for a sound card The installed adaptors and hardware IDs are
58. 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 Record and Retrieve Event Information on page 7 44 for more information about returning absolute time information with the EventLog property Configure Analog Input Triggers Configure Analog Input Triggers In this section Analog Input Trigger Properties on page 7 19 Define Trigger Types and Conditions on page 7 20 Execute the Trigger on page 7 25 Trigger Delays on page 7 25 Repeat Triggers on page 7 28 How Many Triggers Occurred on page 7 33 When Did the Trigger Occur on page 7 34 Device Specific Hardware Triggers on page 7 35 Analog Input Trigger Properties 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 in the specified target Logging Off Logging On Xy s Tm Trigger occurs Log data to engine and disk file When defining a trigger you must specify the trigger type Additionally you might need to spe
59. ao addchannel ao 1 2 Configure property values Configure the sampling rate to 44 1 kHz for each channel ao SampleRate 44100 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 two digital I O ports you can run the following example which writes and reads digital values Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB You should modify this example to suit your specific application needs Adjust the example if the ports on your device do not support the input output directions specified here Accessing Your Hardware Create a device object Create the digital I O object dio for a National Instruments USB 6212 board with hardware ID Dev1 dio digitalio nidaq Devi Add output lines Add four lines from port 0 to dio and configure them for output
60. 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 Amplitude 1 13 T introduction to Data Acquisition 1 14 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 for more information about hardware sensitivity 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 on
61. 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 1 1 0 1 2 2 2 2 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 1s 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 Devi addline dio 0 7 0ut 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 Write and Read Digital I O Line Values putvalue dio Line 1 8 data 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 the preceding commands write to all eight lines contained by dio an eight element binar
62. cece ee eens A 9 What Is a Reserved Hardware Error A 11 What Are Devices with an Asterisk A 11 Network Devices Appears with an Asterisk A 12 ADC Overrun Error with External Clock A 12 Cannot Add Clock Connection to PXI Devices A 13 Cannot Complete Long Foreground Acquisition A 13 Cannot Use PXI 4461 and 4462 Together A 13 Counters Restart When You Call Prepare A 13 Cannot Get Correct Scan Rate with Digilent Devices A 13 Cannot Simultaneously Acquire and Generate with myDAQ Devices 2 3 joke GB Adem anedens de be Rd ed aed ab ones A 13 Counter Single Scan Returns NaN A 14 External Clock Will Not Trigger Scan A 14 Why Does My S PDIF Device Timeout A 14 Audio Output Channels Display Incorrect ScansOutputByHardware Value 5 A 14 Simultaneous Analog Input and Output Not Synchronized Correctly sne eb ped escena rU D ae UE E cens A 14 MOTU Device Not Working Correctly A 15 Legacy Interface Using All Devices A 16 Installed Adaptors 0 0 0 0 0c cece ene A 16 Advantech Hardware 0 0 eee tees A 16 Measurement Computing Hardware A 17 Sound Cards 22 dud ivt eue ed ein ld Dos Marner dp A 19 Other Manufacturers llle eee ees A 25 Contacting MathWorks 00 00 cece A 2
63. 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 file to execute when a trigger run time error or stop event occurs AI TriggerRepeat 3 time AI SamplesPerTrig AI SampleRate AI TriggerRepeat 1 Al TriggerFcn daqcallback Al RuntimeErrorFcn daqcallback Al StopFcn daqcallback 4 Acquire data Start AI and wait for it to stop running The wait function blocks the MATLAB Command Window and waits for AI to stop running start AT wait 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 Pass 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 Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB You can run this example by typing daqdoc5 7 at the MATLAB Command Window 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 Dev
64. create a session use this workflow to set up your counter and timer channels and acquire and generate multichannel audio addAudioInputChannel addAudioOutputChannel e output data Yes No See Also Functions addAudioInputChannel addAudioOutputChannel daq createSession daq getDevices queueOutputData startBackground startForeground Periodic Waveform Generation Workflow Periodic Waveform Generation Workflow Once you create a session use this workflow to create waveform generation channels and acquire waveforms generated on a Digilent Analog Discovery device function generation channels createSession addr r r Yes addanalogInputChannel gt Se Session Rate e tion General a unctionGeneratorChannel No Yes No x See Also Functions addAnalogInputChannel addFunctionGeneratorChannel daq createSession daq getDevices StartForeground Properties DurationInSeconds Rate 5 11 D Session Based Interface Workflows More About 2 Waveform Types on page 20 6 Getting Started with Analog Input Analog input AT 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 Data Acquisition Toolbox pr
65. 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 11 11 11 Saving and Loading 11 12 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 fileO00 daq info daginfo ObjInfo 1x1 struct HwInfo 1x1 struct To return the event log information eventinfo daqginfo ObjInfo 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 Oscilloscope Overview on page 12 2 Displaying Channels on page 12 5 Channel Data and Properties on page 12 13 Triggering the Oscilloscope on page 12 16 Making Measurements on page 12 19 Exporting Data on page 12 25 Saving and Loading the Oscilloscope Configuration on page 12 27 This examples in this chapter use Measurement Computing Demo Board which is installed with InstaCal or the Universal Library driver The Demo Board is a
66. devices specify the device to use stereo pairs In your MOTU Audio Console check Use Stereo Pairs for Windows Audio check box Specify desired sample rate in the Sample Rate field A 15 A Legacy Interface Using All Devices Legacy Interface Using All Devices A 16 In this section Installed Adaptors on page A 16 Advantech Hardware on page A 16 Measurement Computing Hardware on page A 17 Sound Cards on page A 19 Other Manufacturers on page A 25 Installed Adaptors Use daqhwinfo to discover installed National Instruments adaptors If the daqhwinfo nidaq command returns a warning you have devices that require you to use the Session Based Interface Warning Devices were detected that require the DAQ Session Based Interface For more information see documentation on the session based interface ans AdaptorDl1lName 1x103 char AdaptorDllVersion 3 0 R2011b Prerelease AdaptorName nidaq BoardNames 1x14 cell InstalledBoardIds 1x14 cell ObjectConstructorName 14x3 cell Advantech Hardware Driver Version on page A 17 Hardware Performance on page A 17 Note You can use Advantech hardware only with the legacy interface Legacy Interface Using All Devices Driver Version Data Acquisition Toolbox software is compatible only with specific versions of Advantech drivers and is not guaranteed to work with any other versions For a
67. does not match the minimum requirements specified on the product page on MathWorks website update your drivers If your driver is incompatible with Data Acquisition Toolbox verify that your hardware is functioning properly before updating drivers If your hardware is not functioning properly you are using unsupported drivers Visit the National Instruments website at http www ni com for the latest NI DAQ drivers To find driver version in the National Instruments Measurement amp Automation Explorer 1 Click Start Programs National Instruments Measurement amp Automation Explorer 2 Select Help gt System Information Why Doesn t My Hardware Work Use the Test Panel to troubleshoot your National Instruments hardware The Test Panel allows you to test each subsystem supported by your device and 1s installed as part of the NI DAQmx driver software Right click the device in the Measurement amp Automation Explorer and choose Test Panel For example to verify that the analog input subsystem on your PCIe 6363 device is operating connect a known signal similar to the signal produced by a function generator to one or more channels using a screw terminal panel If the Test Panel does not provide you with the expected results for the subsystem and you are sure that your test setup is configured correctly then the hardware is not performing correctly For your National Instruments hardware support visit their web
68. eee eee 7 14 Return Time Information 0 0 0 0 c eens 7 16 ix x Contents Configure Analog Input Triggers Analog Input Trigger Properties Define Trigger Types and Conditio Execute the Trigger Trigger Delays Repeat Triggers DS 6999 ek edes How Many Triggers Occurred 0 00 cee eeee When Did the Trigger Occur Device Specific Hardware Triggers Events and Callbacks 0 000 000 0c cc cece ee Events and Callbacks Basics Event Types 00005 Record and Retrieve Event Information Create and Execute Callback Functions Use Callback Properties and Functions Scaling Data Linearly Analog Input Engineering Units Properties Perform Linear Conversion Linear Conversion with Asymmetr 16 Data che he es SEES 7 19 7 19 7 20 7 25 7 25 7 28 7 33 7 34 7 35 7 41 7 41 7 41 7 44 7 47 7 49 7 52 7 52 7 53 7 55 Analog Output 8 Getting Started with Analog Output Create an Analog Output Object Add Channels to an Analog Output Object Analog Output Properties Output Dabaccui asso mpra Cte aste E hat SER Analog Output Examples Evaluate the Analog Output Object Status Manage Output Data Analog Output Subsystem Data Queus ied eene pe Pari
69. elements you use to access your hardware device 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 Configure properties 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 Queue data analog output only Before you can output analog data you must queue it in the engine with the putdata function Start acquisition or output of data To acquire or output data you must execute the device object with the start function Acquisition and output occurs in the background while MATLAB continues executing You can execute other MATLAB commands while the acquisition is occurring and then wait for the acquisition or output to complete Wait for the acquisition or output to complete You can continue working in the MATLAB workspace while the toolbox is acquiring or outputting data For more information see Analog Input and Outp
70. enable the CD or microphone for recording when the Select check box is selected for the CD or Microphone controls respectively Recording Control cd x Options Help Microphone CD Audio Line In Balance Balance Balance e A gt 4 lt gt 4a 4 Volume Volume Volume M Select Select Select Emu OKx Audio B800 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 microphone 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 A 22 Legacy Interface Using All Devices Unpowered microphone jack pum Powered microphone jack You can find out which sound card brand you have installed by clicking the Devices tab on the Sounds and Audio Devices Properties dialog box Refer to Sound Cards on page A 19 for a picture of this dialog box Test with a Microphone To test your sound card with a microphone follow these steps 1 N 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
71. eo t eet t Queue Data with putdata Configure Analog Output Triggers Analog Output Trigger Properties 8 2 8 2 8 3 8 4 8 7 8 11 8 15 8 15 8 15 8 17 8 19 8 19 Define Trigger Types llle 8 20 Execute Trigsers e a 44a e n RUE 8 21 How Many Triggers Occurred llle 8 21 When Did the Trigger Occur 0 0 0 0 00 eee 8 22 Device Specific Hardware Triggers 2005 8 23 Events and Callbacks 0 0 00 0 0c ccc ees 8 25 Events and Callbacks Basics 0 00000 ce eee 8 25 Event lypes 209249099 ee SR IR ERE AS RD ESQ 8 25 Record and Retrieve Event Information 8 27 Use Callback Properties and Callback Functions 8 30 Scale Data Linearly l l 8 33 Engineerimg Units osrand 454a ye Te Re oe 8 33 Perform a Linear Conversion 00000005 8 34 Start Multiple Device Objects 8 36 Advanced Configurations Using Analog Input and Analog Output 9 Start Analog Input and Output Simultaneously 9 2 Synchronize Analog Input and Output Using RTSI 9 4 Digital Input Output 10 Digital I O Subsystems 0 00 0 ees 10 2 Digital VO Objects epbesaumirerseermrd eeu we ge 10 3 Create a Digital I O Object 0 0 00 eee eee 10 3 Parallel Ports i se baat ak eee 2 Bolen Bra wie Wee 10 4 Add Lines to Digital I O Objects 10 6 Use the Addli
72. from an analog input subsystem to the engine memory or to a disk file 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 Imnediate which executes the trigger immediately after the start function is issued For a detailed 4 21 4 Data Acquisition Workflow 4 22 description of triggers refer to Configure Analog Input Triggers on page 7 19 or Configure Analog Output Triggers on page 8 19 Extract 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 logged 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 Window until all the requested data is returned to the workspace You can extract data any time after the trigger occurs Send 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 addcha
73. getdata function 87 200 samples remain in the engine 7 24 Configure Analog Input Triggers AIVoice SamplesAvailable ans 87200 Execute 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 after 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 t
74. in the engine Instead you either write values directly to or read values directly from the hardware lines You can read values from one or more lines with the getvalue function getvalue requires the DIO object as an input argument You can optionally specify an output argument which represents the returned values as a binary vector Binary vectors are described in Write Digital Values on page 10 14 For example suppose you create the digital I O object dio and add eight input lines to it from port 0 dio digitalio nidaq Devi 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 Rules for Reading Digital Values Reading values from digital I O lines follows these rules Write and Read Digital O Line Values 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 Youcan always read from a line configured for output For National Instruments hardware using
75. in the variable P The amount of data to display is given by preview duration 10 Ten second acquisition AI SampleRate 8000 ActualRate AI SampleRate AI SamplesPerTrigger duration ActualRate preview duration ActualRate 100 subplot 211 P plot zeros preview 1 grid on title Preview Data xlabel Samples ylabel Signal Level Volts 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 preview end while AI SamplesAcquired lt duration ActualRate data peekdata AI preview P ydata data drawnow end Extract all the acquired data from the engine and plot the data wait AI durationt 1 data getdata AI 7 15 7 Doing More with Analog Input 7 16 subplot 212 plot data grid on title All Acquired Data xlabel Samples ylabel Signal level 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 The data is shown below Preview Data Signal Level Volts 0 100 200 300 40 500 e00 700 s00 Samples All Acquired Data Signal level vols
76. in this case a sound card Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB Bring Analog Data into a Model Step 1 Open the Data Acquisition Toolbox Block Library To use the Analog Input block you must open the Data Acquisition Toolbox block library To open the library start the Simulink Library Browser and select Data Acquisition Toolbox software entry from the list displayed in the browser Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB To start the Simulink Library Browser enter simulink at the MATLAB Command window In the Simulink Library Browser the left pane lists the available block libraries To open the Data Acquisition Toolbox block library click its icon Step 2 Create a New Model To use a block you must add it to an existing model or create a new model Build Models to Acquire Data Create a new model by clicking the Create a new model button in the Simulink Library Browser Simulink Library Browser DEN 10 x File Edit View Help Enter search term 4 GV Library Data Acquisition Toolbox Search Results none Most Frequ ooroo DSP System Toolbox Data Acquisition Toolbox Analog Input Embedded Coder Fuzzy Logic Toolbo
77. is 2 5 then the scaled value is 2 5 20 2 or 25 in the appropriate units Perform 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 Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB 7 53 7 Doing More with Analog Input 7 54 A microphone is connected to a device which is undergoing a vibration test Your job is to measure the acceleration and the frequency components of the device while it is vibrating The microphone 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 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 Window 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 nidaq Devi 2 Add channels Add one hardware channel to AI chan addchannel AI 0 3 Configure property values Configure the sampling rate to
78. it from memory and from the MATLAB workspace delete AI clear AI Analyze Data Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB For this experiment analysis consists of finding the frequency of the input signal and plotting the results You can find the signal frequency with daqdocf ft f mag daqdocfft data Fs blocksize This function which is shown in Analyze Data on page 6 18 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 The results are given below plot f mag grid on ylabel Magnitude dB xlabel Frequency Hz title Frequency Output by Function Generator Analog Input Examples Frequency Outputby Function Generator Magnitude dB 8 e SU Te HON UNE ELIO 5000 3500 4500 2500 3000 4000 Frequency Hz o 500 1500 2000 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 6 23 6 Getting Started with Analog Input Evaluate Analog Input Object Status 6 24 In this section Status Properties on page 6 24 Display Summary on p
79. list of the Advantech driver versions that are compatible with Data Acquisition Toolbox software refer to the product page on MathWorks website at http www mathworks com products daq supportedio html and click the link for this vendor If you think your driver is incompatible with Data Acquisition Toolbox software verify that your hardware is functioning properly before updating drivers If your hardware is not functioning properly then you are probably using unsupported drivers For the latest drivers visit the Advantech website at http www advantech com With the Advantech Device Manager you can find out which version of Advantech drivers you are using You can access this program though the Windows desktop To see if a specific version of a driver is installed on your system select the type of device in the Supported Devices list and click About Hardware Performance To troubleshoot your Advantech hardware you use the Advantech Device Test dialog box This dialog box allows you to test each subsystem supported by your board and is installed as part of the Advantech Device Manager To access the Advantech Device Test dialog box from the Advantech Device Manager select the appropriate device in the Installed Devices list and click Test For example suppose you want to verify that the analog input subsystem on your PCI 1710 board is operating correctly To do this connect a known signal such as that produced by a functi
80. lot of overhead time spent saving setting up and restoring the register information Therefore depending on your specific Analog Input Subsystem 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 1t into in system memory as soon as possible 2 Assoon as the CPU is able which is usually very quickly it stops interacting with the data acquisition hardware 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 31 T introduction to Data Acquisition Making Quality Measurements 1 32 In this section What Do
81. 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 Data Acquisition Toolbox software 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 1s 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 You select certain property values For example if the samples to acquire per trigger are significantly less than the FIFO buffer of your hardware 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 i
82. object or a channel object at the MATLAB Command Window or by excluding the semicolon when Creating an AI object Adding channels 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 Display Summary from the context menu The displayed information reflects many of the basic setup properties described in Configure Analog Input Properties on page 6 9 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 Acquisition parameters Thesampling rate The number of samples to acquire per trigger The acquisition duration for each trigger The destination for logged data Trigger parameters The trigger type The number of triggers including the number of triggers already executed 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 6 25 6 Getting Started with Analog Input 6 26 Channel Summary Information The channel display summary includes property valu
83. of externally clocked synchronization include Synchronizing operations on all devices within a session by sharing the clock on a device within the session or an external clock Synchronizing operations on all devices within a session and some external devices by sharing an external clock Note Importing an external clock does not automatically set the rate of your session Manually set the session s rate to match the expected external clock frequency 21 5 2 Triggers and Clocks 21 6 Export Scan Clock to External System This example shows how to add a scan clock to a device and output the clock to a device outside your session which is connected to an oscilloscope The scan clock controls the operations on the external device Create a session and add one voltage input channel from NI USB 6211 with device ID Dev1 S daq createSession ni addAnalogInputChannel s Devi 0 Voltage Add an external clock to terminal PFI6 on Dev1 and connect it to an external destination addClockConnection s Dev1 PFI6 External ScanClock ans Scan Clock for Devi will available at terminal PFI6 for external use Source Dev1 PFI6 Destination External Type ScanClock Acquire data and store it in dataIn dataIn startForeground s Related Examples Multiple Device Synchronization on page 22 7 u Multiple Chassis Synchronization on page 22 11 More About Synchronizatio
84. 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 digital 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 1s shown below 1 QOOOOOOOoOoOoOoOoOQ 25 pin female parallel port OOOOOOOO00000 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 The toolbox groups the 17 nonground lines into three separate ports The port IDs and the associated pin numbers are given below 10 9 10 Digital Input Output 10 10 Table 10 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 10 13 and 15 Five input lines used for status 2 1 14 16 and 17 Four I O lines used for control 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 E
85. properties apply to all Getting Started with Analog Output 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 8 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 Set 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 Dev addchannel ao 0 1 ao SampleRate 100000 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 Ifthe rate is within the range of valid values then the engine automatically select
86. queued data is output Timeout Specify an additional waiting time to queue data Data Queuing 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 8 15 8 Analog Output 8 16 A data source consisting of m samples and n channels is illustrated below dmi dine din don dan Data source Each column represents a separate output channel dmn Rules for Using putdata Using putdata to queue data in the engine follows these rules You must queue data in the engine before starting the analog output object Ifthe value of the RepeatOutput property is greater than 0 then all queued data 1s automatically requeued until the RepeatOutput value is reached You must configure RepeatOutput before start is issued While the analog output object is running you can continue to queue data unless RepeatOutput is greater than 0 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 Manage Output Data Rule
87. 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 precision one part in 2 mber of bits The precision in volts is given by voltage range gnumber of bits precision For example if you are using a 12 bit A D converter configured for a 10 volt range then 10 volts precision 9i2 Making Quality Measurements 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 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 Relationship Between Input Range Gain and Precision Input Range Gain Actual Input Range Precision 1
88. read and analyzed to extract meaningful information T introduction to Data Acquisition 1 10 For example sound level data is acquired from a microphone amplified digitized by a sound card and stored in MATLAB workspace for subsequent analysis of frequency content Data from a computer is converted into an analog signal and output to an actuator For example a vector of data in MATLAB workspace 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 which is typically a USB cable 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 Analog input Analog output 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 Data Acquisition System 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 subsy
89. 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 1s the relative time associated with the retrieved data Time 1s 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 file is the name of the log file 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 1s separated by a NaN You select the amount of data returned and the format of that data with the properties given below Table 11 1 daqread Properties Property Name Description Samples Specify the sample range 11 7 11 Saving and Loading 11 8 Property Name Description 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 If none of these three properties is specified then all the data is retur
90. session See Synchronization on page 22 2 for more information Session Based Interface and Data Acquisition Toolbox Data Acquisition Toolbox and the MATLAB technical computing environment use the session based interface to communicate with National Instruments devices including a CompactDAQ chassis You can operate in the foreground where the operation blocks MATLAB until complete or in the background where MATLAB continues to run additional MATLAB commands in parallel with the hardware operation See Session Creation Workflow on page 5 2 for more information You can create a session with both analog input and analog output channels and configure acquisition and generation simultaneously See Acquire Data and Generate Signals Simultaneously on page 16 25 for more information Digital Input and Output Digital Input and Output Digital subsystems transfer digital or logical values in bits via digital lines You can perform clocked and non clocked digital operations using the session based interface in the Data Acquisition Toolbox For more information see Digital Subsystem Channels on page 18 2 14 5 14 Using the Session Based Interface Discover Hardware Devices This example shows how to discover devices on your system Step 1 Discover hardware devices d daq getDevices de Data acquisition devices index Vendor Device ID Description 1 ni cDAG1Mod1 National Instruments NI 9205 2 ni cDAQ
91. simultaneous signals However devices are automatically and perfectly synchronized in the session if they are Subsystems on a single device in the session This synchronizes your analog input analog output and counter input channels Note Counter output channels run independently and are unaffected by synchronization connections Modules on a single CompactDAQ chassis in the session PXI modules synchronized with a reference clock on a PXI chassis For perfect synchronization you must share a trigger as well See Acquire Synchronized Data Using PXI Devices on page 22 9 for more information Multiple Device Synchronization Multiple Device Synchronization You can synchronize multiple devices in a session using a shared clock and trigger You can synchronize devices using either PFI or RTSI lines Requirement You must register your RTSI cable using the National Instruments Measurement amp Automation Explorer Acquire Synchronized Data Using USB Devices This example shows how to acquire synchronized voltage data from multiple devices using a shared trigger and a shared clock Analog input channels on all three devices are connected to the same function generator Create a data acquisition session and add channels and add one voltage input channel each from NIUSB 6211 with device ID Dev1 NI USB 6218 with device ID Dev2 NI USB 6255 with device ID Dev3 S daq createSession addAnalogInput
92. start ai wait ai duration 1 data timestamps getdata ai Plot the data plot timestamps data Session Based Interface You can specify an external event to trigger data acquisition using the session based interface 1 Create a session and add two analog input channels S daq createSession ni ch addAnalogInputChannel s Devi 0 1 Voltage Configure the terminal and range of the channels in the session ch 1 TerminalConfig SingleEnded ch 1 Range 10 0 10 0 ch 2 TerminalConfig SingleEnded 23 5 23 Transition Your Code to Session Based Interface 23 6 ch 2 Range 10 0 10 0 3 Create an external trigger connection and set the trigger to run one time addTriggerConnection s External Dev1 PFIO StartTrigger s Connections 1 TriggerCondition RisingEdge s TriggersPerRun 1 4 Set the rate and the duration of the acquisition s Rate 50000 s DurationInSeconds 0 01 5 Acquire data in the foreground and plot the data data timestamps startForeground s plot timestamps data Log Data Legacy Interface You can log the data to disk and use daqread to read the data back 1 Create the analog input object and add two channels ai analoginput winsound ch addchannel ai 0 1 Define a 2 second acquisition for each trigger set the trigger to repeat three times and log information to the file file00 daq Il duration 2 a
93. system are amplified by a Texas Instruments ULN2003AIN High Voltage High Current Darlington Transistor Array as shown in this schematic 18 16 Control Stepper Motor using Digital Outputs Unipolar 6 wire Stepper Motor PortO LineO PortO Line1 PortO Line2 PortO Line3 ULN 2003A 5V Add Digital Output Only Channels Create a session and add 4 digital channels on port 0 lines 0 3 Set the measurement type to OutputOnly These are connected to the four control lines for the stepper motor S daq createSession ni addDigitalChannel s Dev2 portO line0O 3 OutputOnly Warning A channel that does not support clocked sampling was added to the session Clocked operations using startForeground and startBackground will be disabled Only on demand operations using inputSingleScan and outputSingleScan can be done ans Data acquisition session using National Instruments hardware Clocked operations using startForeground and startBackground are disabled Only on demand operations using inputSingleScan and outputSingleScan can be done Number of channels 4 index Type Device Channel MeasurementType Range Name 18 17 18 session Based Digital Operations 18 18 1 dio Dev2 portO lineO OutputOnly n a 2 dio Dev2 portO line1 OutputOnly n a 3 dio Dev2 portO line2 OutputOnly n a 4 dio Dev2 portO line3 OutputOnly n a Define Motor Steps Refer to the Portescap motor wiring diagram describing the sequence of
94. the MATLAB Command Window Trigger 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 Retrieve Event Information Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB Suppose you want to examine the events logged for the example given by Voice Activation Using a Software Trigger on page 7 23 You can do this by accessing the EventLog property events AIVoice EventLog events 3x1 struct array with fields Events and Callbacks 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 O Channel 1 Trigger 1 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 sh
95. the Traditional NI DAQ interface lines configured for output return a value of 1 by default Note The Traditional NI DAQ adaptor will be deprecated in a future version of the toolbox If you create a Data Acquisition Toolbox M object for Traditional NI DAQ adaptor beginning in R2008b you will receive a warning stating that this adaptor will be removed in a future release See the supported hardware page at www mathworks com products daq supportedio html for more information getvalue always returns a binary vector binvec To convert the binvec to a decimal value use the binvec2dec function Write and Read Digital Values 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 Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB You can run this example by typing daqdoc7 1 at the MATLAB Command Window 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 Devi 2 Add lines Add eight output lines from port 0 line configurable addline dio 0 7 0ut 3 Read and write values Write a value of 13 to the first four lines as a decimal number and a
96. the block s icon in the Simulink editor This opens the Source Block Parameters dialog box for the Analog Input block shown in the following figure Use the various fields to determine the current values of the Analog Input block parameters or to change the values 13 9 13 Using the Data Acquisition Blocks in Simulink i Source Block Parameters Analog Input X m Analog Input Acquire block of data from multiple analog channels of a data acquisition device every simulation time step r Parameters Acquisition Mode G Asynchronous Initiates the acquisition when simulation starts The simulation runs while data is acquired into a FIFO buffer C Synchronous Initiates the acquisition at each time step The simulation will not continue until all data is acquired Device winsoundO Aux Realtek High Definition au gt Hardware sample rate samples second sao Actual rate will be 8000 samples per second Block size 5 Inputtype AC Coupled s Channels Select All Unselect an __ Hardware Channel Name Input Range v 1V to 1V iz Outputs EE for al hardware channeis M pie based N a0 X X 15 cancel Heip Apply In this example keep the default settings for everything except Block size Change the block size setting to 5 which means five samples will be acquired from each channel at 13 10 Build Models to Acquire Data every
97. the engine with one call to getdata returndata ActualRate duration AlVoice TriggerRepeat 1 start AIVoice wait AlVoice duration 1i 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 The multiple trigger data is shown below Configure Analog Input Triggers Voice Actvaton tor Both Triggers Signal Level Vadis 0 02 0A 05 os 1 12 1 4 Time sec You can find the 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 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 7 33 7 Doing More with Analog Input 7 34 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 ai TriggerRepeat 4 start ai
98. the temperature varies between the limits depends on several factors including your driving habits the weather and the condition of the cooling Data Acquisition System 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 these unlimited possibilities are mapped to a finite set of values by your data acquisition hardware 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 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 sen
99. there are significant differences in these ranges or the data is not symmetric then using different values for these properties might be appropriate as illustrated in the following scenario Suppose you have a speed sensor that generates 5 volts to 7 volts according to the detected speed so you set SensorRange to 5 7 When the sensor detects a speed of 0 m s it generates a 5 volt signal when it senses 20 m s it generates a 7 volt signal so you set UnitsRange to O 20 t Dat Acquistion Data Acquisifon Toolbox Speed Sensor SensorRange Devke Tan 10 V 10V Converts voltage data into speed Moiteun InputRange 5V107 V 01020 m s For example when the sensor transmits 6 volts Data Acquisition Toolbox software converts this value according to the formula 7 55 7 Doing More with Analog Input scaled value Sensor output Offset x UnitsRange SensorRange scaled value 6 V 5 V x 20 0 7 5 scaled value 1 x 20 2 scaled value 10 m s For a sensor output value of 6 5 V scaled value 6 5 5 x 20 2 15 m s and so on as shown in the following graph Linear Data Conversion 20 Scaled Value m s 5 5 5 6 6 5 7 Sensor Output V 7 56 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 a
100. to acquire and generate data on a 64 bit MATLAB You can run this example by typing daqdoc7 2 at the MATLAB Command Window 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 Dev 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 dio TimerFcn daqcallback 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 10 21 10 Digital Input Output Evaluate Digital I O Object Status 10 22 In this section Running Property on page 10 22 Display Summary on page 10 22 Running Property You can evaluate the status of a digital I O DIO object by returning the value of the Running property this is useful only if timer events are generated Display Summary You can invoke the display summary by typing a DIO object or a line object at the MATLAB Command Window or by excluding the sem
101. to add a channel that acquires edge count from a device You can acquire a single input data or an array by acquiring in the foreground For details see About the Session Based Interface on page 14 2 for more information Acquire a Single EdgeCount This example shows how to acquire a single falling edge data from an NI USB 9402 with device ID cDAQ1Mod5 Step 1 Create a session object and save it to the variable s S daq createSession ni Step 2 Add a counter channel with an EdgeCount measurement type ch addCounterInputChannel s cDAQ1Mod5 ctrO EdgeCount ans Data acquisition session using National Instruments hardware Will run for 1 second 1000 scans at 1000 scans second Operation starts immediately Number of channels 1 1 ci cDAQ1Mod5 ctro EdgeCount n a Step 3 Change the ActiveEdge property to Falling and view the channel properties to see the change 17 3 17 Session Based Counter Input and Output 17 4 ch ActiveEdge Falling ans Data acquisition counter input edge count channel ctrO on device cDAQ1Mod5 ActiveEdge Falling CountDirection Increment InitialCount O Terminal PFIO IsCounterRunning false Name empty ID etro Device 1x1 daq ni CompactDAQModule MeasurementType EdgeCount Step 4 Acquire a single scan inputSingleScan s ans 133 Step 5 Reset counters from the initial count and acquire the count again resetCounters s inpu
102. 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 Glossary output range posttrigger data precision pretrigger data properties quantization queuing data running sample rate sampling scan cases the onboard clock controls the sampling rate of the board The span of output values for which a D A conversion is valid Data that 1s 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 engine for eventual output to an analog output subsystem A state of Data Acquisition Toolbox software 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 con
103. to your system d daq getDevices 2 Create a session for National Instruments devices S daq createSession ni 3 Setthe session s sample rate to 8000 s Rate 8000 4 Add an analog input channel for the device with ID Dev1 with Voltage measurement type and start the acquisition addAnalogInputChannel s Devi 1 Voltage startForeground s Use Triggers Acquire analog data using hardware triggers Legacy Interface Analog operations are configured to trigger immediately by default You must specify hwDigital trigger type Create an analog input object and add two channels 1 Create an analog input object and add two channels ai analoginput nidaq Dev chan addchannel ai 0 1 Transition Your Code to Session Based Interface Specify the ranges of the channel to scale the data uniformly Configure the input type to be SingleEnded terminal chan InputRange 10 10 chan UnitsRange 10 10 chan SensorRange 10 10 chan InputType SingleEnded Specify the trigger type source and condition Set TriggerRepeat to 0 ai TriggerType HwDigital ai HwDigitalTriggerSource PFIO ai TriggerCondition PositiveEdge ai TriggerRepeat 0 Specify rate and duration actualRate setverify ai SampleRate 50000 duration 0 01 ai SamplesPerTrigger duration actualRate Start the channel wait until the channel receives the specified amount of data and get the data
104. 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 showdaqevents function For example suppose you create the analog output object ao for a sound card and add 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 8 21 8 Analog Output 8 22 data sin linspace 0 1 8000 putdata ao data start ao 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 0 3 Stop 10 43 26 8000 For more information about recording and retrieving event information refer to Record and Retrieve Event Information on page 8 27 When Did the Trigger Occur Yo
105. 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 the MATLAB workspace with the daqfind function Session Based Interface Workflows Session Creation Workflow on page 5 2 Analog Input and Output Workflow on page 5 5 Digital Input and Output Workflow on page 5 7 Counter and Timer Input and Output Workflow on page 5 9 Multichannel Audio Input and Output Workflow on page 5 10 Periodic Waveform Generation Workflow on page 5 11 D Session Based Interface Workflows Session Creation Workflow This workflow helps you create a data acquisition or generation session Discover available devices daq getDevices Get vendor information daq getVendors C eate session daq createSession Once you create a session you can use this workflow to acquire or generate data Session Creation Workflow Discove 4 devices daq getbevices addAnalogInputChannel addanalogoutpu addaudiornput addaudiooutputchai addCounterInputChannel ad dCounterOutputChannel 1 put data queueOutputData startBackground Run other MATLAB See Also Functions oper startForeground ad
106. when the digital signal 1s high TrigLow The trigger occurs when the digital signal 1s low TrigPosEdge The trigger occurs when the positive rising edge of the digital signal 1s detected TrigNegEdge The trigger occurs when the negative falling edge of the digital signal is detected 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 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
107. 0 Voltage Synchronize the two channels using the AutoSyncDSA property s AutoSyncDSA true Acquire data in the foreground and plot it data time startForeground s 22 17 22 session Based Synchronization 22 18 plot time data Handle Filter Delays with DSA Devices DSA devices have a built in digital filter You must account for filter delays when synchronizing between heterogeneous devices Refer to your device manuals for filter delay information For more information see the NI knowledge base article Why Is My Data Delayed When Using DSA Devices Document ID 2UI8PGX4 Account for Filter Delays This example shows how to account for filter delays when you use the same sine wave to acquire from two different channels from 2 different PXI devices Perfectly synchronized channels will show zero phase lag between the two acquired signals Create a session and add two analog input channels with Voltage measurement type from National Instruments PXI 4462 and NI PXI 4472 S daq createSession ni chi addAnalogInputChannel s PXIiSlot2 0 Voltage ch2 addAnalogInputChannel s PXI1S10t3 0 Voltage Acquire unsynchronized data and plot it data time startForeground s plot time data Use AutoSyncDSA to automatically configure the triggers clocks and sync pulses of the channels to synchronize the devices s AutoSyncDSA true Acquire synchronized data data time startF
108. 2 17 Handle Filter Delays with DSA Devices 22 18 Transition Your Code to Session Based Interface 23 Transition Your Code to Session Based Interface 23 2 Transition Common Workflow Commands 23 2 Acquire Analog Data 0 0 0 0 ccc ee eee 23 3 Wise Tri 8 Ors a eb od Geir wee hn ERE ERU RUE es 23 4 Tos Data e zoe t ead EC Sy edu a RR ae 23 6 Set Range of Analog Input Subsystem 23 7 Fire an Event When Number of Scans Exceed Specified Mri rM c 23 8 Use Timeout to Block MATLAB While an Operation Completes as eost e t a De ye bete psi 23 9 Count Pulses 5a ume cecus eres eu E V ES 23 10 Troubleshooting Your Hardware A Supported Hardware l l A 2 Hardware and Device Drivers llllllsn A 3 Registering the Hardware Driver Adaptor A 3 Device Driver Registration 0 000 c eee eee A 4 xviii Contents Hardware Diagnostics llle A 4 Session Based Interface Using National Instruments Devices x 2 534 oet oss Mo aa ny er e a ae ese ips Sa A 5 Session Based Interface and Legacy Interface A 5 Is My NI DAQ Driver Supported 00 005 A 6 Why Doesn t My Hardware Work 000005 A 7 Cannot Create Session 0 0c cee eens A 8 Why Was My Session was Deleted A 8 Cannot Find Hardware Vendor 000 eee A 8 Cannot Find Devices 0000
109. 2 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 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 Data Acquisition Toolbox software you do not have to specify the range and gain Instead you simply specify the actual input range desired 1 35 T introduction to Data Acquisition 1 36 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 amplifier 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 th
110. 2Mod1 National Instruments NI 9201 3 ni Dev1 National Instruments USB 6211 4 ni PXI1Slot2 National Instruments PXI 4461 Click the device ID for detailed device information Step 2 Get detailed device information d 3 ans ni National Instruments USB 6211 Device ID Devi Analog input subsystem supports 4 ranges supported Rates from 0 1 to 250000 0 scans sec 16 channels aiO aii5 Voltage measurement type Analog output subsystem supports 10 to 10 Volts range Rates from 0 1 to 250000 0 scans sec 2 channels ao0 ao1 Voltage measurement type Digital subsystem supports 8 channels portO lineO porti line3 InputOnly OutputOnly measurement types Counter input subsystem supports 14 6 Discover Hardware Devices Rates from 0 1 to 80000000 0 scans sec 2 channels ctrO ctr1 EdgeCount PulseWidth Frequency Position measurement types Counter output subsystem supports Rates from 0 1 to 80000000 0 scans sec 2 channels ctrO ctr1 PulseGeneration measurement type Properties Methods Events Detailed device information includes Subsystem type Rate Number of available channels Measurement type 14 7 14 Using the Session Based Interface Create a Session 14 8 This example shows how to create a session and add channels to the session and use the session to acquire and generate data You can also configure session and channel properties needed
111. 4 bit patterns Send this pattern sequentially to the motor to produce counterclockwise motion Each step turns the motor 18 degrees Each cycle of 4 steps turns the motor 72 degrees Repeat this sequence five times to rotate the motor 360 degrees step 1 0 1 0 step2 1 0 O 1 step3 0 1 0 1 step4 0 1 1 0 Rotate Motor Use outputSingleScan to output the sequence to turn the motor 72 degrees counterclockwise outputSingleScan outputSingleScan outputSingleScan outputSingleScan s step1 s step2 s step3 s step4 Repeat sequence 50 times to rotate the motor 10 times counterclockwise for motorstep 1 50 outputSingleScan s step1 outputSingleScan s step2 outputSingleScan s step3 outputSingleScan s step4 end To turn the motor 72 degrees clockwise reverse the order of the steps outputSingleScan outputSingleScan outputSingleScan outputSingleScan S Step4 s steps3 s step2 s step1 Control Stepper Motor using Digital Outputs Turn Off All Outputs After you use the motor turn off all the lines to allow the motor to rotate freely outputSingleScan s O 0 O 0 18 19 18 session Based Digital Operations Generate Non Clocked Digital Data 18 20 This example shows how to write data to two lines on an NI 625 Find devices connected to your system and find the ID for NI 6255 I d daq getDevices d Data acquisition dev
112. 6 xix XX Contents Hardware Limitations by Vendor National Instruments Hardware B 2 Digilent Analog Discovery Devices B 4 Measurement Computing Hardware B 5 Windows Sound Cards 0 eee eee B 6 Managing Your Memory Resources C What is Memory Allocation llle C 2 How Much Memory Do You Need C 4 Using Allocated Memory eeleeesns C 5 Glossary Introduction to Data Acquisition Data Acquisition Toolbox Product Description on page 1 2 Product Capabilities on page 1 3 Anatomy of a Data Acquisition Experiment on page 1 6 Data Acquisition System on page 1 8 Analog Input Subsystem on page 1 20 Making Quality Measurements on page 1 32 Getting Command Line Function Help on page 1 41 Selected Bibliography on page 1 42 1 Introduction to Data Acquisition Data Acquisition Toolbox Product Description Connect to data acquisition cards devices and modules Data Acquisition Toolbox provides functions for connecting MATLAB to data acquisition hardware The toolbox supports a variety of DAQ hardware including USB PCI PCI Express PXI and PXI Express devices from National Instruments Measurement Computing Advantech Data Translation and other vendors With the toolbox you can configure data acquisition hardware and read data into
113. All channels associated with this device were updated Change the acquisition rate to 10 scans per second s Rate 10 s Data acquisition session using National Instruments hardware Will run for 1 second 10 scans at 10 scans second Number of channels 1 index Type Device Channel MeasurementType Range Name 1 ai cDAQ1Mod7 aii Bridge Unknown 0 025 to 0 025 VoltsPerVolt Set BridgeMode to Full which uses all four resistors in the device to acquire the voltage values ch BridgeMode Full ch Data acquisition analog input channel aii on device cDAQ1Mod7 BridgeMode Full ExcitationSource Internal ExcitationVoltage 2 5 NominalBridgeResistance Unknown Range 0 063 to 0 063 VoltsPerVolt Name empty ID ait Device 1x1 daq ni CompactDAQModule MeasurementType Bridge ADCTimingMode HighSpeed Set the resistance of the bridge device to 350 ohms Acquire Analog Input Data ch NominalBridgeResistance 350 ch Data acquisition analog input channel aii on device cDAQ1Mod7 BridgeMode Full ExcitationSource Internal ExcitationVoltage 2 5 NominalBridgeResistance 350 Range 0 063 to 0 063 VoltsPerVolt Name empty ID ait Device 1x1 daq ni CompactDAQModule MeasurementType Bridge ADCTimingMode HighSpeed Save the acquired data to a variable and start the acquisition data startForeground s Plot the acquired data plot data Acquire Sound Pressure Data This example
114. Channel addAnalogInputChannel addAnalogInputChannel ni s Devi O Voltage s Dev2 O Voltage s Dev3 O Voltage Choose terminal PFI4 on Dev1 as the trigger source Connect the trigger source to terminal PFIO on Dev2 and PFIO on Dev3 which are the destination devices addTriggerConnection s Dev1 PFI4 Dev2 PFIO StartTrigger addTriggerConnection s Dev1 PFI4 Dev3 PFIO StartTrigger Chose terminal PFI5 on Dev1 as the clock source Connect it to PFI1 on Dev2 and PFI1 on Dev3 s addClockConnection Devi PFI5 Dev2 PFI1 ScanClock s addClockConnection Devi PFI5 Dev3 PFI1 ScanClock ans Start Trigger is provided by Devi at PFI4 and will be received by 22 7 22 Session Based Synchronization Dev2 at terminal PFIO Dev3 at terminal PFIO Scan Clock is provided by Devi at PFI5 and will be received by Dev2 at terminal PFI1 Dev3 at terminal PFI1 index Type Source Destination 1 StartTrigger Dev1 PFI4 Dev2 PFIO 2 StartTrigger Dev1 PFI4 Dev3 PFIO 3 ScanClock Dev1 PFI5 Dev2 PFI1 4 ScanClock Dev1 PFI5 Dev3 PFI1 Acquire data and store it in dataIn dataIn startForeground s Plot the data plot dataIn N6H8 s 88ed84 8 08 e0 22 8 Multiple Device Synchronization All channels are connected to the same function generator and therefore display overlapping signals showing perfect synchronizatio
115. CompactDAQ chassis or counter timers see Counter and Timer Input and Output Data Acquisition Engine The data acquisition engine or just engine is a MEX file shared library that is executable within the MATLAB software that Stores the device objects and associated property values that control your data acquisition application Toolbox Components Controls the synchronization of events 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 the MATLAB software are asynchronous The relationship between acquiring data outputting data and data flow is described next 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 memory until you explicitly extract it using the getdata function If you do not extract this data and the amount of data stored in memory reaches the limit for the data acquisition object see daqmem obj a DataMissed event occurs At this point the acquisition stops The rate at which the acquisition stops 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 flow of acquired data consists of these two independent steps 1 Data acquired from the hardware
116. Connection to PXI Devices on page A 13 Cannot Complete Long Foreground Acquisition on page A 13 Cannot Use PXI 4461 and 4462 Together on page A 13 Counters Restart When You Call Prepare on page A 13 Cannot Get Correct Scan Rate with Digilent Devices on page A 13 Cannot Simultaneously Acquire and Generate with myDAQ Devices on page A 13 Counter Single Scan Returns NaN on page A 14 External Clock Will Not Trigger Scan on page A 14 Why Does My S PDIF Device Timeout on page A 14 Audio Output Channels Display Incorrect ScansOutputByHardware Value on page A 14 Simultaneous Analog Input and Output Not Synchronized Correctly on page A 14 MOTU Device Not Working Correctly on page A 15 Session Based Interface and Legacy Interface You can use National Instruments devices with both the session based interface and the legacy interface To see which interface you need to use refer to National Instruments A 5 Session Based Interface Using National Instruments Devices Usage Based on Functionality For more information on the session based information see Session Based Interface daqhwinfo nidaq AdaptorDl1lName 1x63 char AdaptorDllVersion 3 0 R2011b AdaptorName nidaq BoardNames PCI 4472 InstalledBoardIds Dev4 1 ObjectConstructorName 2x3 cell If the daqhwinfo nidaq command returns a warning about session based interface you have devi
117. Count Pulses on page 23 10 Transition Common Workflow Commands This table lists the legacy commands for common workflows and their corresponding session based commands To do this Find supported daqhwinfo hardware available to your system Session Based Command Legacy Command daq getDevices Registered DAQ daqregister You do not need to register an adaptor if you adaptor are using session based interface Reset MATLAB to initial daqreset daq reset state Discover newly Shut down MATLAB and connected hardware restart daq reset s daq createSession ni addAnalogInputChannel s Dev1 1 Voltage Create analog input ai analoginput nidaq Dev 1 object and add a addchannel ai 1 channel 23 2 Transition Your Code to Session Based Interface object Create a digital input and output object and add a digital input line To do this Legacy Command Session Based Command Create analog output ao analogoutput addAnalogOutputChannel nidaq Bevi s Dev1 0 Current addchannel ao 1 dio nidaq Dev1 addline dio 0 3 in digitalio S daq createSession ni addDigitalChannel s Devi PortO LineO 1 InputOnly Create counter input channels You cannot use counter channels in the legacy interface S daq createSession ni addCounterInputChannel s Devi ctrO EdgeCount St
118. DC analog output subsystem 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 bandwidth 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 base property 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 callback function A function that you construct to suit your specific data acquisition needs If you supply the callback function as the value for a callback property then the function 1s executed when the event associated with the callback property occurs Glossary 1 Glossary callback property channel channel group channel property channel skew common property configuration counter timer subsystem D A converter data acquisition session Glossary 2 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 subsyst
119. Data Acquisition Toolbox User s Guide MATLAB amp SIMULINK R201 5b e MathWorks How to Contact MathWorks Latest news www mathworks com Sales and services www mathworks com sales and services User community www mathworks com matlabcentral Technical support www mathworks com support contact us Phone 508 647 7000 The MathWorks Inc 3 Apple Hill Drive Natick MA 01760 2098 Data Acquisition Toolbox User s Guide COPYRIGHT 2005 2015 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 reproduced 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 for or through the federal government of the United States By accepting delivery of the Program or Documentation the government hereby agrees that this software or documentation qualifies as commercial computer software or commercial computer software documentation as such terms are used or defined in FAR 12 212 DFARS Part 227 72 and DFARS 252 227 7014 Accordingly the terms and conditions of this Agreement and only those rights specified in this Agreement shall pertain to and govern the use modification reproduction release performance display and disclosure of the Program and
120. Differential Sound Cards AC Coupled The InputType value determines the number of hardware channels you can add 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 nidag Devi 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 If you change the InputType value to decrease the number of channels contained by the analog input object the system returns a warning and deletes all channels Advantech and Measurement Computing Devices For Advantech 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 SingleEnded NonReferencedSingleEnded or PseudoDifferential 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 termin
121. Each segment represents a Hallelujah in the chorus The segments are annotated as 1 5 ly length y lspan 1 ly t lspan Fs hf figure plot t y max y axis tight title Signal Handel s Hallelujah Chorus vs Time xlabel Time s ylabel Amplitude markers struct xpos 0 2 0 4 0 55 0 65 0 8 string num2str 1 5 for i 1 5 annotation hf textbox markers xpos i 0 48 0 048 0 080 String markers sti end 19 5 19 Multichannel Audio Signal Handel s Hallelujah Chorus vs Time Amplitude View all available audio devices d daq getDevices d Data acquisition devices index Vendor Device ID Description 1 directsound AudioO DirectSound Primary Sound Capture Driver 2 directsound Audio1 DirectSound Microphone High Definition Audio Device 3 directsound Audio2 DirectSound HP 4120 Microphone 2 HP 4120 4 directsound Audio3 DirectSound Microphone Plantronics Audio 400 DSP 19 6 Multichannel Audio Input and Output OONOO This example uses a 5 1 channel sound system with device ID Audio8 dev dev directsound DirectSound Speakers High Definition Audio Device 1 directsound directsound directsound directsound directsound directsound d 9 Audio4 Audio5 Audio6 Audio7 Audio8 Audio9 DirectSound DirectSound DirectSound DirectSound DirectSound DirectSound Audio output subsystem supports 1 0 to 1 0 r
122. Ended s Channels InputType SingleEnded s Data acquisition session using National Instruments hardware Will run for 10 seconds 10000 scans at 1000 scans second Number of channels 1 index Type Device Channel MeasurementType Range Name 1 ai cDAQ1Mod1 aio Voltage SingleEnd 10 to 10 Volts Related Examples Acquire Analog Input Data on page 16 2 Generate Analog Output Signals on page 16 18 Acquire Counter Input Data on page 17 3 Generate Data on a Counter Channel on page 17 7 14 9 Support Package Installer Install Digilent Device Support on page 15 2 Install Multichannel Audio Device Support on page 15 4 Install National Instruments Device Support on page 15 6 15 Support Package Installer Install Digilent Device Support Use this process to add support for the Digilent Analog Discovery device to Data Acquisition Toolbox After you download and install Digilent drivers you can acquire analog input data and generate analog output data with your Digilent hardware and the session based interface Note You can use this support package only on a host computer running a version of 32 bit or 64 bit Windows Refer to the Data Acquisition Toolbox support documentation for more information on platform support 1 OpenMATLAB 2 Click Add Ons in the MATLAB Home menu 3 Select Get Hardware Support Packages re in uud Help Request Support ENVIRONME
123. Exporting Data In this section Channels on page 12 25 Measurements on page 12 26 Channels You can export this information to the MATLAB workspace a figure or a MAT file You export channel data with the Channel Exporter GUI which you open by selecting the File gt Export gt Channels menu Channel data is data associated with a hardware channel a math channel or a reference channel 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 cO and the variable name for the CHI data is c1 x Save the channel data and scaling Data destination Workspace scaling structure 7 e information as a structure Samples to export Number in display Count 1000 Save the most recent 1000 samples Selectthe channels to export T N Data 8 Variable N ES ERE IIIS MC STETIT Save the data for both channels to Hardware Hardware ch c Hardware Hardware ch c1 the variable names cO and ct M M Export Close Help The saved structure is shown below where tO is the time of the first stored sample Note that the time is negative because pretrigger data was acquired 12 25 12 softscope The Data Acquisition Oscilloscope 12 26 co co horizontalScale horizontalOffset verticalScale ve
124. Function After creating the digital I O DIO object you must add lines to it As shown by the figure in Hardware Channels or Lines on page 4 10 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 The lines must reside on the same hardware device You cannot add lines from different devices or from different subsystems on the same device Youcan 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 Youcan 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 1n the preceding section hwlines addline dio 0 7 0ut The output argument hwlines is a column vector that reflects the line group contained by dio You can display the class of hwlines with the whos command whos hwlines Add Lines to Digital I O Objects
125. 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 Amplitude 0 0 1 02 0 3 0 4 05 06 0 7 0 8 0 9 1 Time sec Amplitude 0 1 02 0 3 0 4 05 06 07 0 8 0 9 1 Time sec 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 1 39 T introduction to Data Acquisition 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 Establish the useful bandwidth of the measurement Select a sensor with sufficient bandwidth Select a low pass antialiasing analog filter that can eliminate all frequencies exceeding this bandwidth Sample the data
126. NT Get Add Ons E Loo iJ Get Hardware Support Packages Check for Product Updates 1 The Support Package Installer opens with Install from Internet selected At Support package to install select Digilent Analog Discovery Install Digilent Device Support Support Package Installer 1 Follow the support package installer prompts When prompted log into your MathWorks account Note You need write privileges for the Installation folder At any time during this process you can click Help for more information about downloading support packages 15 3 15 Support Package Installer Install Multichannel Audio Device Support Use this process to add support for multichannel audio devices to Data Acquisition Toolbox After you download and install your audio drivers you can acquire and generate data using your audio hardware and the session based interface Note You can use this support package only on a host computer running 32 bit or 64 bit Windows that Data Acquisition Toolbox supports 1 OpenMATLAB 2 Click Add Ons in the MATLAB Home menu 3 Select Get Hardware Support Packages A mm Sr 2 E Community Path Layout Help Request Support lij Parallel Y ENVIRONMENT a Get Add Ons gt Manage Add Ons i g Package Toolbox Package App IJ Get Hardware Support Packages Check for Product Updates 1 The Support Package Insta
127. 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 nidag Devi addchannel ao 0 1 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 The diagram below illustrates how you can connect a digital trigger signal to an MIO 16E Series board PFI6 WFTRIG corresponds to pin 5 8 23 8 Analog Output TTL signal MIO 16E Series board 8 24 Events and Callbacks Events and Callbacks In this section Events and Callbacks Basics on page 8 25 Event Types on page 8 25 Record and Retrieve Event Information on page 8 27 Use Callback Properties and Callback Functions on page 8 30 Events and Callbacks Basics 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 c
128. Q adaptor beginning in R2008b you will receive a warning stating that this adaptor will be removed in a future release Support for the Parallel adaptor will be removed in a future version of the toolbox If you create a Data Acquisition Toolbox object for parallel beginning in R2008b you will receive a warning stating that this adaptor will be removed in a future release See the supported hardware page at www mathworks com products daq supportedio html for more information Adaptor Specific Information To display hardware information for a particular vendor you must supply the adaptor name as an argument to daqhwinfo The supported vendors and adaptor names are given in Hardware Driver Adaptor For example to display hardware information for the winsound adaptor use the legacy interface to enter out daqhwinfo winsound out AdaptorDllName d v6 toolbox daq daq private mwwinsound d1l AdaptorDllVersion Version 2 2 R13 01 Jul 2002 AdaptorName winsound BoardNames AudioPCI Record InstalledBoardIds 0O ObjectConstructorName analoginput winsound 0O 1x26 char Examine Your Hardware Resources 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 enter out ObjectConstructorName
129. Standard waveform types include Sine Square riangle RampUp RampDown DC You can control the behavior of different waveform types using the associated properties The table shows you which properties work with the supported waveform types for Digilent devices Frequency Gain Offset Phase DutyCycle Sine 4 4 4 4 Square 4 4 4 of 4 Triangle 4 4 4 Jv 4 RampUp 4 4 4 Jv 4 RampDown v 4 Jv 4 4 DC 4 Arbitrary Jv This diagram illustrates how these properties affect a standard square waveform 20 6 Waveform Types Original DutyCycle Gain ft Phase Th 20 Waveform Function Generation Standard waveforms cannot be clipped You must keep Gain and Offset values within voltage range You cannot change Gain and Offset of arbitrary waveforms See Also DutyCycle gain Offset Phase Related Examples Generate a Standard Waveform Using Waveform Function Generation Channels on page 20 9 Generate an Arbitrary Waveform Using Waveform Function Generation Channels on page 20 11 More About Digilent Waveform Function Generation Channels on page 20 3 20 8 Generate a Standard Waveform Using Waveform Function Generation Channels Generate a Standard Waveform Using Waveform Function Generation Channels This example shows how to use the function generation channel in a session to generate a sine waveform function a
130. TLAB software you must install these components MATLAB Data Acquisition Toolbox Asupported data acquisition device the toolbox page on the MathWorks Web site lists all supported devices at http www mathworks com products daq supportedio html Software such as drivers and support libraries as required by your data acquisition device Note If you have a hardware that is not supported by Data Acquisition Toolbox see Unsupported Hardware on page 2 11 Toolbox Installation To determine if Data Acquisition Toolbox software is installed on your system type ver at the MATLAB prompt The MATLAB Command Window lists information about the software versions you are running including installed add on products and their version numbers Check the list to see if Data Acquisition Toolbox product appears For information about installing the toolbox see the MATLAB Installation documentation 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 Installation Information Hardware and Driver 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 Data Acquisit
131. 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 Making Quality Measurements 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 The expected range of the data produced by your sensor This range depends on the physical phenomena you are measuring and the output range of the sensor 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 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
132. Triggers Voice Actvaton First Trigger Signal level Volts bbb 6 0 0 1 02 03 04 05 Time sec Voice Acfvafon Second Trigger Signal level Volis bb5b5b 0 5 06 0 7 0 8 0 9 1 Time sec As described in Extract Data from the Engine on page 7 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 samples 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 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 t 0 seconds by definition the second trigger time corresponds to t and so on 7 31 7 Doing More with Analog Input 7 32 Logging Trigger 1 Trigger 2 Triggern SamplesPerTrigger ty to Un I Data stored in engine The following code modifies daqdoc5_5 so that multiple trigger data is extracted from
133. Volts Generate the data MATLAB returns once the generation is complete startForeground s Generate Signals Using Multiple Channels This example shows how to generate data from multiple channels and multiple devices using the session based interface This example generates data using channels from 16 19 16 Session Based Analog Input and Output 16 20 an NI 9263 voltage device with ID cDAQ1Mod2 and an NI 9265 current device with ID cDAQ1Mod8 Create an NI session object and add two analog output Voltage channels to cDAQ1Mod2 S daq createSession ni addAnalogOutputChannel s cDAQ1Mod2 2 3 Voltage Step 2 Add one output Current channel on cDAQ1Mod8 addAnalogOutputChannel s cDAQ1Mod8 ao2 Current ans Data acquisition session using National Instruments hardware No data queued Will run at 1000 scans second All devices synchronized using cDAQ1 CompactDAQ chassis backplane Details Number of channels 3 index Type Device Channel InputType Range Name 1 ao cDAQ1Mod2 ao2 n a 10 to 10 Volts 2 ao cDAQ1Mod2 ao3 n a 10 to 10 Volts 3 ao X cDAQ1Mod8 ao2 n a 0 to 0 020 A Specify the channel ID on NI devices using a terminal name like ao1 or a numeric equivalent like 1 Create one set of data to output for each added channel outputData 1 linspace 1 1 1000 outputData 2 linspace 2 2 1000 outputData 3 linspace 0 0 02 1000 Queue the output data queueOutpu
134. a on page 16 11 Acquire IEPE Data on page 16 13 Getting Started Acquiring Data with Digilent amp Analog Discovery on page 16 14 Using addAnaloglnputChannel Use the addAnalogInputChannel method to add a channel that acquires analog signals from a device on a National Instruments You can acquire data in the foreground or the background See About the Session Based Interface on page 14 2 for more information Acquire Data in the Foreground This example shows how to acquire voltage data from an NI 9205 device with ID cDAQ1Modl Create a session object and save it to the variable s S daq createSession ni S Data acquisition session using National Instruments hardware Will run for 1 second 1000 scans at 1000 scans second Operation starts immediately No channels have been added By default the acquisition is configured to run for a duration of 1 second to acquire 1000 scans at the rate of 1000 scans per second Acquire Analog Input Data Change the duration of the acquisition to 2 seconds s DurationInSeconds 2 0 S lt Data acquisition session using National Instruments hardware Will run for 2 seconds 2000 scans at 1000 scans second No channels have been added The acquisition now runs for 2 seconds acquiring 2000 scans at the default rate Add an analog input Voltage channel named ai0 addAnalogInputChannel s cDAQiMod1 ai0 Voltage ans Data acquisition sess
135. a Linearly on page 7 52 7 Doing More with Analog Input Configure and Sample Input Channels 7 2 In this section 7 2 Properties Associated with Configuring and Sampling Input Channels on page Configure Input Channel on page 7 2 Sampling Rate on page 7 9 Channel Skew on page 7 6 Properties Associated with 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 determine your configuration 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 Configure Input Channel You can configure your hardware input channels with the InputType property The device specific values for this property are given below InputType Property Values Vendor InputType Value Advantech Differential SingleEnded Measurement Computing Differential SingleEnded Configure and Sample Input Channels Vendor InputType Value National Instruments Differential SingleEnded NonReferencedSingleEnded Pseudo
136. a m in your working directory function plotData src event plot event TimeStamps event Data end Here src is the session object for the listener and event is a daq DataAvailableInfo object containing the data and associated timing information Acquire the data and see the plot update while MATLAB is running startBackground s When the operation is complete delete the listener delete 1h Acquire Data from an Accelerometer This example shows how to acquire and display data from an accelerometer attached to a vehicle driven under uneven road conditions Discover Devices that Support Accelerometers To discover a device that supports Accelerometers click the name of the device in the list in the Command window or access the device in the array returned by daq getDevices command This example uses National Instruments CompactDAQ Chassis NI cDAQ 9178 and module NI 9234 with ID cDAQ1Mod3 devices daq getDevices devices 3 devices Data acquisition devices Acquire Analog Input Data index Vendor Device ID Description 1 ni cDAQiMod1 National Instruments NI 9205 2 ni cDAG1Mod2 National Instruments NI 9263 3 ni cDAQiMod3 National Instruments NI 9234 4 ni cDAG1Mod4 National Instruments NI 9201 5 ni cDAG1Mod5 National Instruments NI 9402 6 ni cDAG1Mod6 National Instruments NI 9213 7 ni cDAG1Mod7 National Instruments NI 9219 8 ni cDAG1Mod8 National Instruments NI 9265 9 ni Dev1 National Instruments PCIe
137. a using a National Instruments board the appropriate version of the NI DAQ driver must be installed on your platform For further information about NI DAQmx and Traditional NI DAQ drivers see Hardware and Device Drivers on page A 3 Hardware drivers are not installed as part of the 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 Supported Hardware You can obtain most adaptors either from MathWorks or from the device vendors See the supported hardware page at www mathworks com products daq supportedio html for a list of vendors whose hardware the toolbox supports and for information about how to obtain an adaptor The toolbox provides the following adaptors The name of the vendor or device is also listed in the table 2 Using Data Acquisition Toolbox Software Adaptor Provided by the Data Acquisition Device Vendor or Device Adaptor Name Advantech advantech Measurement Computing mcc National Instruments NI nidaq DAQmx adaptors National Instruments nidaq Traditional NI DAQ adaptors Parallel port parallel Windows sound cards winsound 2 10 Notes Support for the Traditional NI DAQ adaptor will be removed in a future version of the toolbox If you create a
138. addline dio 0 3 0 out Add input lines Add two lines from port 1 to dio and configure them for input addline dio 0 1 1 in To display a summary of the digital I O object type dio Display Summary of DigitallIO DIO Object Using USB 6212 Port Parameters Port O is port configurable for reading and writing Port 1 is port configurable for reading and writing Port 2 is port configurable for reading and writing Engine status Engine not required DIO object contains line s ort Direction Out Out Out Out In In Index LineName HwLine aOahwon OWN O aot 0 Oo OC 9 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 1 1 O 1 putvalue dio Line 1 4 pval Read values To read only the input lines type gval getvalue dio Line 5 6 gval 0 0 To read both input and output lines type gval getvalue dio 2 15 2 Using Data Acquisition Toolbox Software 2 16 gval 1 1 0 1 0 0 When you read output lines getvalue returns the most recently output value set by putvalue 6 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 Altho
139. age 6 25 Status Properties The properties associated with the status of your AI object allow you to evaluate Ifthe device object is running If data is being logged to the engine or to a disk file How much data has been acquired How much data is available to be extracted from the engine The analog input status properties are given below Analog Input Status Properties Property Name Description Logging Indicate if data is being logged to memory or to a disk file Running Indicate if the device object 1s 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 1s 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 When the requested number of samples is 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 Evaluate Analog Input Object Status Display Summary You can invoke the display summary by typing an AI
140. allback functions All event types have an associated callback property Callback functions are MATLAB 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 callback function as the value for the associated callback property Refer to Create and Execute Callback Functions on page 7 47 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 8 8 Analog Output Callback Properties Event Type Property Name Run time error RuntimeErrorFcn Samples output SamplesOutputFcn SamplesOutputFcnCount Start StartFcn 8 25 8 Analog Output 8 26 Event Type Property Name Stop StopFcn Timer TimerFcn TimerPeriod Trigger TriggerFcn 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 dev
141. alog Input and Output Using RTSI You can synchronize National Instruments devices using the Real Time System Integration RTSI bus The RTSI bus connects data acquisition boards directly with no external wiring allowing you to accurately synchronize the subsystems of a device It can also synchronize multiple subsystems on multiple devices using a cable You can eliminate latency in synchronous acquisitions by coordinating the devices using the RTSI bus You can configure the system so that the start of the acquisition will trigger the start of the generation of data in the hardware For example you can configure the analog input object as the system controlling the start of the analog output object The default TriggerType is Immediate and this allows the analog input object to start when the start command is executed Set the ExternalTriggerDriveLine property to signal on the RTSI bus which triggers the analog output object ai analoginput nidaq Devi addchannel ai 0 ai ExternalTriggerDriveLine RTSIO ao analogoutput nidaq Devi addchannel ao 0 Next you should set the analog output object to receive a trigger from the same RTSI line you specified for the analog input object s ExternalTriggerDriveLine You should also set the TriggerType to HwDigital To make sure that both the analog input object and the analog output object start simultaneously you should also set the analog output object s TriggerCon
142. als 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 7 3 7 Doing More with Analog Input 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 Channels configured for pseudodifferential input are all referred to a common ground but this ground is not connected to the computer ground 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 Sampling Rate You control the rate at which an analog input subsystem converts analog data to digital data with the SampleRate property Specify SampleRate as samples per second For example to set the sampling r
143. alues that are supported for all hardware are given below Table 8 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 Getting Started with Analog Output 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 8 23 or the TriggerType reference pages Output 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 Queue 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 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
144. ange Digital Audio S PDIF Primary Sound Driver High Definition Audio I Speakers Plantronics Audio 400 DSP HP 4120 2 HP 4120 Speakers High Definition Audio Device 1 Speakers High Definition Audio Device 2 Rates from 80 0 to 1000000 0 scans sec 8 channels 1 Audio Create an audio session measurement type Device ID Audio8 1 Create a session with directsound as the vendor and add an audio output channel to it S daq createSession directsound noutch an 6 addAudioOutputChannel s dev ID 1 noutchan 2 Update the session rate to match the audio sampling rate s Rate Fs 3 Queue the same waveform to all available channels speakers If additional different voices are available these should be queued to the appropriate channels queueOutputData s repmat y 1 noutchan 4 Start finite background acquisition You should hear a sample of Handel s Hallelujah Chorus Hallelujah should be voiced five times one for each segment depicted in the figure on all channels of the speaker system 19 7 9 Multichannel Audio startForeground s 5 Close the figure close hf S Data acquisition session using DirectSound hardware No data queued Will run at 8192 scans second Number of channels 6 index Type Device Channel MeasurementType Range Name 1 audo Audio8 1 Audio 1 0 to 1 0 2 audo Audio8 2 Audio 1 0 to 1 0 3 audo Audio8 3 Audio 1 0 t
145. ar To access online help for a class or method type doc daq class name doc daq class name method name The help browser displays the reference page for the class You can also select Help gt Function Browser from the menu bar Session Based Interface Examples To access the session based interface examples in the help browser via the command line type 3 7 3 Introduction to the Session Based Interface demo toolbox data acquisition Data Acquisition Workflow The data acquisition session consists of all the steps you are likely to take when acquiring or outputting data These steps are described in the following sections Understanding the Data Acquisition Workflow on page 4 2 Create a Device Object on page 4 6 Hardware Channels or Lines on page 4 10 Configure and Return Properties on page 4 14 Acquire and Output Data on page 4 20 Clean Up on page 4 24 4 Data Acquisition Workflow Understanding the Data Acquisition Workflow In this section Overview on page 4 2 Real Time Data Acquisition on page 4 3 Data Acquisition Workflow on page 4 4 Overview The data acquisition workflow 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
146. ar the Mute check box for these sound devices CD A 20 Legacy Interface Using All Devices Microphone Line 3 To play WAV files clear the Mute check box for the Wave sound device Play Control 3 cf x Options Help Play Control Wave MP3 Microphone CD Audio Line In Balance Balance Balance Balance Balance Vat mls Fe e Fe ae T Ie pet Volume Volume Volume Volume Volume Mute all T Mute T Mute T Mute Emu OKx Audio B800 If you don t see the CD microphone or Wave Output controls in the Volume Control panel select Properties from the Options menu to modify the playback properties Properties L2 x Mixer device pemean Adjust volume for Playback C Recording ther z Show the following volume controls V Volume Control CD Wave Synthesizer To verify if the CD and microphone are enabled for recording click the Recording option 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 A 21 A Legacy Interface Using All Devices Properties L2 x Mixer device audioPCI Mixer Adjust volume for C Playback C Gther z Show the following volume controls V Microphone Line Auxiliary X ois Cancel The Recording Control panel is shown below You
147. ardware Measurement Computing Hardware Note You can use hardware from this vendor only with 32 bit MATLAB You can install a 32 bit MATLAB on 64 bit Windows For more information see this technical bulletin For boards that do not have a channel gain list an error occurs at start if all the channel input ranges are not the same or the channel scan order is not contiguous However if the ClockSource property value is set to sof tware this rule does not apply You should configure the SampleRate property with the setverify function just before starting the hardware Note that the SampleRate value is dependent upon the number of channels added to the device object For boards that do not support continuous background transfer mode i e the board does not have hardware clocking the only available ClockSource property value is software When running at a sampling rate of 5000 Hz or higher and with a TransferMode property value of InterruptPerPoint there may be a considerable decline in system performance Most boards do not support simultaneous input and output However if software clocking is used then this limitation does not apply To use hardware digital triggers with the PCI DAS4020 12 board you must first configure the appropriate trigger mode with InstaCal Expansion boards are not supported This includes the CIO EXP family of products MEGA FIFO hardware is not supported B 5 B Windows Soun
148. art ai wait slightly longer than the duration of the acquisition times the number of triggers for the acquisition to complete wait ai ai TriggerRepeat 1 duration 1 11 9 11 Saving and Loading 11 10 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 5 Clean up When you no longer need ai you should remove it from memory and from the MATLAB workspace delete ai clear ai Retrieve 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 Retrieve 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 Plot the data and label the figure axes subplot 211 plot data xlabel Samples ylabel Signal Volts subplot 212 plot time data xlabel Time seco
149. art the object start ai startForeground s for operations that block MATLAB when running startBackground s for operations that run without blocking MATLAB Set rate of acquisition ai SampleRate 48000 s rate 48000 Specify an external trigger ai TriggerType HwDigital addTriggerConnection s External Dev3 PFIO StartTrigger Specify a range of input signals ai Channel InputRange 5 5 ch addAnalogInputChannel s Dev1 1 Voltage ch Range 5 5 Acquire Analog Data Legacy Interface Using the legacy interface you find hardware available to your system create an analog input object and start acquisition 1 Find hardware available to your system d daqhwinfo Create an analog input object and add a channel using a National Instruments device with ID Dev1 ai analoginput nidaq addchannel ai 1 Dev1 23 3 23 Transition Your Code to Session Based Interface 23 4 3 Set the sample rate to 8000 and start the channel ai SampleRate 8000 start ai Session Based Interface Using the session based interface you create a vendor session and add channels to the session You can use any device or chassis from the same vendor available to your system and can add a combination of analog digital and counter input and output channels All the channels operate together when you start the session 1 Find hardware available
150. ase addresses are not accessible by the toolbox Note You can use parallel port only on 32 bit Windows XP systems Most PCs that support the MATLAB software 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 the MATLAB workspace Therefore other applications or other instances of the MATLAB application can access the same parallel port which can result in a conflict Administrator Privileges for Parallel Port Pins Accessing the individual pins of the parallel port under Windows 2000 and Windows XP is a privileged operation Data Acquisition Toolbox software installs a driver called winio sys that provides access to the parallel port pins Normally only users with administrator privileges can do this To allow users without administrator privileges to use the parallel port from Data Acquisition Toolbox software 1 Login to your machine as the administrator 2 Start the MATLAB software Digital I O Objects 3 At the MATLAB Command Window type daqhwinfo parallel 4 Minimize the MATLAB Command Window 5 Onthe desktop select My Computer and right click Choose Properties from the menu that appears 6 Inthe dialog box that appears click the Hardware tab and click the Device Manager button 7 Inthe window that appears select View Show Hidden Devices and expand
151. associated with the hardware math and reference channels that are listed in the pane For descriptions of all channel properties click the Help button of the appropriate GUI editor Channel Pane Properties You can change the characteristics of the controls and labels that make up the pane 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 4l display2 Triggers Channel Scaling Select Channel Scaling Editthe selected scope components properties HorizontalOffsetSensitivity 0 003 HorizontalScaleSensitivity 0 01 Name Channel Scaling L ShowName PE True VerticalOffsetSensitivity 0 006 VerticalScaleSensitivity 0 01 OK Cancel Help Click Help to view property descriptions Channel Data and Properties Channel Properties You can change the characteristics of the hardware math and reference channels that are listed in the pane by configuring their channel properties You can access the channel properties these two ways Property Inspector Place the mouse cursor in the Channel Scaling pane right click and select Edit Properties from the menu Channel Editor GUI Select Channel from the Edit menu and then choose the Channe
152. at a rate at least twice that of the filter s upper cutoff frequency 1 40 Getting Command Line Function Help Getting Command Line Function Help To get command line function help you should use the daghelp function For example to get help for the addchannel function type help addchannel However Data Acquisition Toolbox software provides overloaded versions of several MATLAB functions That is it provides 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 Data Acquisition Toolbox software 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 1 41 T introduction to Data Acquisition Selected Bibliography 1 Transducer I
153. at occurs before the trigger executes String 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 Window Trigger 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 Retrieve Event Information Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB Suppose you want to examine the events logged for the example given by Queue Data with putdata on page 8 17 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 8 29 8 Analog Output 8 30 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 sh
154. at 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 Display Hardware Info from the context menu Getting Help Getting Help In this section The daqhelp Function on page 2 25 The propinfo Function on page 2 25 The daqhelp Function If you are using CompactDAQ devices or counter timer devices see Counter and Timer Input and Output You can use the daghelp function to Display help for functions and properties List 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 help enter 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 DAQ Help from the context me
155. ata a trigger must occur You configure an analog input trigger with the TriggerType property For a detailed description of triggers see Configure Analog Input Triggers on page 7 19 Acquire Data 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 Window until all the requested data is returned to the workspace You can extract data any time after the trigger occurs 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 You can read more detail in the getdata reference page You can log data to disk with the LoggingMode property You can replay data saved to disk with the daqread function Refer to Log Information to Disk on page 11 5 for more information about LoggingMode and daqread Stop Analog Input Object An analog input object can stop under one of these conditions Youissue the stop function The requested numbe
156. ata acquisition devices index Vendor Device ID Description 1 ni Dev1 National Instruments USB 6255 2 ni Dev2 National Instruments USB 6363 Create a session and add four lines from port 0 on Dev1 S daq createSession ni addDigitalChannel s Devi PortO Line0 3 InputOnly ans Data acquisition session using National Instruments hardware Clocked operations using startForeground and startBackground are disabled Only on demand operations using inputSingleScan and outputSingleScan can be done Number of channels 4 index Type Device Channel MeasurementType Range Name 1 dio Devi portO lineO InputOnly n a 2 dio Devi portO linei InputOnly n a 3 dio Devi portO line2 InputOnly n a 4 dio Devi portO line3 InputOnly n a Acquire digital data in hexadecimal values binaryVectorToHex inputSingleScan s ans C Control Stepper Motor using Digital Outputs Control Stepper Motor using Digital Outputs This example shows how to control a stepper motor using digital output ports Discover Devices Supporting Digital Output To discover a device that supports digital output Issue daq getDevices in the Command window Click on the device name in the list returned by the command devices daq getDevices devices Data acquisition devices index Vendor Device ID Description 1 ni cDAQ1iMod1 National Instruments NI 9205 2 ni cDAG1Mod2 National Instruments NI 9263 3 ni cDAQ1iMod3 National Instruments NI 9234
157. ate for each channel of your National Instruments board to 100 000 samples per second 100 kHz ai analoginput nidaq Dev addchannel ai 0 1 ai SampleRate 100000 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 Ifthe rate is within the range of valid values then the engine automatically selects a valid sampling rate Ifthe rate is outside the range of valid values then an error is returned After setting a value for SampleRate find out the actual rate set by the engine ActualRate ai SampleRate Configure and Sample Input Channels 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 ai SampleRate ValidRates ConstraintValue ans 1 0e 005 0 0000 2 0000 The maximum rate at which channels are sampled depends on the type of hardware you are using The maximum board rate determines the maximum sampling rate for each channel if you are using simultaneous sample and hold SS H hardware such as a sound card 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 r
158. ate of 48 0 kHz then the maximum sampling rate per channel is 48 0 kHz ai analoginput winsound addchannel ai 1 2 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 You can apply the following formula to calculate the maximum sampling rate per channel Maximum sampling rate per channel Maximum board mate Number of channels scanned For example suppose you create the analog input object ai for a National Instruments board and add ten 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 Dev ai InputType SingleEnded addchannel ai 0 9 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 7 Doing More with Analog Input 7 6 including the settling time the gain and the channel skew See Channel Skew on page 7 6 for more information The hardware clock governs the list of valid sample rates on the device Most devices offer a fixed speed hardware clock used to drive the timing of an acquisition In order to achieve a required sample rate there is a programmable divider set from 1 to 65536 This limits the device to 65535 possible sample rates Fo
159. ational Instruments hardware Will run for 1 second 10000 scans at 10000 scans second Operation starts immediately No channels have been added Add an analog output Voltage channel addAnalogOutputChannel s cDAQ1Mod2 0 Voltage ans Generate Analog Output Signals Data acquisition session using National Instruments hardware No data queued Will run at 1000 scans second Number of channels 1 index Type Device Channel MeasurementType Range Name 1 ao cDAQ1Mod2 ao0 Voltage 10 to 10 Volts Specify the channel ID on NI devices using a terminal name like a01 or a numeric equivalent like 1 Create the data to output outputData linspace 1 1 2200 Queue the data queueOutputData s outputData The duration changes to 0 22 seconds based on the length of the queued data and the specified scan rate When the session contains output channels duration and number of scans become read only properties of the session The number of scans in a session is determined by the amount of data queued and the duration is determined by s ScansQueued s Rate Display the session object to see this change S s Data acquisition session using National Instruments hardware Will run for 2200 scans 0 22 seconds at 10000 scans second All devices synchronized using cDAQ1 CompactDAQ chassis backplane Details Number of channels 1 index Type Device Channel InputType Range Name 1 ao X cDAQ1Mod2 ao0 n a 10 to 10
160. board Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB 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 Note Data Acquisition Toolbox software does not directly support buffered DIO or handshaking latching However you can write your own 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 Note Data Acquisition Toolbox software does not support the counter timer subsystem that is built into a number of data acquisition devices Digital O Objects Digital I O Objects In this section Create a Digital I O Object on page 10 3 Parallel Port on page 10 4 Create 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 When using NI DAQmx this is usually a string such as D
161. by the component with the worst accuracy 1 33 T introduction to Data Acquisition 1 34 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 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
162. c 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 devices are discussed in Device Specific Hardware Triggers on page 8 23 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 output object for continuous output by using an immediate trigger and setting RepeatOutput to inf Configure Analog Output Triggers To see how to set up continuous analog input acquisitions refer to the Continuous Acquisitions Using Analog Input example Manual Trigger If TriggerType is Manual the trigger occurs immediately after the trigger function is issued Execute Triggers For an analog output trigger to occur you must follow these steps Queue data in the engine Configure the appropriate trigger properties Issue the start function Aa O N Issue the trigger function if TriggerType is Manual Once the
163. ces pm L JO INSTRUMENTS NI PXle 1062Q system Timing Slot Homogeneous synchronization You can synchronize PXI 447x devices homogeneously as long as one device is plugged into the system timing slot of a PXI chassis Heterogeneous synchronization Youcan synchronize a PXI 447x device with a PXI 446x device when the 446x is plugged into the system timing slot of a PXI chassis Youcannot synchronize PXI 447x devices with PXI 449x devices Youcannot use hybrid slot compatible 446x devices DSA Device Compatibility Table 446x Series 447x Series 449x Series 446x PXI chassis only Series 22 15 22 Session Based Synchronization 22 16 446x Series 447x Series 449x Series Standard 446x device not hybrid slot compatible 446x device in system timing slot 447x PXI chassis only PXI chassis only X Series Standard 446x device not One device in system hybrid slot compatible timing slot 446x device in system timing slot 449x 4 X 4 Series Synchronize Dynamic Signal Analyzer PXI Devices This example shows how to acquire synchronized data from two Dynamic Signal Analyzer DSA PXI devices NI PXI 4462 and NI PXI 4461 Create an acquisition session and add one voltage analog input channel from each of the two PXI devices S daq createSession ni addAnalogInputChannel s PXIiSlot2 0 Voltage addAnalogInputChannel s
164. ces go to the National Instruments Measurement amp Automation Explorer NI MAX and examine the devices installed on your CompactDAQ chassis Receive one of the following errors No data acquisition devices available Goto NI MAX and examine the devices installed on your CompactDAQ chassis If you cannot see your devices in NI MAX check to see if you have turned on and connected your chassis Ifyou have turned on and connected your chassis and issued daqreset and you can see the devices in NI MAX reinstall Data Acquisition Toolbox software e The requested subsystem AnalogInput does not exist on this device You could be Using an output device to add input channels See daq getDevices to learn more about an installed device Using an unsupported device See Supported Hardware on page A 2 The requested subsystem AnalogOutput does not exist on this device You could be Using an input device to add output channels See daq getDevices to learn more about an installed device Using an unsupported device See Supported Hardware on page A 2 If you are using NI 9402 with the counter timer subsystem with the cDAQ 9172 chassis plug the module into slots 5 or 6 only If you plug the module into one of the other slots it will not show any counter timer subsystem If you are using an Ethernet CompactDAQ chassis reserve the chassis in National Instruments Measurement amp Automation Explore
165. ces that require the session based interface daghwinfo nidaq Warning Devices were detected that require the DAQ Session Based Interface For more information see documentation on the session based interface ans AdaptorDllName 1x103 char AdaptorDllVersion 3 0 R2011b AdaptorName nidaqg BoardNames 1x13 cell InstalledBoardIds 1x13 cell ObjectConstructorName 13x3 cell Refer to About the Session Based Interface on page 14 2 to learn how to communicate with CompactDAQ devices Is My NI DAQ Driver Supported Data Acquisition Toolbox software 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 Data Acquisition Toolbox software refer to the product page on MathWorks website at http www mathworks com products daq supportedio html and click the link for this vendor To see your installed driver version in the session based interface type v daq getVendors V Number of vendors 2 Session Based Interface Using National Instruments Devices index ID Operational Comment 1 ni true National Instruments 2 digilent false Click here for more info Properties Methods Events Additional data acquisition vendors may be available as downloadable support packages Open the Support Package Installer to install additional vendors If the version in the DriverVersion field
166. cific 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 winsoundO AO Stop event occurred at 13 00 25 for the object winsoundO AI 8 37 Advanced Configurations Using Analog Input and Analog Output Start Analog Input and Output Simultaneously on page 9 2 Synchronize Analog Input and Output Using RTSP on page 9 4 9 Advanced Configurations Using Analog Input and Analog Output Start Analog Input and Output Simultaneously Using Data Acquisition Toolbox software you can simultaneously start analog input and analog output For example you can create an analog input object ai and an analog output object ao for a sound card and add one channel to each device object ai analoginput winsound addchannel ai 1 ao analogoutput winsound addchannel ao 1 Queue data in the engine and start the device objects By default the TriggerType is Immediate and this allows the trigger to execute immediately after start is issued The Start command will configure the objects and execute the trigger sequentially leading to a delay between the start of the two operations data zeros 4000 1 putdata ao data start ai ao When you pass ai and ao to start as an array the first object in the array is configured and triggered then the second object is configured and triggered This is done serially and
167. cify one or more of these parameters A trigger condition and trigger condition value The number of times to repeat the trigger A trigger delay A callback function to execute when the trigger event occurs 7 19 7 Doing More with Analog Input Properties associated with analog input triggers are as follows 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 TriggerFecn Specify the callback function to execute when a trigger occurs TriggerChannel Specify the channel serving as the trigger source TriggerCondition Specify the condition that must be satisfied before a trigger executes TriggerConditionValue Specify one or more voltage values that must be satisfied before a trigger executes TriggerDelay Specify the delay value for data logging TriggerDelayUnits Specify the units in which trigger delay data is measured TriggerRepeat Specify the number of additional times the trigger executes TriggersExecuted Indicate the number of triggers that execute TriggerType 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 7 41 Define Trigger Types and Conditions This section contains the follo
168. circumstances the callback function is not guaranteed to complete execution until sometime after Logging 1s set to On Record and Retrieve 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 7 4 Analog Input Event Information Stored in EventLog Event Type Type Field Value Data Field Value Data missed DataMissed AbsTime RelSample Input overrange OverRange AbsTime RelSample Events and Callbacks Event Type Type Field Value Data Field Value Channel OverRange Run time error Error AbsTime RelSample String Start Start AbsTime RelSample Stop Stop AbsTime RelSample Trigger Trigger AbsTime RelSample Channel Trigger Samples acquired events and timer events are not stored in EventLog Note Unless a run time error occ
169. cise accurate measurement To overcome these obstacles you need to experiment with different hardware and software configurations In other words you need to perform multiple data acquisition trials 1 Introduction to Data Acquisition Data Acquisition System In this section Overview on page 1 8 Sensors on page 1 12 Data Acquisition Hardware on page 1 10 Signal Conditioning on page 1 15 The Computer on page 1 17 Software on page 1 17 Overview Data Acquisition Toolbox in conjunction with the MATLAB technical computing environment gives you the ability to measure and analyze 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 Components Description 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 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 mic
170. cord data you use the sound card s analog input subsystem When you play data back you use the sound card s analog output subsystem If you successfully record and play data back your sound card works You can record data from A microphone A CD player To test your sound card enable its ability to record and play data In the Windows desktop 1 Select Start gt Settings gt Control Panel 2 Double click Sounds and Audio Devices 3 Enable both data play back and recording A 19 A Legacy Interface Using All Devices Sounds and Audio Devices Properties 2 x Volume Sounds Audio Voice Hardware M Sound playback Default device Emut OKx Audio B800 Y Vome aerea M Sound recording 4A Default device 4 Emu OKs Audio B800 m Volume Advanced MIDI music playback Sis Default device a Microsoft GS Wavetable Sw Synth m Volume About Use only default devices OK Cancel Apply Use the Windows Sound Recorder panel to record data and then play it back 1 Select Start gt Programs gt Accessories gt Entertainment gt Sound Recorder PR ELO Recorder PRISES File Edit Effects Help Position Length 0 00 sec 0 00 sec Play button Record button Make sure that your microphone or CD player is enabled for recording and playback 1 Select Start gt Programs gt Accessories gt Entertainment gt Volume Control 2 Cle
171. ct 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 ai SampleRate 48000 Configure Analog Input Properties 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 You can apply the following formula to calculate the maximum sampling rate per channel Maximum sampling rate per channel Maximum board mte Number of channels scanned For example suppose you create the analog input object ai for a National Instruments board and add ten 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 Dev ai InputType SingleEnded addchannel ai 0 9 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 settling time the gain and the channel skew See Channel Skew on page 7 6 for more information The hardware clock governs the list of valid sample rates on the device Most devices offer a fixed speed hardware clock used to drive the timing of an acquisition In order to achieve a required sample rate there is a programmable
172. ct is executing you can output data Glossary 3 Glossary FIFO buffer full duplex input range interrupts legacy interface line line group line properties logging noise onboard clock Glossary 4 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 1s acquired or when multiple samples are acquired The interface available with Data Acquisition Toolbox works with all supported data acquisition hardware except CompactDAQ devices and devices using the counter timer subsystem Using this interface you create data acquisition objects with these commands analoginput analogoutput digitalio A component of a digital I O subsystem that you can read digital values from or write digital values to The collection of lines contained by a digital I O object Properties that are configured for individual lines A state of Data Acquisition Toolbox software where an analog input object stores acquired data
173. d 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 AI SampleRate 8000 ActualRate AI SampleRate AI SamplesPerTrigger duration ActualRate AI TriggerType Manual blocksize AI SamplesPerTrigger Fs ActualRate 6 17 6 Getting Started with Analog Input 6 18 See The Sampling Rate for more information 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 to the sound card start AI trigger AI wait AI duration 1 The wait function pauses MATLAB until either the acquisition completes or the time out elapses whichever comes first If the time out elapses an error occurs Adding 1 second to the duration allows some margin for the time out 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 Analyze Data Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on
174. d Cards Windows Sound Cards B 6 Note You can use hardware from this vendor only with 32 bit MATLAB You can install a 32 bit MATLAB on 64 bit Windows For more information see this technical bulletin The maximum sampling rate depends on the StandardSampleRates property value If StandardSampleRates is On the maximum SampleRate property value is 44100 If StandardSampleRates is Off the maximum SampleRate property value is 96000 if supported by the sound card For some sound cards that allow nonstandard sampling rates certain values above 67 000 Hz will cause your computer to hang If you are acquiring data when StandardSampleRates is Off one of these messages may be returned to the command line depending on the specific sound card you are using Invalid format for device winsound occurs when the sound card does not allow for any nonstandard value Device Winsound already in use occurs when a nonstandard sampling rate 1s specified and the device takes longer than expected to acquire data Managing Your Memory Resources Manage memory allocation on your system to temporarily store data that is used by an analog input or output subsystem This topic tells you C whatis Memory Allocation What is 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 Data Acquisition Toolbox software allocates
175. d Hardware page on the Mathworks Web site Use this table to choose an interface based on how you want to use your National Instruments device To choose an interface based on device type see Interface By Device Vendor table National Instruments Usage Based on Functionality Functionality Session Based Interface Legacy Interface Analog Input Voltage 4 Current Temperature Accelerometer Bridge Analog Output SISISISIS KS S Voltage lt Current Counter Timer Input and Output Edge count Pulse width Frequency Position Digital Input and Output eese ees ce ee es Multi device acquisition and generation 3 5 3 Introduction to the Session Based Interface 3 6 Functionality Session Based Interface Legacy Interface Simulink Blocks 4 Getting Help Getting Help In this section Command Line Help on page 3 7 Online Help on page 3 7 Session Based Interface Examples on page 3 7 Command Line Help To access command line help for the session based interface type help sessionbasedinterface To access command line help for a class or method type help daq class name help daq class name method name Online Help To access online help for the session based interface via the command line type doc daq You can also select Help gt Product Help from the menu b
176. d Output Data 4 20 In this section Device Object States on page 4 20 Start the Device Object on page 4 21 Log or Send Data on page 4 21 Stop the Device Object on page 4 22 Device Object States As data is being transferred between the MATLAB workspace and your hardware you can think of the device object as being in a particular state Two types of states are defined for Data Acquisition Toolbox software Running For analog input objects running means that data 1s 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 means 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 logging means that data acquired from an analog input subsystem is being stored in the engine or saved to a disk file The logging state 1s 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 1s 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 Run
177. d at a specific rate in the way that data 1s 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 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 10 4 Digital 1 O Timer Event Properties Property Name Description Running Indicate if the device object is running TimerFocn Specify the callback function to execute whenever a predefined period of time passes 10 19 10 Digital Input Output 10 20 Property Name Description TimerPeriod Specify the period of 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 Some timer events might not be processed if
178. dAnalogInputChannel addAnalogOutputChannel addAudioInputChannel addAudioOutputChannel addCounterInputChannel addCounterOutputChannel addDigitalChannel addlistener 5 3 D Session Based Interface Workflows daq createSession daq getDevices daq getVendors delete queueOutputData startBackground startForeground Properties AutoSyncDSA DurationInSeconds EnhancedAliasRejectionEnable IsContinuous NumberOfScans Rate RateLimit ScansAcquired ScansOutputByHardware ScansQueued 5 4 Analog Input and Output Workflow Analog Input and Output Workflow Once you create a session use this workflow to set up analog channels and acquire and generate data Discover supported devices daq getDevices Create DA addAnalogInputChannel addAnalogOutputChannel Queue output data queueOutputData oreground atior startForeground inputSingleScan i OutputSingleScan D startBackground No St r Yes to elete listene hoanl delete D Session Based Interface Workflows See Also Functions addAnalogInputChannel addAnalogOutputChannel addlistener daq createSession daq getDevices delete inputSingleScan outputSingleScan queueOutputData startBackground startForeground 5 6 Digital Input and Output Workflow Digital Input and Out
179. 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 Manage Output Data on page 8 15 and in the functions 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 8 Analog Output 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 Define a Trigger on page 8 6 and Configure Analog Output Triggers on page 8 19 Stop Analog Output Object An analog output object can stop under one of these conditions You issue the stop function The queued data is output A run time hardware error occurs A time out 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
180. device you can import the clock to the session External digital DAQ Session circuit Digital subsystem If your device does not have an on board clock you can Import a clock from an external source See Acquire Clocked Digital Data with Imported Clock on page 18 7 for more information Generate a clock from a Counter Output subsystem in your session and import that clock See Acquire Digital Data Using Counter Channels on page 18 11 for more information Sharea clock from the analog input subsystem See Acquire Clocked Digital Data with Shared Clock on page 18 9 for more information Access Digital Subsystem Information This example shows how to access the device s digital subsystem information and find line and port information using daq getDevices Find devices connected to your system and find the ID for NI 6255 d daq getDevices dz Data acquisition devices index Vendor Device ID Description Digital Subsystem Channels 2 ni Dev2 National Instruments USB 6363 View the subsystem information for Dev1 with index 1 subs d 1 Subsystems View the digital subsystem information which is the third subsystem on this device subs 3 ans Digital subsystem supports 24 channels portO lineO port2 line7 InputOnly OutputOnly Bidirectional measurement types 18 5 18 session Based Digital Operations Acquire Non Clocked Digital Data This example shows how to read data usi
181. dition to PositiveEdge ao TriggerType HwDigital ao HwDigitalTriggerSource RTSIO ao TriggerCondition PositiveEdge You should start your analog output object first and then the analog input object The analog output object starts but will not send data until the analog input object starts putdata ao zeros 1000 1 start ao start ai When the analog input object is started it will send a pulse on the RTSI bus The analog output object detects this pulse and starts almost simultaneously Synchronize Analog Input and Output Using RTSI For more information on starting analog input objects and analog output objects simultaneously refer to the Data Acquisition Toolbox example Synchronizing Analog Input and Output Using RTSI 9 5 Digital Input Output 10 Digital Input Output Digital I O Subsystems 10 2 Digital I O DIO subsystems are designed to transfer digital values to and from hardware These values are handled either as single bits or ines 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 1s required for performing advanced DIO operations Data Acquisition Toolbox software 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
182. ditioning includes amplification filtering electrical isolation and multiplexing 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 acquisition 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 Data Acquisition Toolbox software supports analog input analog output and digital I O subsystems Glossary trigger event 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 Glossary 7
183. divider set from 1 to 65536 This limits the device to 65535 possible sample rates For instance with a 100 000Hz clock if you request 1 200 samples per second you can set the divider to either 83 or 84 This setting results in a sample rate of either 1 204 82 100 000 83 or 1 190 48 100 000 84 Notes 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 for more information When you change the SampleRate value and the Buf f eringMode property is Auto the engine recalculates the Buf feringConfig property value BufferingConfig indicates the memory used by the engine 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 trigger 6 11 6 Getting Started with Analog Input type with the TriggerType property The TriggerType values that are supported for all hardware are given below 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 1s satisfied Trigger conditions are given by the TriggerCondition prope
184. dled by the toolbox then the hardware specific error message is displayed Events and Callbacks 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 time outs 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 Use SamplesAcquiredFcn to trigger an event each time a specified number of samples is acquired To process samples at regular time intervals use the TimerFcn property However if you are performing a CPU intensive task with the data then system performance might be adversely affected Start Event A start event is generated immediately after the start function is issued This event executes the callback function specified for StartFcn When StartFocn 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
185. e You can display the values of these properties for ao with the get function ao Name Type ans nidaqmxDev1 AO Analog Output Add Channels to an Analog Output Object After creating the analog output object you must add hardware channels to it As shown by the figure in Hardware Channels or Lines on page 4 10 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 Hardware Channel IDs to the MATLAB Indices on page 4 11 a channel group consists of a mapping between hardware channel IDs and MATLAB indices When adding channels to an analog output object you must follow these rules The channels must reside on the same hardware device You cannot add channels from different devices or from different subsystems on the same device 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 8 Analog Output chans addchannel ao 0 1 The output argument Chans is a channel object that reflects the channel array contained by ao You can dis
186. e analog input object ai and the analog output object ao for a sound card 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 winsoundO AO To create the column array y y aij ao Note that you cannot create a matrix of device objects For example you cannot create the matrix z ai ao ai ao 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 x SampleRate 44100 Refer to the functions to see which one 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 fora sound card and then make a copy of ai ai analoginput winsound newai ai Create a Device Object 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 ai SampleRate 22050 ans 22050 As shown below ai and newai return the same property value because
187. e clock and the bit number for serial data s transfer if isempty clock clock 1 end s bitNumber is used to index into the serial data that needs to be sent if isempty bitNumber bitNumber 0 end s Execute all calls to the function clock clock 18 25 18 session Bosed Digital Operations 18 26 When the function reaches the end of the serial data stop reset the s persistent variables to initial state and delete the timer if bitNumber numel serialData stop obj Reset variables for next run bitNumber 0 clock 1 disp Stopping software timer Command sent return end s Output the serial data and clock in your session outputSingleScan s clock serialData bitNumber end Delete the timer after all the serial bits are output pause 1 delete t Multichannel Audio 9 Multichannel Audio Multichannel Audio Input and Output 19 2 You can acquire and generate audio signals using one or more available channels of a supported audio device You can also simultaneously operate channels on multiple supported audio devices Currently Data Acquisition Toolbox supports audio channels for devices that work with DirectSound interface Using the session based interface you can Acquire and generate audio signals either in sequence or as separate operations Acquire and generate signals in parallel where the signals may share the start time Acquire the data in the back
188. e 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 ai ao TriggerType Manual ai ManualTriggerHwOn Trigger Configure ai for continuous acquisition call the callback function qnoredata whenever 1000 samples are output and call daqcallback when ai and ao stop running ai SamplesPerTrigger inf ao SamplesOutputFcn qmoredata ai ao SamplesOutputFcnCount 1000 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 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 Start Multiple Device Objects Note You cannot trigger device objects 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 InitialTriggerTime delta abs aotime aitime sprintf d delta 6 ans 2 28881 8e 005 Note that this number depends on the spe
189. e devices RTDs require external voltage or current excitation Data Acquisition System Signal conditioning modules for these sensors usually provide the necessary excitation RTD measurements are usually made with a current source that converts the variation 1n 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 memory 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 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
190. e getsample function or output single values using the putsample function 2 19 2 Using Data Acquisition Toolbox Software 2 20 Configure the ClockSource property to Software Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB Examples The toolbox includes a large collection of examples which you can access through the Help browser Note that the analog input and analog output 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 Examine Your Hardware Resources Examine Your Hardware Resources In this section Using the daqhwinfo Function on page 2 21 General Toolbox Information on page 2 21 Adaptor Specific Information on page 2 22 Device Object Information on page 2 23 Using the daqhwinfo Function You can examine the data acquisition hardware resources visible to the toolbox with the daqhwinfo function Hardware resources include installed boards hardware drivers and adaptors The information returned by daqhwinfo depends on the supplied arguments and is divided into three categories described in this section If you configure hardware parameters using a vendor tool such as National Instruments Measurement and Automation Explorer or Measure
191. e 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 Sensor Bandwidth on page 1 14 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
192. e 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 AC 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 Configure the input channels in differential mode Refer to Channel Configuration for more information about channel configuration 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
193. ect are listed below Table 4 1 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 This applies only to Traditional NI DAQ boards Note The Traditional NI DAQ adaptor will be deprecated in a future version of the toolbox If you create a Data Acquisition Toolbox object for Traditional NI DAQ adaptor in R2008b you will receive a warning stating that this adaptor will be removed in a future release See the supported hardware page at www mathworks com products daq supportedio html for more information 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 Hardware Channels or Lines 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 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 contain
194. ed ai SamplesAcquiredFcnCount 1000 ai SamplesAcquiredFcn mycallback Alternatively you can specify the callback function as a cell array ai SamplesAcquiredFcn mycallback 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 7 4 Analog Input Event Information Stored in EventLog 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 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 Events and Callbacks 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
195. ed 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 Configure and Return Properties Configure Property Values You configure property values 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 the function properties 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 Return Property Names and Property Values on page 4 16 Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB Common Properties You can configure a single property value ai TriggerType Manual 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 chi ai Channel 1 chi SensorRange 2 2 To configure values for multiple channel or line properties chi SensorRange 2 2 ch1 ChannelName Chant Specify Property Names Device object property names are pr
196. ee 16 11 Acquire IEPE Data 0 0 0 0 ce ee 16 13 Xiv Contents Getting Started Acquiring Data with Digilent amp Analog Discoyeryb 5225 cr va oer SuSE aii 16 14 Generate Analog Output Signals 16 18 Use addAnalogOutputChannel 5 16 18 Generate Signals in the Foreground 16 18 Generate Signals Using Multiple Channels 16 19 Generate Signals in the Background 16 20 Generate Signals in the Background Continuously 16 21 Getting Started Generating Data with Digilent amp Analog Discovery 522 iovis eae URN ERU IIR E 16 22 Acquire Data and Generate Signals Simultaneously 16 25 Session Based Counter Input and Output 17 Analog and Digital Counters 0 000005 17 2 Acquire Counter Input Data lille 17 3 addCounterInputChannel llle 17 3 Acquire a Single EdgeCount 0 0 0 0 00 cee 17 3 Acquire a Single Frequency Count llle 17 4 Acquire Counter Input Data in the Foreground 17 5 Generate Data on a Counter Channel 17 7 Use addCounterOutputChannel 17 7 Generate Pulses on a Counter Output Channel 17 7 Session Based Digital Operations 18 Digital Subsystem Channels 0 00 00 es 18 2 Digital Clocked Operations 0 0 00 e eens 18 2 Access Digital Subsystem Information
197. ee your adaptor in the list of available adaptors refer to Troubleshooting Your Hardware Note If you cannot see your device in the list of available devices refer to Troubleshooting Your Hardware Each analog input object is associated with one board and one analog input subsystem For example to create an analog input object associated with a National Instruments board with device ID 1 ai analoginput nidaq Dev 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 Create an Analog Input Object 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 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 ai Name ans nidaqmxDev1 AI ai type ans Analog Input 6 Getting Started with Analog Input Add Channels to an Analog Input Object 6 4 In this section Channel Group on page 6 4 Reference Individual Hardware Channels on page 6 5 Add Channel
198. em 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 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 frequency and period measurement and pulse train generation This subsystem is not supported by Data Acquisition Toolbox software 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 Glossary data block device object device specific property differential input digital 1 O subsystem DMA engine engineering units properties event execution The smallest slice of memory that the data acquisition
199. ent S z Data acquisition session using Digilent Inc hardware Will run for 1 second 10000 scans at 10000 scans second No channels have been added Add an analog input channel Add an analog input channel with device ID AD1 and channel ID 1 Set the measurement type to Voltage ch addAnalogInputChannel s ADi 1 Voltage ch Data acquisition analog input voltage channel 1 on device AD1 Coupling DC TerminalConfig Differential Range 25 to 25 Volts Name ID 1 Device 1x1 daq di DeviceInfo MeasurementType Voltage Set session and channel properties Set the sampling rate to 300kHz and the channel range to 2 5 to 2 5 volts Set the duration to 0 5 seconds s Rate 300e3 s Channels Range 2 5 2 5 s DurationInSeconds 0 5 16 15 16 Session Based Analog Input and Output 16 16 S Data acquisition session using Digilent Inc hardware Will run for 0 5 seconds 150000 scans at 300000 scans second Number of channels 1 index Type Device Channel MeasurementType Range Name 1 ai AD1 1 Voltage Diff 2 5 to 2 5 Volts Acquire a single sample Acquire a single scan on demand measuring the data and trigger time singleReading triggerTime s inputSingleScan singleReading 0 0104 triggerTime 7 3532e 05 Acquire timestamped data Start a clocked foreground acquisition data timestamps triggerTime s startForeground Display the results plot timestam
200. ent devices connected to your system using daq getDevices and create a session using the listed Digilent device S daq createSession digilent Generate Analog Output Signals S Data acquisition session using Digilent Inc hardware Will run for 1 second 10000 scans at 10000 scans second No channels have been added Add an analog output channel Add an analog output channel with device ID AD1 and channel ID 1 Set the measurement type to Voltage ch addAnalogOutputChannel s ADi 1 Voltage ch Data acquisition analog output voltage channel 1 on device AD1 TerminalConfig SingleEnded Range 5 0 to 5 0 Volts Name ID 1 Device 1x1 daq di DeviceInfo MeasurementType Voltage Generate a single sample Generate a single scan on demand outVal 2 outputSingleScan s outVal Set session and channel properties Set the generation rate to 300kHz rate 30063 s Rate rate Define the output waveform Generate a 10 Hz sine wave for half a second The length of the output waveform and the specified output rate define the duration of the waveform 16 23 16 Session Based Analog Input and Output 16 24 f 10 duration 0 5 t 1 duration rate rate output sin 2 pi f t Generate continuous data Queue some data and start a clocked foreground generation queueOutputData s output s startForeground Acquire Data and Generate Signals Simultaneously Ac
201. ent 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 Making Quality Measurements 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 Precision and accuracy are illustrated below X x x x x ON X x x Not precise Precise Not accurate Not accurate 32 x Not precise Precise 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
202. entType Range Name 1 dio Devi portO lineO OutputOnly n a 2 dio Devi portO linei OutputOnly n a Add an analog output channel from Dev1 addAnalogOutputChannel s Devi 0 Voltage Output data on both the digital and analog channels outputSingleScan s decimalToBinaryVector 2 1 23 Output Digital Data Serially Using a Software Clock Output Digital Data Serially Using a Software Clock This example shows how to generate signals serially using software clocks and the timer function Create a session and add two digital lines from port 0 on Dev1 to output signals S daq createSession ni addDigitalChannel s Devi PortO LineO 1 OutputOnly You will use Port0 1lineO as the output clock and Port0 line1 as the serial data output Specify serial data to be transferred at 500 bits sec serialData 10 1 10 0 1 1 Configure the software clock using a timer object which has A period of one micro second BusyMode set to queue to accommodate clock stretching and start the timer t timer TimerFcn sendData s serialData Period 0 001 ExecutionMode fixedRate BusyMode queue start t Define the sendData function and output data function sendData obj s serialData s Declare clock and bitNumber as persistent variables persistent clock persistent bitNumber s Persistent variables retain their values in memory between multiple calls to the function Initialize th
203. equest them to develop an interface to the toolbox Refer them to the supported hardware page at www mathworks com products daq supportedio html for a list of currently supported hardware and for information about contacting MathWorks Search for your device on the MathWorks support page at www mathworks com support to see if a solution is listed for using your unsupported device Such solutions are typically available for devices that the next Data Acquisition Toolbox release will support Create the interface yourself To interface unsupported hardware devices to the toolbox use the Data Acquisition Toolbox Adaptor Kit installed with the toolbox For more information about the adaptor kit read the Adaptor Kit User s Guide in the PDF Documentation page for the Data Acquisition Toolbox Hire a consultant to write the interface or a systems integrator to build the system For a potential list of consultants or systems integrators go to the Third Party Products and Services page at www mathworks com connections Consider using hardware that the toolbox already supports 2 11 2 Using Data Acquisition Toolbox Software Accessing Your Hardware 2 12 In this section Connecting to Your Hardware on page 2 12 Acquiring Data on page 2 12 Outputting Data on page 2 13 Reading and Writing Digital Values on page 2 14 Acquire Data in a Loop on page 2 17 Connecting to Your Hardware Perhaps the most e
204. er the previous steps are repeated for each input channel 5 The entire process is repeated for the next sampling instant 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 1 21 T introduction to Data Acquisition e Signal buffer Amplifier A D converter fee ee AS R 4 Input Multiplexer Sample and hold circuit channels Therefore if you 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 Additionally the maximum sampling rate your hardware is rated at typically applies for one c
205. es associated with The hardware channel mapping The channel name The engineering units The display summary for the example given in Acquire Data with a Sound Card on page 6 16 before start is issued is shown below Display Summary of Analog Input AI Object Using AudioPCI Record Acquisition Parameters 8000 samples per second on each channel 8000 samples per trigger on each channel 1 sec of data to be logged per trigger General display Log data to Memory on trigger summary Trigger Parameters 1 Manual trigger s on TRIGGER Engine status Waiting for START 0 samples acquired since starting 0 samples available for GETDATA AI object contains channel s Channel display summary 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 Doing More with Analog Input This chapter presents the complete analog input functionality available to you with Data Acquisition Toolbox software 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 Configure and Sample Input Channels on page 7 2 Manage Acquired Data on page 7 9 Configure Analog Input Triggers on page 7 19 Events and Callbacks on page 7 41 Scaling Dat
206. esented 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 4 17 4 Data Acquisition Workflow 4 18 ai SampleRate 44100 ai samplerate 44100 ai sampler 44100 However when you include property names in a file you should use the full property name This practice can prevent problems with future releases of Data Acquisition Toolbox software if a shortened name is no longer unique because of the addition of new properties Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB 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 value takes precedence over the value defined by the toolbox If a property has a finite set of string values the
207. ev1 Use the daqhwinfo 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 Devi 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 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 10 1 Descriptive Digital O Properties Property Name Description Type Indicate the device object type Name Specify a descriptive name for the device object 10 3 10 Digital Input Output 10 4 You can display the values of these properties for dio with the get function dio Name Type ans nidag1 DIO Digital IO 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 2778 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 b
208. ffective way to get started with Data Acquisition Toolbox software is to connect to your hardware and input or output data 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 example 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 the list of functions If you want detailed information about any properties that are used refer to function properties Note If you are connecting to a CompactDAQ devices or a counter timer device see Counter and Timer Input and Output Acquiring Data If you have a sound card installed you can run the following example which acquires 1 second of data from two analog input hardware channels and then plots the acquired data Accessing Your Hardware Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB You should modi
209. for your operation Step 1 Create a data acquisition session S daq createSession ni S Data acquisition session using National Instruments hardware Will run for 1 second 1000 scans at 1000 scans second No channels have been added Once you create a session object add channels using addAnalogInputChannel addAnalogOutputChannel addCounterInputChannel and addCounterOutputChannel functions Step 2 Configure session properties Change the sessions duration to 10 seconds s DurationInSeconds 10 s Data acquisition session using National Instruments hardware Will run for 10 seconds 10000 scans at 1000 scans second No channels have been added Step 3 Add channels to the session Add an analog input channel to the session s addAnalogInputChannel cDAQiMod1 aid Voltage ans Data acquisition session using National Instruments hardware Will run for 10 seconds 10000 scans at 1000 scans second Number of channels 1 index Type Device Channel MeasurementType Range Name 1 ai cDAQ1Modi aio Voltage Diff 10 to 10 Volts Create a Session Step 4 Change channel properties Examine the channel properties s Channels ans Data acquisition analog input voltage channel aiO on device cDAQ1Mod Coupling DC InputType Differential Range 10 to 10 Volts Name empty ID aiO Device 1x1 daq ni CompactDAQModule MeasurementType Voltage Change the InputType property to Single
210. form and use it with corresponding code 1 scope channel 1 positive to WI through a 1K resistor 1 scope channel 1 negative W2 to GND 20 3 20 Waveform Function Generation This diagram depicts these connections on a breadboard Waveform Generator 1 1kQO Scope Channel 1 Positive Ground Scope Channel 1 Negative Unlike analog input channels the function generation channels control their own waveform frequency If your session contains both function generation channels and any other types of acquisition channels the function generation channels will have their own frequency and all other channels will inherit the sessions frequency If you have analog input channels in the session with function generation channels the analog input channels start first and act as a trigger for function generation channels See Also DutyCycle gain Offset Phase 20 4 Digilent Waveform Function Generation Channels Related Examples Generate a Standard Waveform Using Waveform Function Generation Channels on page 20 9 Generate an Arbitrary Waveform Using Waveform Function Generation Channels on page 20 11 More About Waveform Types on page 20 6 20 5 20 Waveform Function Generation Waveform Types Your hardware can support generation of arbitrary waveforms or standard waveforms or both If your device supports standard waveforms you can set the gain and offset to control the output
211. found with daqhwinfo AO analogoutput winsound 2 Add channels Add one channel to AO chan addchannel A0 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 AO SampleRate 8000 AO TriggerType Manual ActualRate AO SampleRate len ActualRate duration data sin linspace 0 2 pi 500 1en putdata AO0 data 4 Output data Start AO issue a manual trigger and wait for the device object to stop running start AO trigger AO wait AO 5 5 Clean up When you no longer need AO you should remove it from memory and from the MATLAB workspace delete A0 clear AO 8 Analog Output 8 10 Output Data with a National Instruments Board Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB In this example sine wave data is generated in the MATLAB workspace 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 variable You can run this example by typing daqdoc6 2 at the MATLAB Command Window oocQ e RSS 1 Create a device object Create the analog output object AO for a National Instrumen
212. 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 Using Allocated Memory Using Allocated Memory 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 ai SampleRate 11025 ai SamplesPerTrigger 44100 You return the default block size and number of blocks with the Buf feringConfig property ai BufferingConfig ans 1024 30 You return the memory resources with the daqmem function daqmem ai ans winsoundO AI UsedBytes 120 00 KB MaxBytes 763 82 MB The UsedBytes field tells you how much memory is 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 daghwinfo function hwinfo daqghwinfo ai hwinfo NativeDataType ans int16 The value of the NativeDataType field tells you that each sample
213. fy this example to suit your specific application needs 1 Create a device object Create the analog input object ai for a sound card ai analoginput winsound Add channels Add two hardware channels to ai addchannel ai 1 2 Configure property values Configure the sampling rate to 44 1 kHz and collect 1 second of data 44 100 samples for each channel ai SampleRate 44100 ai SamplesPerTrigger 44100 Acquire data Start the acquisition and issue wait to block the MATLAB Command Window until all data is acquired When all the data is acquired wait returns and the data 1s then available to getdata start ai wait ai 2 data getdata ai plot data Clean up When you no longer need ai you should remove it from 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 Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB 2 13 2 Using Data Acquisition Toolbox Software 2 14 You should modify this example to suit your specific application needs 1 Create a device object Create the analog output object ao for a sound card ao analogoutput winsound Add channels Add two hardware channels to
214. g Data Acquisition Toolbox Data Acquisition Toolbox enables you to Configure external hardware devices Read data into MATLAB and Simulink for immediate analysis Send out data You can perform these operations using two different interfaces based on your hardware and the platform The session based interface which works on both Windows 32 bit and 64 bit systems and only works with National Instruments devices including CompactDAQ chassis and Counter Timer modules You cannot use other devices with this interface The legacy interface which works only on Windows 32 bit systems and works with all other supported data acquisition hardware You cannot use CompactDAQ or Counter timer devices with this interface Data Acquisition Toolbox is a collection of functions and a MEX file shared library built on the MATLAB technical computing environment The toolbox also includes several dynamic link libraries DLLs called adaptors which enable you to interface with specific hardware The toolbox provides you with these main features A framework for bringing live measured data into the MATLAB workspace using PC compatible plug in data acquisition hardware 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 Advantech boards that use the Advantech Device Manager 1 3 1 Introducti
215. g signal can be uniquely reconstructed without error from samples taken at equal time intervals 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 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 1 Amplitude 02 f j l l Time sec Sample period Making Quality Measurements In a real world data acquisition environment you might need to condition the signal by filtering out the high frequency components 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 nx 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
216. ground and filter or process the input data simultaneously You can generate data immediately 1n response to the processed input data In this case both the acquisition and generation operations start and stop together You cannot read directly from or write directly to files using the multichannel audio feature Use audioread and audiowrite Multichannel Audio Session Rate The session rate in an audio session is the rate at which the session samples audio data All channels in a session have the same session rate The default session rate for an audio session is 44100 Hz If you have multiple devices in the session make sure that they can all operate at a common session rate For standard sample rates see StandardSampleRates property You can choose a value that is in between the standard values The toolbox will quantize the set rate to the closest standard rate If you choose a rate outside the ranges of the standard rates the session may use it if the device you are using supports it To use non standard rates you must set UseStandardSampleRate to false You cannot set the rate below the standard minimum rate or above the standard maximum rate Multichannel Audio Range Data you acquire or generate using audio channels contains double precision values These values are normalized to 1 to 1 range The session represents data acquired or generated in amplitude without units The audio session s Range property is read only and set at
217. hannel Therefore the maximum sampling rate per channel is given by the formula maximum board rate maximum sampling rate per channel 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 Group Group Group scan 1 scan 2 scann o o o o o o a o o o 1 o o Oo o o o o o k Sample period Channel skew Time 1 22 Analog Input Subsystem 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 1s discussed in the next section Simultaneous Sample and Hold Hardware Simultaneous sample and hold SS H hardware samples all input signals at the 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 sig
218. he channel skew with ChannelSkew If you are acquiring samples using scanning hardware on multiple channels with large loads increased settling time can cause incorrect measurements You can mitigate this issue in one of the following ways Set the ChannelSkewMode to Manual and increase ChannelSkew to a value acceptable by the hardware Set ChannelSkewMode to Equisample The ChannelSkew is automatically calculated based on the number of channels and the sampling rate Manage Acquired Data Manage Acquired Data In this section Analog Input Data Management Properties on page 7 9 Preview Data on page 7 9 Rules for Using peekdata on page 7 10 Poll the Data Block on page 7 11 Extract Data from the Engine on page 7 12 Preview and Extract Data on page 7 14 Return Time Information on page 7 16 Analog Input Data Management Properties 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 digitized data that can be read by the computer 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 as follows Property Name Description SamplesAcquired Indicate the nu
219. he 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 Reference 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 descriptive channel names 6 Getting Started with Analog Input 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 uniq
220. he 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 AO SampleRate 5000 AO RepeatOutput 2 chan UnitsRange 2 2 Queue the data with one call to putdata putdata AO data Calculate the time to wait for data generation to complete The wait time is based on the amount of data queued the number of times the generation repeats extra time to allow for the time it takes to configure and start the device timeToWait length data AO SampleRate AO RepeatOutput 1 1 1 Output data Start AO and wait until all the data is output start AO wait AO timeToWait Clean up When you no longer need AO you should remove it from memory and from the MATLAB workspace delete AO clear AO 8 35 8 Analog Output Start Multiple Device Objects 8 36 With Data Acquisition Toolbox software 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 winsound addchannel ao 1 You should use manual triggers when starting multipl
221. he 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 configuring the channel skew are given below Table 7 1 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 ChannelSkew can only be 0 The values for ChannelSkewMode are given below Table 7 2 ChannelSkewMode Property Values Description ChannelSkewModeValue No channel skew is defined This is the only None valid value for simultaneous sample and hold SS H hardware The channel skew is automatically calculated as Equisample sampling rate number of channels The channel skew must be set with the Manual ChannelSkew property 7 7 7 Doing More with Analog Input 7 8 Description ChannelSkewModeValue The channel skew is given by the smallest value Minimum supported by the hardware If ChannelSkewMode is Minimum or Equisample then ChannelSkew indicates the appropriate read only value If ChannelSkewMode is set to Manual you must specify t
222. hile getdata is blocking This will not stop the acquisition but will return control to MATLAB The SamplesAcquired property keeps a running count of the total number of samples per channel that have been acquired The SamplesAvailable property tells you how many samples you can extract from the engine per channel Preview and Extract 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 Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB You can run this example by typing daqdoc5 2 at the MATLAB Command Window Manage Acquired Data 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 Dev1 AI analoginput mcc 1 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 set up the plot and store the plot handle
223. his data can be retrieved using getdata With some devices the maximum speed of the device changes when it is running in continuous acquisition mode making some speeds unavailable when setting TriggerType to Software Configure Analog Input Triggers Voice Activation Using a Software Trigger This example shows you 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 and a rising slope A portion of the data is then extracted from the engine and plotted Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB You can run this example by typing daqdoc5 3 at the MATLAB Command Window 1 Create a device object Create the analog input object AIVoice for a sound card The installed adaptors and hardware IDs are found with daghwinfo AlVoice analoginput winsound AIVoice analoginput nidaq Dev i AIVoice analoginput mcc 1 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
224. i SampleRate 8000 actualRate ai SampleRate ai SamplesPerTrigger duration ActualRate ai TriggerRepeat 3 ai LogFileName file00 daq ai LoggingMode Disk amp Memory Start the acquisition wait for duration of the acquisition times the number of triggers for the acquisition to complete Then extract all the data stored in the log file as sample time pairs start ai wait ai ai TriggerRepeat 1 duration 1 data time daqread file00 daq Transition Your Code to Session Based Interface Session Based Interface Session based interface does not have a specified file format to log data You can write to a file in binary mode or save data to a MATLAB file 1 Create a session and add 4 analog input channels from Dev1 S daq createSession ni ch addAnalogInputChannel s Dev3 0 3 Voltage Set the same range and terminals for all the channels ch Range 10 0 10 0 ch TerminalConfig SingleEnded Set the sessions rate and duration of acquisition s Rate 50000 s DurationInSeconds 0 01 Start the acquisition and plot the data data timestamps startForeground s figure plot timestamps data Save the acquired data to a MATLAB file fileName data mat save fileName timestamps data Load data from the file into the MATLAB workspace savedData load data mat figure plot savedData timestamps savedData data Set Range of Analog Input Subsystem
225. iable data time startForeground s Plot the data plot time data 16 12 Acquire Analog Input Data i Figure 19 File Edit View Insert Tools Desktop Window Help Asi ERRER EEF ACIE Acquire IEPE Data This example shows how to acquire IEPE data using NI cDAQ 9178 chassis with device NI 9234 on slot 3 with ID cDAQ1Mod3 Create a session and add an analog input channel with IEPE measurement type S daq createSession ni addAnalogInputChannel s cDAQiMod3 0 IEPE Change the channel s ExcitationCurrent to 004 volts s Channels 1 ExcitationCurrent 004 16 13 16 Session Based Analog Input and Output 16 14 Acquire the data against time and save it in a variable data time startForeground s Plot the data plot time data File Edit View Insert Tools Desktop Window Help DNSMS b ARE9RLZ A 08 e0 0 015 0 01 Getting Started Acquiring Data with Digilent Analog Discovery This example shows how to acquire analog input voltage data at a sampling rate of 300kHz The dynamic range of the incoming signal is 2 5 to 2 5 volts You will use the session based interface with the Digilent Analog Discovery hardware Acquire Analog Input Data Create a session with a Digilent device Discover Digilent devices connected to your system using daq getDevices and create a session using the listed Digilent device S daq createSession digil
226. ice object is saved The MAT file has the same name as the 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 Tempi Temp2 time now ai SampleRate 11025 Save and Load Device Objects ai TriggerRepeat 4 ai TriggerFcn Gmycallback time start ai The following command saves ai and the modified property values to the 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 Load the Device Object To load a device object that was saved as a file into the MATLAB workspace type the name of the file at the Command Window For example to load ai from the file myai m ai myai Note that the read only properties such as SamplesAcquired and SamplesAvailable are restored to their default values 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 Gmycallback 7 3071e 005 Save Device Objects to a MAT File Note For analog input objec
227. ice 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 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 SamplesOutputFon 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 The stop function is issued The requested number of samples is output Events and Callbacks Arun 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 1s set to Off Timer Event A timer event is generated whenever the time specified by the TimerPeriod proper
228. ices index Vendor Device ID Description 1 ni Dev1 National Instruments USB 6255 2 ni Dev2 National Instruments USB 6363 Create a session and add two lines from port 0 on Dev1 S daq createSession ni addDigitalChannel s Devi PortO LineO 1 OutputOnly Data acquisition session using National Instruments hardware Clocked operations using startForeground and startBackground are disabled Only on demand operations using inputSingleScan and outputSingleScan can be done Number of channels 2 index Type Device Channel MeasurementType Range Name 1 dio Devi portO lineO OutputOnly n a 2 dio Devi portO linei OutputOnly n a Generate digital data outputSingleScan s 1 0 Generate Signals Using Decimal Data Across Multiple Lines Generate Signals Using Decimal Data Across Multiple Lines This example shows how to convert decimal data and output to two lines on an NI 6255 Find devices connected to your system and find the ID for NI 6255 d daq getDevices d Data acquisition devices index Vendor Device ID Description 1 ni Dev1 National Instruments USB 6255 2 ni Dev2 National Instruments USB 6363 Create a session and add two lines from port 0 on Dev1 S daq createSession ni addDigitalChannel s Devi PortO LineO 1 OutputOnly Data acquisition session using National Instruments hardware Clocked operations using startForeground and startBackground are disabled Only on demand operations using inputSi
229. icolon when Creating a DIO object Adding lines 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 The hardware line mapping Evaluate Digital I O Object Status The line name The port ID The line direction The display summary for the example given in Generate Timer Events on page 10 20 is shown below Display Summary of DigitallO DIO Object Using PCI 6024E Deneraldispl AMET ic x Port Parameters Port 0 is line configurable for reading and writing summary Engine status Engine not required DIO object contains line s Index LineName HwLine Port Direction 1 ni 0 0 In 2 s 1 0 In Line display a ee summary 9 2 2 m 4 AL 3 0 In 5 p 4 0 In
230. if you issue the stop function or an error occurs 6 13 6 Getting Started with Analog Input Acquire Data 6 14 In this section Start Analog Input Object on page 6 14 Log Data on page 6 14 Stop Analog Input Object on page 6 15 Start 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 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 Log 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 d
231. ified number of samples 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 acquisition type you can either fill the display with data or you can acquire a specific number of samples Additionally the specified trigger type determines how the acquisition is initiated Trigger Types The Oscilloscope supports two trigger types which you select from the Type menu 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 Independent Data acquisition 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 E ini xi File Edit
232. igger repeats continuously and you can stop the device object only by issuing the stop function Acquiring Voice Activated and Repeat 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 Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB You can run this example by typing daqdoc5 5 at the MATLAB Command Window 1 Create a device object Create the analog input object AIVoice for a sound card The installed adaptors and hardware IDs are found with daghwinfo AlVoice analoginput winsound AIVoice analoginput nidaq Dev i AIVoice analoginput mcc 1 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 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 trigge
233. iggerCondition property to FallingEdge c s Connections 1 c TriggerCondition FallingEdge Acquire data and store it in dataIn The session waits for the trigger to occur and starts acquiring data when the switch closes datalIn startForeground s Related Examples Multiple Device Synchronization on page 22 7 7 Multiple Chassis Synchronization on page 22 11 More About Synchronization on page 22 2 Clock Connections Clock Connections In this section When to Use Clocks on page 21 5 Import Scan Clock from External Source on page 21 5 Export Scan Clock to External System on page 21 6 When to Use Clocks Use clocks to synchronize operations on all connected devices 1n the session You connect a clock source to a clock destination A clock source can be either external where the clock signal comes from a source outside a session or on a device and terminal pair within a session Destination devices can be external where the signals are received outside the session or devices within the session To understand source and destination devices see Source and Destination Devices on page 22 5 Note You cannot use trigger and clock connections with audio channels Import Scan Clock from External Source To import a scan clock from an external source you must connect the external clock to a terminal and device pair on a device in your session Two circumstances
234. iggerDelayUnits Samples AlVoice TriggerDelay 500 4 Acquire data Start AIVoice acquire the specified number of samples and extract the first 1000 samples from the engine as sample time pairs start AIVoice wait AIVoice durationt1 data time getdata AIVoice 1000 7 27 7 Doing More with Analog Input Plot all the extracted data plot time data xlabel Time sec ylabel Signal Level Volts grid on 5 Clean up When you no longer need AIVoice you should remove it from memory and from the MATLAB workspace delete AIVoice clear AIVoice The output from this example is shown below Note that the pretrigger data constitutes half of the 1000 samples extracted from the engine Additionally 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 Acivaton with Pretiggering 0 3 gib MM E T o Signal Level Volts 0015 001 0005 0 0 005 001 0015 Time sec Repeat 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 7 28 Configure Analog Input Triggers 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 tr
235. ignals are therefore overlapping which shows perfect synchronization 22 10 Multiple Chassis Synchronization Multiple Chassis Synchronization You can synchronize multiple CompactDAQ chassis in a session using one chassis to provide clocking and triggering for all chassis in the session Clock and trigger sources are attached to terminals on the chassis itself All modules on the chassis as well as other connected devices are synchronized using these signals Acquire Synchronized Data Using CompactDAQ Devices This example shows how to acquire voltage data from two devices each on a separate CompactDAQ chassis using a shared trigger and clock to synchronize operations within your session Create a data acquisition session and add channels Add one voltage input channel each from the two NI 9201 devices with IDs cDAQ1Mod1 and cDAQ2Mod1 S daq createSession ni addAnalogInputChannel s cDAQiMod1 0 Voltage addAnalogInputChannel s cDAQ2Mod1 0 Voltage Choose terminal PFIO on cDAQ1 as your trigger source and connect it to terminal PFIO on cDAQ2 Make sure the wiring on the hardware runs between these two terminals addTriggerConnection s cDAQ1 PFIO cDAQ2 PFIO StartTrigger Note that you are using the chassis and terminal pair here not device and terminal pair Choose terminal PFI1 on cDAQ1 as your clock source and connect it to terminal PFI1 on cDAQ2 Make sure the wiring on the ha
236. ile Edit View Help PUE gt Enter search term gt ith A Libraries Library Data Acquisition Toolbox Search Results none Most Frequ lt Simulink Commonly Used Blocks Continuous Discontinuities Discrete Logic and Bit Operations Lookup Tables Math Operations Model Verification Model Wide Utilities Ports amp Subsystems Signal Attributes Signal Routing Sinks Sources User Defined Functions Additional Math amp Discrete H Pa Aerospace Blockset H Pa Communications System Toolbox Computer Vision System Toolbox Pal Control System Toolbox DSP System Toolbox f sition Embedded Coder Fuzzy Logic Toolbox Pa Gauges Blockset HDL Verifier S T ER ET T Analog Input Analog Input Single Sample Analog Output Analog Output Single Sample Digital Input Digital Output 13 5 13 Using the Data Acquisition Blocks in Simulink Build Models to Acquire Data 13 6 In this section Data Acquisition Toolbox Block Library on page 13 6 Bring Analog Data into a Model on page 13 6 Data Acquisition Toolbox Block Library This section provides an example that builds a simple model using the block in conjunction with a block from another block library It illustrates how to bring live analog data into Simulink from a data acquisition device
237. in engine SamplesPerTrigger Configure Analog Input Triggers You can capture posttrigger data using any supported trigger type Acquire Voice Activated Pretriggers Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB 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 Window 1 Create a device object Create the analog input object AIVoice for a sound card The installed adaptors and hardware IDs are found with daghwinfo AlVoice analoginput winsound AIVOice analoginput nidaq Dev1 AIVoice analoginput mcc 1 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 Additionally 500 pretrigger samples are collected duration 2 two second acquisition AlVoice SampleRate 44100 ActualRate AlIVoice SampleRate AlVoice SamplesPerTrigger ActualRate duration AlVoice TriggerChannel chan AlVoice TriggerType Software AlVoice TriggerCondition Rising AlVoice TriggerConditionValue 0 2 AlVoice Tr
238. ing z Value p Valuez p Pretrigger p sec Trigger i D D X 633 80ms Y 76 29uV 10 0ms div On CHO 7 4850V div CH1 5 0Vidiv Display data tips by placing the Click the Trigger button to begin mouse cursor over the trace streaming data into the display 12 5 12 softscope The Data Acquisition Oscilloscope 12 6 The display area contains this information Labels and markers for each trace For this example the traces are labeled CHO and CH1 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 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 display2 Specify a unique display label Add 7 lick the Add button to include Defined scope components the new display in the table Type Label M Channel Channel Scaling m Meas
239. ion Toolbox software 2 Using Data Acquisition Toolbox Software Toolbox Components 2 4 In this section Information and Interaction on page 2 4 MATLAB Functions on page 2 6 Data Acquisition Engine on page 2 6 Hardware Driver Adaptor on page 2 9 Supported Hardware on page 2 9 Unsupported Hardware on page 2 11 Information and Interaction Data Acquisition Toolbox software consists of three distinct components MATLAB functions The data acquisition engine The hardware driver adaptors As shown in the figure these components allow you to pass information between the MATLAB workspace and your data acquisition hardware Toolbox Components MATLAB Interactive functions and data Data Acquisition Toolbox Data isition engi i um Hardware driver adaptors Property values data and events Hardware driver Property values data and events Sensors Hardware DUE I The preceding diagram illustrates how information flows from component to component Information consists of 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 the MATLAB workspace or o
240. ion using National Instruments hardware Will run for 1 second 1000 scans at 1000 scans second Operation starts immediately Number of channels 1 index Type Device Channel InputType Range Name 1 ai cDAQiMod1 aid Diff 10 to 10 Volts For NI devices use either a terminal name like ai2 or a numeric equivalent like 2 for the channel ID Acquire the data and store it in the variable data and plot it data startForeground s plot data Change the number of scans to 4096 s NumberOfScans 4096 s Data acquisition session using National Instruments hardware Will run for 4096 scans 4 096 seconds at 1000 scans second Operation starts immediately Number of channels 1 index Type Device Channel InputType Range Name 1 ai cDAQ1Mod1 ai0 Diff 10 to 10 Volts Changing the number of scans changed the duration of the acquisition to 4 096 seconds at the default rate of 1000 scans per second Acquire the data and store it in the variable data and plot it data startForeground s 16 3 16 Session Based Analog Input and Output 16 4 plot data Acquire Data from Multiple Channels This example shows how to acquire data from multiple channels and from multiple devices on the same chassis In this example you acquire voltage data from an NI 9201 device with ID cDAQ1Mod4 and an NI 9205 device with ID cDAQ1Mod1 Create a session object and add two analog input Voltage channels on cDAQ1Mod1 with channel
241. is addressable for input or 10 7 10 Digital Input Output 10 8 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 Port configurable devices You cannot address the lines associated with a port configurable device individually Therefore you must configure all the lines for either input or output If you attempt to mix the two configurations an error 1s 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 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 Port 0 is line configurable only for E Series devices of the Traditional National Instruments drivers Note that NI DAQmx devices do not support this
242. is stored in the engine 2 Data is extracted from the engine and stored in the MATLAB workspace or output to a disk file These two steps are illustrated below 2 Using Data Acquisition Toolbox Software MATLAB 2 Extract data from the engine Data Acquisition Toolbox Data acquisition engine Acquired data Flow of Output Data Outputting data means that data 1s flowing from the data acquisition engine to the hardware device However before data 1s 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 data sample The flow of output data consists of these two independent steps 1 Data from the MATLAB workspace is queued in the engine 2 Data queued in the engine is output to the hardware These two steps are illustrated below Toolbox Components 1 Queue data into the engine Data Acquisition Toolbox Data acquisition engine Queued data 2 Output data to the hardware Hardware Hardware Driver Adaptor The hardware driver adaptor or 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 dat
243. isition 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 Perform 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 Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB 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 Window 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 daghwinfo AO analogoutput nidaq Dev 2 Add channels Add one hardware channel to AO chan addchannel A0 0 3 Configure property values Create the data to be queued freq 500 w 2 pi freq Scale Data Linearly t linspace 0 2 20000 data 2 sin w t Configure the sampling rate to 5 kHz configure the trigger to repeat two times and scale t
244. jects the diagram would look the same except that lines would be substituted for channels 4 13 4 Data Acquisition Workflow Configure and Return Properties In this section Overview on page 4 14 Property Types on page 4 14 Return Property Names and Property Values on page 4 16 Configure Property Values on page 4 17 Specify Property Names on page 4 17 Default Property Values on page 4 18 Property Inspector on page 4 18 Overview You define and evaluate the behavior of your data acquisition application with device object properties Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB Property Types Data Acquisition Toolbox properties are divided into two main types Common properties Common properties apply to every channel or line contained by a device object 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 Configure and Return Properties Analog Input Object Common properties apply to all channels 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 Common
245. kFreq Set the session to continuous mode sClk IsContinuous true Use Counter Clock To Acquire Clocked Digital Data This example shows how to create a digital input session and import an external clock from the clock session Create a session and add a line from port 0 line 2 on Dev1 S daq createSession ni addDigitalChannel s Devi PortO Line2 InputOnly Tip PFI terminal resources may be shared Check your device routing in NI MAX Set the sessions scan rate to the same as the rate and the frequency of the counter output channel s Rate clockFreq Import the clock from your clock session to synchronize your acquisition Acquire Digital Data Using Counter Channels addClockConnection s External Devi clkTerminal ScanClock Start the counter output channel in the background and ensure it is running startBackground sClk for i 1 10 if sClk IsRunning break else pause 0 1 end end Acquire and plot data datalIn startForeground s plot dataIn Related Examples Acquire Clocked Digital Data with Shared Clock on page 18 9 Acquire Clocked Digital Data with Imported Clock on page 18 7 18 13 18 session Based Digital Operations Acquire Digital Data in Hexadecimal Values 18 14 This example shows how to write data using two channels on an NI 6255 Find devices connected to your system and find the ID for NI 6255 I d daq getDevices d D
246. l 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 ITT x Channel Channel Properties Channel Display Selectthe channels Select both channels Editthe selected channels properties r BufferSize 100000 Color o m Marker o Specify a circular marker symbol MarkerEdgeColor o EE MarkerFaceColor al Markerinterval 4 Specify a marker interval of 4 MarkerSize 6 k Name Mixed k ShowAsScientific al False Showlndicator pa True X Click Help to view property descriptions 12 15 12 softscope The Data Acquisition Oscilloscope Triggering the Oscilloscope 12 16 In this section Acquisition Types on page 12 16 Trigger Types on page 12 16 Configuring Trigger Properties on page 12 17 Acquisition Types 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 pane The Oscilloscope supports three acquisition types which you select from the Acquire menu One Shot Acquire the spec
247. l dedicated hardware is often necessary for performing advanced digital I O operations 1 11 1 Introduction to Data Acquisition 1 12 Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB Counter Timer Subsystems Counter timer C T subsystems are used for event counting frequency and period measurement and pulse train generation Use the session based interface to work with the counter timer subsystems Sensors A sensor converts the physical phenomena of interest into a signal that is input into your 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 anal
248. lds are as follows Event Type Type Field Value Data Field Value Run time error Error AbsTime RelSample 8 27 8 Analog Output 8 28 Event Type Type Field Value Data Field Value String Start Start AbsTime RelSample Stop Stop AbsTime RelSample Trigger Trigger AbsTime RelSample Channel Trigger 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 AbsTime 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 Channel 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 RelSample RelSample is used by all events stored in EventLog to indicate the sample number that was output when the event occurred RelSample is 0 for the start event and for the first Events and Callbacks trigger event regardless of the trigger type Re1Sample is NaN for any event th
249. ller opens with Install from Internet selected At Support package to install select DAQ AUDIO Install Multichannel Audio Device Support 1 Follow the support package installer prompts When prompted log into your MathWorks account Note You need write privileges for the Installation folder At any time during this process you can click Help for more information about downloading support packages 15 5 15 support Package Installer Install National Instruments Device Support 15 6 In this section NIDAQmx Driver Requirements on page 15 6 Install Support Package on page 15 6 Use this process to add support for National Instruments devices After you download and install the drivers you can acquire and generate data using your National Instruments hardware and the session based interface Note You can use this support package only on a host computer running 32 bit or 64 bit Windows that Data Acquisition Toolbox supports NIDAQmx Driver Requirements You must install NIDAQmx driver version 9 1 or newer If you already have the correct version do not install the support package Notes Updating the support package re installs the appropriate NIDAQmx drivers Uninstalling the support package removes only components installed with the support package If you had NIDAQmx drivers before you installed the support package those drivers will not be u
250. log 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 23 for an example of a unipolar signal 1 25 T introduction to Data Acquisition 1 26 10 Volts 5 Volts 0 Volts 5 Volts Unipolar Bipolar Unipolar 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 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 ex
251. ltiple data acquisition boards Application Software Application software provides a convenient front end to the driver software Basic application software allows you to Report relevant information such as the number of samples acquired Data Acquisition System Generate events Manage the data stored in computer memory Condition a signal Plot acquired data With some application software you can also perform analysis on the data MATLAB and Data Acquisition Toolbox software provide you with these capabilities and more 1 19 T introduction to Data Acquisition Analog Input Subsystem 1 20 In this section Function of the Analog Input Subsystem on page 1 20 Sampling on page 1 21 Quantization on page 1 23 Channel Configuration on page 1 27 Transferring Data from Hardware to System Memory on page 1 29 Function of the Analog Input Subsystem Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB Many data acquisition hardware 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 1s digitized you can analyze it store it 1n system memory or store it to a disk file
252. ly Online only Online only Online only Online only Online only Online only Online only Online only Online Only Online only Online only New for Version 1 Revised for Version 2 Release 12 Revised for Version 2 1 Release 12 1 Revised for Version 2 2 Release 13 Revised for Version 2 5 Release 14 Revised for Version 2 5 1 Release 14SP1 Revised for Version 2 6 Release 14SP2 Revised for Version 2 7 Release 14SP3 Version 2 1 Notice updated Revised for Version 2 8 Release 14SP3 Revised for Version 2 8 1 Release 2006a Revised for Version 2 9 Release 2006b Revised for Version 2 10 Release 2007a Minor revision for Version 2 10 Revised for Version 2 11 Release 2007b Revised for Version 2 12 Release 2008a Revised for Version 2 13 Release 2008b Revised for Version 2 14 Release 2009a Revised for Version 2 15 Release 2009b Revised for Version 2 16 Release 2010a Revised for Version 2 17 Release 2010b Revised for Version 2 18 Release 2011a Revised for Version 3 0 Release 2011b Revised for Version 3 1 Release 2012a Revised for Version 3 2 Release 2012b Revised for Version 3 3 Release 2013a Revised for Version 3 4 Release 2013b Revised for Version 3 5 Release 2014a Revised Version 3 6 Release 2014b Revised for Version 3 7 R2015a Revised for Version 3 8 Release 2015b Contents Introduction to Data Acquisition 1 Data Acquisition Toolbox Product Description Key Feat
253. manent 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 Statt Trigger 1 Trigger 2 Trigger n Stop B Data logged to file The properties associated with logging information to a disk file are as follows 11 Saving and Loading 11 6 Property Name Description LogFileName Specify the name of the disk file to which information is logged Logging Indicate if data is being logged 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 created 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 Specify a Filename You specify the name of the log file with the LogFileName property You can specify any value f
254. mber 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 Preview 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 7 9 7 Doing More with Analog Input 7 10 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 After start is issued you can 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 Take a snapshot ofthe most recent requested data LI Data stored i
255. ment Computing InstaCal daghwinfo will return this configuration information For example if you configure your Measurement Computing device for 16 single ended channels using InstaCal daghwinfo 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 Troubleshooting Your Hardware for more information about using vendor tools General Toolbox Information To display general information about the toolbox enter out daqhwinfo 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 enter 2 21 2 Using Data Acquisition Toolbox Software 2 22 out InstalledAdaptors ans mcc nidaq parallel winsound This information tells you that an adaptor 1s available for Measurement Computing and National Instruments devices parallel ports and sound cards Notes The list of installed adaptors might differ for your platform Toolbox adaptors are available to you only if the associated hardware driver is installed Support for the Traditional NI DAQ adaptor will be removed in a future version of the toolbox If you create a Data Acquisition Toolbox M object for Traditional NI DA
256. 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 signal 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 AC power supply then that hum will appear as constant noise level if you are 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 1 37 T introduction to Data Acquisition 1 38 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 An analo
257. n Acquire Synchronized Data Using PXI Devices This example shows how to acquire voltage data from two PXI devices on the same chassis using a shared trigger to synchronize operations within your session PXI devices have a shared reference clock that automatically synchronizes clocking You only need to add trigger connections to synchronize operations in your session with PXI devices Analog input channels on all devices are connected to the same function generator Create a data acquisition session and add channels Add one voltage input channel each from both NI PXI 4461 devices with IDs PXI1S1ot2 and PXI1S1ot3 S daq createSession ni addAnalogInputChannel s PXI1S1ot2 0 Voltage addAnalogInputChannel s PXI1Slot3 O Voltage Add a trigger connection to terminal PXI TrigO on PXI1S10t2 and connect it to terminal PXI TrigO on PX11Slot3 PXI cards are connected through the backplane so you do not have to wire them physically addTriggerConnection s PXI1Sl1ot2 PXI TrigO PXI1S1ot3 PXI TrigO StartTrigger Acquire data and store it in dataIn dataIn startForeground s Plot the data plot dataIn 22 9 22 Session Based Synchronization n Figure 1 File Edit View Insert Tools Desktop Window Help OQdilis hA amp So0oeg4 ag0Bmam 0 100 200 300 400 500 600 700 800 900 1000 All channels are connected to the same function generator and have a shared reference clock The s
258. n on page 22 2 Session Based Synchronization Synchronization on page 22 2 Source and Destination Devices on page 22 5 Automatic Synchronization on page 22 6 Multiple Device Synchronization on page 22 7 Multiple Chassis Synchronization on page 22 11 Synchronize Chassis That Do Not Support Built In Triggers on page 22 12 Synchronize DSA Devices on page 22 13 22 Session Based Synchronization Synchronization 22 2 Use shared triggers and clocks to synchronize data between e Multiple devices Multiple subsystems in a device analog input analog output counter input etc Multiple CompactDAQ or PXI chassis Note Counter output channels run independently and are unaffected by synchronization connections Tip To achieve perfect synchronization you must share both a trigger and a clock between your devices Use addTriggerConnection to add trigger connections and addClockConnection to add a scan clock You can share trigger and clock connections to synchronize operations within a session Synchronization connections can be Devices in a session connected to a trigger or clock source on another device in the session Synchronization Data Acquisition Session Trigger or clock destinations Trigger or clock source Devices and chassis in a session connected to a trigger or clock source on another device in the session 22 3 22 Session Based
259. n Timer TimerFecn TimerPeriod Trigger TriggerFcn Data Missed Event A data missed event is generated immediately after acquired data is missed In most cases data is missed because The engine cannot keep up with the rate of acquisition 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 1s 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 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 han
260. n engine If another peekdata call is issued then once again only the most recent requested samples are returned This situation is illustrated below Time L Take another snapshot of the most recent requested data E Data stored in engine Rules for Using peekdata Using peekdata to preview data follows these rules Manage Acquired Data 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 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 Ifthe 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 Poll 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 Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB
261. n 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 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 Sounds and Audio Devices Properties dialog box Refer to Sound Cards on page A 19 for a picture of this dialog box If you are unsure about the full duplex Legacy Interface Using All Devices 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 website Other Manvfacturers For issues with hardware from any vendor other than Advantech Measurement Computing National Instruments or sound cards go to the supported hardware page and go to the appropriate vendor page for help A 25 A Contacting Math Works Contacting MathWorks A 26 If you need support from MathWorks visit our website at http www mathworks com support Before contacting MathWorks you should run the daqsupport function This function returns diagnostic information such as The versions of MathWorks products you are using Your MATLAB software path The characteristics of your hardware The output from daqsupport is automatically saved to a text file which you can use
262. n the default value is enclosed by curly braces For example the default value for the LoggingMode property is Memory ai LoggingMode Disk Memory Disk amp Memory You can also use the propinfo function or refer to the function properties to find the default value for any property Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB Property Inspector The Property Inspector is a graphical user interface GUI for accessing toolbox object properties The Property Inspector is designed so you can Display the names and current values for object properties Configure and Return Properties Display possible values for enumerated properties Configure the property values Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB You open the Property Inspector with the inspect function or via the Workspace browser by double clicking an object 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 Inspector from the command line inspect ai For more information on the Property Inspector see the inspect reference page 4 19 4 Data Acquisition Workflow Acquire an
263. nal 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 1s no channel skew Group Group Group scan 1 scan 2 scann Channels o 00020200 o 0202020 20 000200200 Sample period Time 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 1 23 T introduction to Data Acquisition 1 24 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 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 Amplitude 0 0 1 02 0 3 0 4 05 06 07 os 0 9 1 Time sec The number of quantized values is given by 2 8 the largest representable value is given by 111 2 2 2 7 0 and the smallest representable value i
264. nalog input channel with a Voltage measurement type addAnalogInputChannel s cDAQiModi ait Voltage 17 5 17 Session Based Counter Input and Output 17 6 Step 4 Acquire the data and store it in the variable data and plot it data startForeground s plot data The plot displays results from both channels in the session object EdgeCount measurement Analog input data Generate Data on a Counter Channel Generate Data on a Counter Channel In this section Use addCounterOutputChannel on page 17 7 Generate Pulses on a Counter Output Channel on page 17 7 Use addCounterOutputChannel Use the addCounterOutputChannel method to add a channel that generates pulses on a counter timer subsystem You can generate on one channel or on multiple channels on the same device using startForeground Generate Pulses on a Counter Output Channel This example shows how to generate pulse data on an NI USB 9402 with device ID eDAQ1Mod65 Step 1 Create a session object and save it to the variable s S daq createSession ni Step 2 Add a counter output channel with a PulseGeneration measurement type ch addCounterOutputChannel s cDAQ1Mod5 0 PulseGeneration ch Data acquisition counter output pulse generation channel ctrO on device cDAQ1Mod5 IdleState Low InitialDelay 2 5e 008 Frequency 100 DutyCycle 0 5 Terminal PFIO Name empty ID ctrO De
265. nd 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 1 27 T introduction to Data Acquisition 1 28 Differential 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 labeled The amplifier has a third connector that allows these signals to be referenced to ground Amplifier Input signal Return signal oH 9 Vo
266. nd Window 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 daghwinf o AI analoginput nidaq Dev 2 Add channels Add one channel to AI chan addchannel AI 0 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 AI SampleRate 10000 ActualRate AI SampleRate AI SamplesPerTrigger duration ActualRate AI TriggerType Manual blocksize AI SamplesPerTrigger Fs ActualRate See The Sampling Rate for more information 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 wait AI duration 1 The wait function pauses MATLAB until either the acquisition completes or the time out elapses whichever comes first If the time out elapses an error occurs Adding 1 second to the duration allows some margin for the time out data getdata AI 6 21 6 Getting Started with Analog Input 6 22 5 Clean up When you no longer need AI you should remove
267. ndor or the operating system sound cards and do not involve using Data Acquisition Toolbox software The sections are as follows A Supported Hardware Supported Hardware For a list of hardware supported by the toolbox go to the Data Acquisition Toolbox product page at MathWorks website www mathworks com products daq supportedio html Hardware and Device Drivers Hardware and Device Drivers In this section Registering the Hardware Driver Adaptor on page A 3 Device Driver Registration on page A 4 Hardware Diagnostics on page A 4 Registering the Hardware Driver Adaptor When you first create a device object the associated hardware driver adaptor is automatically registered The data acquisition engine can now make use of its services The hardware driver adaptors included with the toolbox are all located in the daq private folder These are the full names for each adaptor Supported Vendors Device Types and Full Adaptor Names Vendor Device Type Full Adaptor Name Advantech mwadvantech dll Measurement Computing mwmcc dll National Instruments mwnidaq dll Parallel ports mwparallel dll Windows sound cards mwwinsound dll If for some reason a toolbox adaptor is not automatically registered then register it manually using the daqregister function For example to manually register the sound card adaptor dagregister winsound If you are using a third pa
268. nds ylabel Signal Volts Alternatively you can retrieve data for the second sound card channel by specifying the channel name Log Information to Disk data time daqread file00 daq Samples 1000 2000 Channels Right Retrieve 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 fileO0 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 Retrieve 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 O 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 Retrieve Event Object Channel and Hardware Information You can retrieve event object channel and hardware information by specifying the appropriate arguments to daqread For example to retrieve all event information you must return all the logged
269. ne Function 0 0 0 0 eee ees 10 6 xi Line and Port Characteristics lees 10 7 Reference Individual Hardware Lines 10 11 Write and Read Digital I O Line Values 10 14 Write Digital Values 0 llle 10 14 Read Digital Values llle 10 16 Write and Read Digital Values 10 17 Generate Timer Events llle 10 19 OVERVIEW c ox aer OE DU iq DANN Ica aisi na 10 19 Timer Events 4 S22 auger wi eO e ae fk oe eas aS 10 19 Start and Stop a Digital I O Object 10 20 Generate Timer Events 0 0 00 cece eee 10 20 Evaluate Digital I O Object Status 10 22 Running Property 0 0 cece ee eee 10 22 Display Summary 0 0 00 cece ee eens 10 22 Saving and Loading 11 Save and Load Device Objects 0005 11 2 Save Device Objects toa File llle 11 2 Save Device Objects to a MAT File 11 3 Log Information to Disk 0 00 00 eee 11 5 Analog Input Logging Properties 0000 05 11 5 Specify a Filename 0 0 0 eee eee 11 6 Retrieve Logged Information llle 11 7 Log and Retrieve Information 0000005 11 9 softscope The Data Acquisition Oscilloscope 12 Oscilloscope Overview 0 00 12 2 Opening the Oscilloscope 0 0 000 eee eee 12 2 Hardware Configuration
270. ned 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 daginfo is a structure that stores device object channel and hardware information in two fields Obj Info and HwInfo ObjInfo 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 daghwinfo obj Alternatively you can return only object channel and hardware information with the command daginfo daqread file info Note When you retrieve object information the entire event log is returned to daginfo ObjInfo EventLog regardless of the number of samples retrieved Log Information to Disk Log and Retrieve Information This example illustrates how to log informati
271. nel M CHO Type Pk2Pk Delete Click OK or Apply to add the EN earel a r measurement to the Oscilloscope After you click the OK or Apply button of the Measurement Editor the Measurements pane is automatically added to the Oscilloscope You can then click the Add Measurement button to define additional measurements Making Measurements Oscilloscope ln x File Edit Help Channel Scaling Triggers Measurements Kay eee NE Acquire one Shot Channel CHO E Samples to acquire Type PiaPk x C Fill the display value r48516 Count o Jv Show in Display Vertical Type dependent x Channel CHO Condition Rising x Valuet 33 Channel CHO Y CH1 Offset Scale Type vet Value o 00801 CHO Show in Display c Valuez Pretrigger 0 02 sec CHO 2 57 30V fliv 5 0037ms div On The vertical cursor To add a new measurement to the pane click Add Measurement Trigger 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 define a new measurement type these two ways Ifthe Measurements pane is displayed select New from the Type menu Usethe Measurement Type pane of the Measurement Editor As shown belo
272. ner object that executes your callback function Create an NI session object and add an analog output Voltage channel on cDAQ1Mod2 S daq createSession ni addAnalogOutputChannel s cDAQ1Mod2 ao0 Voltage 16 21 16 Session Based Analog Input and Output 16 22 Specify the channel ID on NI devices using a terminal name like ao1 or a numeric equivalent like 1 Create the data to output and queue the output data queueOutputData s linspace 1 10 1000 Add the listener to the DataRequired event and assign it to the variable Lh lh addlistener s DataRequired queueMoreData Step 4 Create a simple callback function to generate the data and save it as queueMoreData m in your working folder function queueMoreData src event queueOutputData s linspace 1 10 1000 end Generate the signal startBackground s You can execute other MATLAB commands while the generation is in progress In this example issue a pause which causes the MATLAB command line to wait for you to press any key pause Delete the listener delete lh Getting Started Generating Data with Digilent Analog Discovery This example shows how to generate analog output voltage data at a rate of 300kHz The output voltage range of the outgoing signal is 5 0 to 5 0 volts You will use the session based interface with Digilent Analog Discovery hardware Create a session with a Digilent device Discover Digil
273. ng the green line in the Sound Recorder should indicate that data is being captured If this is the case the analog input subsystem on your sound card is functioning properly Note that the CD player converts 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 Run 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 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 i
274. ng two channels on an NI 6255 Find devices connected to your system and find the ID for NI 6255 I d daq getDevices d Data acquisition devices index Vendor Device ID Description 1 ni Dev1 National Instruments USB 6255 2 ni Dev2 National Instruments USB 6363 Create a session and add two lines from port 0 on Dev1 S daq createSession ni addDigitalChannel s Devi PortO LineO 1 InputOnly ans Data acquisition session using National Instruments hardware Clocked operations using startForeground and startBackground are disabled Only on demand operations using inputSingleScan and outputSingleScan can be done Number of channels 2 index Type Device Channel MeasurementType Range Name 1 dio Devi portO lineO InputOnly n a 2 dio Devi portO line1 InputOnly n a Acquire digital data inputSingleScan s ans 18 6 Acquire Clocked Digital Data with Imported Clock Acquire Clocked Digital Data with Imported Clock This example shows how to acquire digital data in the foreground by importing an external scan clock DAQ Session External digital circuit Digital subsystem External Clock You can use a function generator or the on board clock from a digital circuit Here a function generator is physically wired to the terminal PFI9 on device NI 6255 Create a session and add a line from port 0 line 2 on Dev1 S daq createSession ni addDigitalChannel s Devi PortO Line2 InputOnly
275. ngleScan and outputSingleScan can be done Number of channels 2 index Type Device Channel MeasurementType Range Name 1 dio Devi portO lineO OutputOnly n a 2 dio Devi portO linei OutputOnly n a Convert the decimal number 2 to a binary vector and output the result outputSingleScan s decimalToBinaryVector 2 18 21 18 session Based Digital Operations Generate And Acquire Data On Bidirectional Channels 18 22 This example shows how to use a bidirectional channel and read and write data using the same two lines on an NI 6255 Find devices connected to your system and find the ID for NI 6255 d daq getDevices a Data acquisition devices index Vendor Device ID Description 1 ni Dev1 National Instruments USB 6255 2 ni Dev2 National Instruments USB 6363 Create a session and add two lines from port 0 and 2 lines from port 1 on Dev1 S daq createSession ni addDigitalChannel s Devi PortO LineO 1 Bidirectional addDigitalChannel s Dev1 Port1 LineO 1 Bidirectional Data acquisition session using National Instruments hardware Clocked operations using startForeground and startBackground are disabled Only on demand operations using inputSingleScan and outputSingleScan can be done Number of channels 4 index Type Device Channel MeasurementType Range Name 1 dio Dev1 portO lineO Bidirectional Unknown n a 2 dio Devi portO linei Bidirectional Unknown n a 3 dio Devi porti lineO Bidirectional Unknown n
276. nhanced Parallel Port or ECP Extended Capabilities Port The parallel port characteristics for the DIO object parport are shown below hwinfo daqhwinfo parport hwinfo Port 1 ans ID LineIDs Direction Config hwinfo Port 2 ans ID LineIDs Direction Config hwinfo Port 3 ans ID LineIDs Direction Config 0 012 34 5 6 7 in out port 1 01 2 3 4 in port 2 0 1 2 3 in out 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 Add Lines to Digital I O Objects For easy reference the LineName property is automatically populated with a name that includes the port pin number For example dio digitalio parallel 1 Display Summary of DigitallO DIO Obj Using PC Parallel Port Hardware Port Parameters Port O0 is port configurable for reading and writing Port 1 is port configurable for reading Port 2 is port configurable for reading and writing Engine status Engine not required DIO object contains no lines addline dio 0 16 in Index LineName HwLine Port Direction 1 Pin2 0 0 In 2 Pins 1 0 In 3 Pin4 2 0 In 4 Pin5 3 0 In 5 Pin6 4 0 In 6 Pin7 5 0 In 7 Pin8 6 0 In 8 Pin9 7 0 In 9 Pin 5 0 1 In 10 Pi
277. ni3 1 1 In 11 Pini 2 2 1 In 12 Pini0 3 1 In 13 Pin i 4 1 In 14 Pint 0 2 In 15 Pin 4 1 2 In 16 Pin16 2 2 In 17 Pini7 3 2 In Note The Parallel adaptor will be deprecated in a future version of the toolbox If you create a Data Acquisition Toolbox object for parallel in R2008b you will receive a warning stating that this adaptor will be removed in a future release See the supported hardware page at www mathworks com products daq supportedio html for more information Reference 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 10 11 10 Digital Input Output 10 12 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 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 preceding section has the MATLAB indices 1 through 8 automatically assigned to the hardware line
278. nicating with device cDAQ9188 1595393Mod4 reconnect the device in National Instruments Measurement and Automation Explorer and issue daq reset to reset devices settings ADC Overrun Error with External Clock If you see this error when you synchronize acquisition using an external clock ADC Overrun Error If you are using an external clock make sure that the clock frequency matches session rate check your external clock for the presence of noise or glitches check the frequency of your external clock Make sure that it matches the session s rate A 12 Session Based Interface Using National Instruments Devices Cannot Add Clock Connection to PXI Devices When you try to synchronize operations using a PXI 447x series device you see this error DSA device PXI1Slot2 does not support sample clock synchronization Check device s user manual National Instruments DSA devices like the PXI 447x do not support sample clock synchronization You cannot synchronize these devices in the session based interface using addClockConnection Cannot Complete Long Foreground Acquisition When you try to acquire data in the foreground for a long period you may get an out of memory error Switch to background acquisitions and process data as it is received or save the data to a file to mitigate this issue Cannot Use PXI 4461 and 4462 Together You cannot use PXI 4461 and 4462 together for synchronization when PXI 4461 is in the
279. ning 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 Acquire and Output Data Start the Device Object Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB 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 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 Log or Send Data While the device object is running you can Log data acquired
280. ninstalled Install Support Package 1 Open MATLAB 2 Click Add Ons in the MATLAB Home menu 3 Select Get Hardware Support Packages Install National Instruments Device Support up Get Add Ons Manage Add Ons B Package Toolbox B Package App EJ Get Hardware Support Packages Check for Product Updates 1 The Support Package Installer opens with Install from Internet selected At Support package to install select NI DAQmx 15 Support Package Installer 1 Follow the support package installer prompts When prompted log into your MathWorks account Note You need write privileges for the Installation folder At any time during this process you can click Help for more information about downloading support packages 15 8 Session Based Analog Input and Output Acquire Analog Input Data on page 16 2 Generate Analog Output Signals on page 16 18 Acquire Data and Generate Signals Simultaneously on page 16 25 16 Session Based Analog Input and Output Acquire Analog Input Data 16 2 In this section Using addAnalogInputChannel on page 16 2 Acquire Data in the Foreground on page 16 2 Acquire Data from Multiple Channels on page 16 4 Acquire Data in the Background on page 16 5 Acquire Data from an Accelerometer on page 16 6 Acquire Bridge Measurements on page 16 9 Acquire Sound Pressure Dat
281. nnel 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 Stop the Device Object An analog input AT or analog output AO object can stop under one of these conditions Youissue the stop function The requested number of samples is acquired AI or sent AO Arun time hardware error occurs A time out occurs Acquire and Output Data When the device object stops the Running Logging and Sending 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 23 4 Data Acquisition Workflow Clean Up 4 24 When you no longer need a device object you should clean up the MATLAB workspace by removing the object from memory the engine and from the workspace These are the steps you take to end a data acquisition workflow 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
282. nput object and the PXI_CLK10 backplane clock for the ExternalSampleClock property are unavailable You can use PXI STAR in the session based interface with addTriggerConnection and addClockConnection functions All supported PXI modules automatically use the reference Clock PXI_CLK10 Objects created for National Instruments devices and used with the NI DAQmx adaptor have the following behavior when you use the getsample putsample getvalue putvalue functions in the legacy interface and inputSingleScan ouputSingleScan functions in the session based interface The first time the command is used with the object the corresponding subsystem of the device 1s reserved by the MATLAB session Ifyou then try to access that subsystem in a different session of the MATLAB software or any other application from the same computer you may receive an error message informing you that the subsystem is reserved In the session based interface use release to unreserve the subsystem In the legacy interface delete the object in the first session of MATLAB before you can use it in the next one You cannot acquire and generate synchronous data using myDAQ devices because they do not share a hardware clock If you have both input and output channel s in National Instruments Hardware a session and you start the session you will see near simultaneous acquisition and generation See Automatic Synchronization on page 22 6 for more information
283. nsitivity 0 00922 ExcitationCurrent 0 001 ExcitationSource None Coupling DC TerminalConfig Differential Range 5 0 to 5 0 Volts Name ID aiO Device 1x1 daq ni CompactDAQModule MeasurementType Accelerometer Start Acquisition and Plot the Data Use startForeground to acquire and plot the data data time s startForeground plot time data xlabel Time Secs Acquire Analog Input Data Acceleration Gravities ylabel Acceleration Gravities i D Q3 5 0 5 10 15 20 25 30 Time Secs Acquire Bridge Measurements This example shows how to acquire data from an NI USB 9219 device with ID cDAQ1Mod7 and plot the acquired data Create a session object and save it to the variable s S daq createSession ni Add an analog input channel with the Bridge measurement type and save it to the variable ch 16 9 16 Session Based Analog Input and Output 16 10 ch addAnalogInputChannel s cDAQiMod7 aii Bridge You might see this warning Warning The Rate property was reduced to 2 due to the default ADCTimingMode of this device which is HighResolution To increase rate change ADCTimingMode on this channel to HighSpeed To allow a higher acquisition rate change the channel ADCTimingMode to HighSpeed ch ADCTimingMode HighSpeed You might see this warning Warning This property must be the same for all channels on this device
284. ntained by ai You can display the class of chans with the whos command whos chans Name Size Bytes Class Add Channels to an Analog Input Object 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 Reference Individual Hardware Channels on page 6 5 you can also access channels with the Channel property 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 class type and ID 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 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 T
285. nterfacing Handbook A Guide to Analog Signal Conditioning edited by Daniel H Sheingold Analog Devices Inc Norwood MA 1980 2 Bentley John P Principles of Measurement Systems Second Edition Longman Scientific and Technical Harlow Essex UK 1988 3 Bevington Philip R Data Reduction and Error Analysis for the Physical Sciences McGraw Hill New York NY 1969 4 Carr Joseph J Sensors Prompt Publications Indianapolis IN 1997 5 The Measurement Instrumentation and Sensors Handbook edited by John G Webster CRC Press Boca Raton FL 1999 6 PCI MIO E Series User Manual January 1997 Edition Part Number 320945B 01 National Instruments Austin TX 1997 1 42 Using Data Acquisition Toolbox Software This section provides the information you need to get started with Data Acquisition Toolbox software The sections are as follows Installation Information on page 2 2 Toolbox Components on page 2 4 Accessing Your Hardware on page 2 12 Understanding the Toolbox Capabilities on page 2 19 Examine Your Hardware Resources on page 2 21 Getting Help on page 2 25 2 Using Data Acquisition Toolbox Software Installation Information In this section Prerequisites on page 2 2 Toolbox Installation on page 2 2 Hardware and Driver Installation on page 2 3 Prerequisites To acquire live measured data into the MATLAB workspace or to output data from the MA
286. nu The propinfo Function You can use the propinfo function only in the legacy interface to return the characteristics of toolbox properties For example you can find the default value for any 2 25 2 Using Data Acquisition Toolbox Software 2 26 property using this function propinfo returns a structure containing the following fields 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 property default value ReadOnly Indicates when the property is read only Possible values are always never and whileRunning DeviceSpecific If the property is device specific a 1 is returned If a O is returned the property is supported for all device objects of a given type For example to return the characteristics for all the properties associated with the analog input object ai created in the The daqhelp Function section enter Alinfo propinfo ai The characteristics for the TriggerType property are displayed below Alinfo TriggerType ans Type Constraint ConstraintValue DefaultValue ReadOnly DeviceSpecific string enum Manual Immedia
287. o 1 0 4 audo Audio8 4 Audio 1 0 to 1 0 5 audo Audio8 5 Audio 1 0 to 1 0 6 audo Audio8 6 Audio 1 0 to 1 0 19 8 Waveform Function Generation Digilent Analog Discovery Devices on page 20 2 Digilent Waveform Function Generation Channels on page 20 3 Waveform Types on page 20 6 Generate a Standard Waveform Using Waveform Function Generation Channels on page 20 9 Generate an Arbitrary Waveform Using Waveform Function Generation Channels on page 20 11 20 Waveform Function Generation Digilent Analog Discovery Devices 20 2 MATLAB supports the Digilent Analog Discovery design kit a low cost portable USB DAQ device The kit enables project based learning for analog circuit design For professors and course instructors the kit comes with downloadable teaching materials reference designs and lab projects The Data Acquisition Toolbox Support Package for Digilent Analog Discovery hardware lets you perform the following tasks in MATLAB Read data from oscilloscope channels Control and generate data from waveform generators Characterize ICs and measure behavior of the circuit and IC components Configure the sampling rate of the Analog Discovery device Trigger the start of your data acquisition Find and display Digilent Analog Discovery device settings Use the Support Package Installer to download adaptors and drivers For more information see Install Digilent Device Su
288. o Seconds data logging is delayed by the specified number of seconds Capture 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 7 25 7 Doing More with Analog Input 7 26 property value includes the data captured before and after the trigger occurs Capturing pretrigger data is illustrated below Pretrigger samples Trigger samples Trigger occurs SamplesPerTrigger S 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 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 Capture 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 9 Data stored
289. oduct provides access to analog input devices through an analog input object This chapter shows you how to perform simple analog input tasks using just a few functions and properties After reading this chapter you should be able to use the toolbox to configure your own analog input session The sections are as follows Create an Analog Input Object on page 6 2 Add Channels to an Analog Input Object on page 6 4 Configure Analog Input Properties on page 6 9 Acquire Data on page 6 14 Analog Input Examples on page 6 16 Evaluate Analog Input Object Status on page 6 24 6 Getting Started with Analog Input Create an Analog Input Object Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB 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 Hardware Driver Adaptor on page 2 9 The device ID refers to the number associated with your board when it is installed When using NI DAQm x this is usually a string such as Dev1 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 If you do not s
290. of a digital signal is detected ai analoginput mcc 1 addchannel ai 0 7 ai TriggerType 7 36 HwDigital Configure Analog Input Triggers ai TriggerCondition TrigPosEdge 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 1s between 4 volts and 4 volts ai analoginput mcc 1 addchannel ai 0 7 ai TriggerType HwAnalog ai TriggerCondition GateInWindow ai TriggerConditionValue 4 0 4 0 The diagram below illustrates how you connect an 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 Analog Trigger In PCI DAS1602 16 board 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 7 37 7 Doing More with Analog Input The device specific trigger types and trigger conditions are described below and in the properties Analog Input TriggerT
291. of the callback function Specify 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 Use Callback Properties and Functions This section provides examples that show you how to create callback functions and configure callback properties Display 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 Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB You can run this example by typing daqdoc5 6 at the MATLAB Command Window 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 Dev1 AI analoginput mcc 1 7 49 7 Doing More with Analog Input 7 50 2 Add channels Add one hardware channel to AI chan addchannel AI 1
292. og 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 Common Analog Sensors Sensor Physical Variable Accelerometer Acceleration Microphone Pressure Pressure gauge Pressure Resistive temperature device RTD Temperature Strain gauge Force Data Acquisition System Sensor Physical Variable Thermocouple Temperature When choosing the best analog sensor to use you must match the characteristics of the physical variable you are measuring with the characteristics of the sensor The two most important sensor characteristics are The sensor output The sensor bandwidth Note You can use thermocouples and accelerometers without performing linear conversions with the session based interface Sensor Output The output from a sensor can be an analog signal or a digital signal and the output variable 1s 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
293. ogeneous synchronization between PCI and PXI device families AutoSyncDSA property automatically configures all the necessary clocks triggers and sync pulses needed to synchronize DSA devices in your session PXI DSA Devices PXI devices are synchronized using the PXI chassis backplane which includes timing and triggering buses You can automatically synchronize these device series both homogeneously within the same series and heterogeneously across separate series in the same session PXl e 446x series PXYl e 449x series PXI 447x series Hardware Restrictions Before you synchronize ensure that your device combinations adhere to these hardware restrictions 22 13 22 Session Based Synchronization PXI e 446x and 449x Series Chassis restriction You can synchronize these series using either a PXI or a PXIe chassis Make sure all your modules are on the same chassis Slot placement restriction You can use any slot on the chassis that supports your module PXI 447x Series Chassis restriction You can synchronize this series both homogeneously and heterogeneously only on a PXI chassis You can use them on a PXIe chassis to acquire unsynchronized data Slot placement restriction On the PXI chassis only the system timing slot can drive the trigger bus Refer to your device manual to find the system timing slot This image shows the system timing slot on a PXIe 1062Q chassis 22 14 Synchronize DSA Devi
294. on generator to one or more channels using a screw terminal panel If the Advantech Device Test dialog box 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 in the hardware To get support for your Advantech hardware visit their website at http www advantech com Measurement Computing Hardware Driver Version on page A 18 A 17 A Legacy Interface Using All Devices A 18 Hardware Performance on page A 18 Note You can use Measurement Computing hardware only with the legacy interface Driver Version Data Acquisition Toolbox software is compatible only with specific versions of the Universal Library drivers or the associated release of the InstaCal software and is not guaranteed to work with any other versions For a list of the driver versions that are compatible with Data Acquisition Toolbox software refer to the product page on MathWorks website at http www mathworks com products daq supportedio html and click the link for this vendor If you think your driver is incompatible with Data Acquisition Toolbox software then verify that your hardware is functioning properly before updating drivers If your hardware is not functioning properly then you are probably using unsupported drivers Visit the Measurement Computing website at http www measurementcomputing com for the latest driver
295. on to Data Acquisition Measurement Computing Corporation ComputerBoards boards National Instruments CompactDAQ chassis using the session based interface National Instruments boards that use Traditional NI DAQ or NI DAQmx software Note The Traditional NI DAQ adaptor will not be supported in a future version of the toolbox If you create a Data Acquisition Toolbox object for Traditional NI DAQ adaptor beginning in R2008b you will receive a warning stating that this adaptor will be removed in a future release See the supported hardware page at www mathworks com products daq supportedio html for more information Parallel ports LPT1 LPT3 Note The parallel port adaptor will be deprecated in a future version of the toolbox If you create a Data Acquisition Toolbox object for parallel beginning in R2008b you will receive a warning stating that this adaptor will be removed in a future release See the supported hardware page at www mathworks com products daq supportedio html for more information Microsoft Windows sound cards Additionally you can use the Data Acquisition Toolbox Adaptor Kit to interface unsupported hardware devices to the toolbox Event driven acquisitions Exploring the Toolbox A list of the toolbox functions is available to you by typing help daq A list of session based functions is available to you by typing help sessionbasedinterface You can view the code for any function by t
296. on to a disk file and then retrieve the logged information to the MATLAB workspace using various calls to daqread Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB 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 Window 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 Dev1 Sai analoginput mcc 1 Add channels Add two hardware channels to ai ch addchannel ai 1 2 ch addchannel ai 0 1 For NI and MCC 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 ai SampleRate 8000 ActualRate get ai SampleRate ai SamplesPerTrigger duration ActualRate ai TriggerRepeat 3 ai LogFileName file00 daq ai LoggingMode Disk amp Memory Acquire data Start ai wait for ai to stop running and extract all the data stored in the log file as sample time pairs st
297. onal trigger types and trigger conditions are available Refer to the TriggerType and TriggerCondition property reference page for these device specific values Trigger types are grouped into two main categories Device independent triggers 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 device you are using For these 7 21 7 Doing More with Analog Input 7 22 trigger types the callback that initiates the trigger event involves an external analog or digital signal Device specific hardware triggers for National Instruments and Measurement Computing devices are discussed in Device Specific Hardware Triggers on page 7 35 Device independent triggers are discussed below Immediate Trigger If TriggerType is Immediate the default value the trigger occurs immediately after you issue the start function You can configure an analog input object for continuous acquisition by using an immediate trigger and setting SamplesPerTrigger or TriggerRepeat to inf If you use the TriggerRepeat set to inf you must set your TriggerType to Immediate You can u
298. ope Properties pane is shown below Scope Editor x Scope Scope Properties Selectthe scope components display1 P display2 Select Triggers Channel Scaling Editthe selected scope components properties r Name Triggers ShowName PE True Click Help to view property descriptions OK Cancel Help 12 18 Making Measurements Making Measurements In this section Predefined Measurement on page 12 19 Defining a Measurement on page 12 20 Defining a New Measurement Type on page 12 21 Configuring Measurement Properties on page 12 22 Predefined Measurement You can make measurements on the acquired data with the Measurements pane 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 xj Measurement Measurement Properties Measurement Type r Define a new measurement type Type D O O MATLAB function t SOS S S SCS Define a new measurement Cursor type Noe Add Defined measurement types Type MATLAB Function CursorType
299. or 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 Indexed log filenames are identified by a number This number precedes the filename extension and increments by one for successive log files Ifno 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 nyfileO1 dagq 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 Ifthe specified log filename already exists then the existing file is overwritten Log Information to Disk Retrieve 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 Retrieving data and time information Retrieving event device object channel and hardware information Retrieve 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
300. or 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 signals such as temperature This 1s 1n 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 for more information about settling time Excitation Source Some sensors require an excitation source to operate For example strain gauges and resistive temperatur
301. oreground s plot time data Calculate the phase lag between the two channels using the device data sheet NI PXI 4462 data sheet specifies the phase lag to be 63 samples when EnhancedAliasRejectionEnable property is disabled Check to make sure this property is set to false or 0 ch1 EnhancedAliasRejectionEnable Synchronize DSA Devices ans 0 To synchronize signals from these devices the phase lag should be 63 38 or 24 samples Confirm that the data returned is 24 samples apart NI PXI 6672 data sheet specified the phase lag to be 38 samples when EnhancedAliasRejectionEnable property is disabled Check to make sure this property is set to false or 0 ch2 EnhancedAliasRejectionEnable ans 22 19 Transition Your Code to Session Based Interface 23 Transition Your Code to Session Based Interface Transition Your Code to Session Based Interface This topic helps you transition your code from the legacy interface to the session based interface For more information on choosing your interface see Choose the Right Interface on page 3 4 In this section Transition Common Workflow Commands on page 23 2 Acquire Analog Data on page 23 3 Use Triggers on page 23 4 Log Data on page 23 6 Set Range of Analog Input Subsystem on page 23 7 Fire an Event When Number of Scans Exceed Specified Value on page 23 8 Use Timeout to Block MATLAB While an Operation Completes on page 23 9
302. ould a Signal Be Sampled 1 37 Getting Command Line Function Help 1 41 Selected Bibliography 0 0 00 cece nee 1 42 Using Data Acquisition Toolbox Software 2 Installation Information eese 2 2 Pyr r quisites eo XII XE BS ee eA eiae 2 2 Toolbox Installation llle 2 2 Hardware and Driver Installation 2 3 Toolbox Components 00 00 c eee eee 2 4 Information and Interaction 0 0 0 eee eee 2 4 MATLAB Functions 0 0 0 0 eee eee 2 6 Data Acquisition Engine 0 0 cee eee eee 2 6 Hardware Driver Adaptor 00 0 cece eens 2 9 Supported Hardware 0 2 9 Unsupported Hardware 0 0 2 11 Accessing Your Hardware llle 2 12 Connecting to Your Hardware llle 2 12 Acquiring Data i x aeo etr ste bet LI Ee 2 12 Outputting Data iue seed dede vet ertet en 2 13 Reading and Writing Digital Values 2 14 Acquire Data ina Loopa y easa pe Eaa EAE eens 2 17 Understanding the Toolbox Capabilities 2 19 Contents Wile 5 au oa res ecc d e Rd dh s 2 19 Documentation Examples 0 0 0 0 cece eens 2 19 Examples coe 5 sickens atthe ahh be SEP Eae 2 20 Examine Your Hardware Resources 2 21 Using the daqhwinfo Function 0 2 21 General Toolbox Information 0000055
303. out S PDIF audio ports appear in the device list even when you have no devices plugged in Ifyou add this device port to your session and you have no device plugged into the port the operation times out Ifyou have a device plugged into the S PDIF port you may need to match the session rate to the device scan rate to get accurate readings Refer to your device documentation for information Audio Output Channels Display Incorrect ScansOutputByHardware Value If you have downloaded the Windows Audio support package with R2014a you may see incorrect values for the sessions ScansOutputByHardware property The hardware outputs the scans as specified and the property may incorrectly report this number To correct it execute this code S daq createSession directsound scansOutputByHardware incorrect s ScansOutputByHardware correction s NotifyWhenScansQueuedBelow 1 scansOutputByHardware corrected scansOutputByHardware incorrect correction Simultaneous Analog Input and Output Not Synchronized Correctly Do you have an external trigger When you simultaneously acquire and generate analog signals 1n the same session with an external trigger they may correctly synchronize Session Based Interface Using National Instruments Devices MOTU Device Not Working Correctly MOTU devices Ultralight mk3 and Traveler mk3 may not work with DirectSound and Data Acquisition Toolbox versions R2014a and R2014b If you have these
304. owdaqevents events 2 2 Trigger t1 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 Create and Execute Callback Functions When using callback functions you should be aware of these execution rules Callback functions execute in the order in which they are issued Allcallback functions except those associated with timer events are guaranteed to execute Callback function execution might be delayed if the callback involves a CPU intensive task such as updating a figure 7 47 7 Doing More with Analog Input 7 48 Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB You specify the callback function to be executed when a specific event type occurs by including the name of the 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 documentation reference pages Note that if you are executing a local callback function from within a 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 acquir
305. owdaqevents function For example to display a summary of the second event contained by the structure events showdaqevents events 2 2 Trigger 09 53 19 0 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 Use Callback Properties and Callback Functions Examples showing how to create callback functions and configure callback properties are given below Display Number of Samples Output Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB This example illustrates how to generate samples output events You can run this example by typing daqdoc6_4 at the MATLAB Command Window The local callback 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 AO analogoutput nidaq Dev1 AO analogoutput mcc 1 2 Add channels Add two channels to AO chans addchannel A0 1 2 Events and Callbacks chans addchannel A0 0 1 For NI and MCC Configure property values Configure the trigger to repea
306. play 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 can easily configure or return property values for one or more channels As described in Reference Individual Hardware Channels on page 6 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 8 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 To reference individual channels you must specify either MATLAB indices or descriptive channel names Refer to Reference Individual Hardware Channels on page 6 5 for more information Analog Output Properties After hardware channels are added to the analog output object you should configure property values As described in Configure and Return Properties on page 4 14 Data Acquisition Toolbox software supports two basic types of properties for analog output objects common properties and channel properties Common
307. pport on page 15 2 Note Download and install the required drivers before you use the hardware or execute the example For examples on Digilent data acquisition and generation see Getting Started Acquiring Data with Digilent amp Analog Discovery on page 16 14 and Getting Started Generating Data with Digilent amp Analog Discovery on page 16 22 Note You cannot use Digilent Analog Discovery devices with Data Acquisition Toolbox Simulink Blocks Digilent Waveform Function Generation Channels Digilent Waveform Function Generation Channels Waveform function generator channels on a Digilent device can generate both standard and arbitrary waveform functions For more information on waveform types see Waveform Types on page 20 6 This diagram shows you the pin configuration on a typical Digilent Analog Discovery device The yellow and the yellow white lines represent the waveform channels marked by W1 and W2 on the device Trigger In Ground Waveform Generator 1 V Power Supply 5VDC Ground Scope Channel 2 Positive Scope Channel 1 Positive Scope Channel 1 Negative Scope Channel 2 Negative Ground V Power Supply 5VDC Waveform Generator 2 Ground Trigger In 1 2 amp V Wwi1 amp TIO 1 Digital I O Signals e zi LE ee 1 2 amp V W2 4 TO 8 9 10 11 12 13 14 15 ua Digital I O Signals To test the Analog Discovery device create this connection to acquire the generated wave
308. properties and channel line properties are subdivided into these two categories 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 1s shown below 4 15 4 Data Acquisition Workflow 4 16 Base properties Device specific properties Hardware channels lines Base properties Device specific properties Common properties Channel line properties For a complete description of all properties refer to properties Return Property Names and Property Values Once the device object is created you can set the values of all configurable properties Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB The syntax used to return common and channel line properties is describ
309. property is automatically set to On and queued data is output from the engine to the hardware subsystem Sending Off Sending On K o Time Queue data Trigger occurs Output data in engine to hardware Properties associated with analog output triggers are as follows Property Name Description InitialTriggerTime Indicate the absolute time of the first trigger TriggerFcn Specify the callback function to execute when a trigger occurs TriggersExecuted Indicate the number of triggers that execute 8 19 8 Analog Output 8 20 Property Name Description TriggerType 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 8 25 Define 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 8 7 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 Device independent triggers Device specifi
310. ps data xlabel Time seconds ylabel Voltage Volts title Clocked Data Triggered on datestr triggerTime Acquire Analog Input Data Voltage Volts 5 in Clocked Data Triggered on 14 Mar 2013 17 35 06 2 5 005 01 015 02 O25 03 O35 04 045 05 Time seconds 16 17 16 Session Based Analog Input and Output Generate Analog Output Signals 16 18 In this section Use addAnalogOutputChannel on page 16 18 Generate Signals in the Foreground on page 16 18 Generate Signals Using Multiple Channels on page 16 19 Generate Signals in the Background on page 16 20 Generate Signals in the Background Continuously on page 16 21 Getting Started Generating Data with Digilent amp Analog Discovery on page 16 22 Use addAnalogOutputChannel Use the addAnalogOutputChannel method to add a channel that generates analog signals from a National Instruments device including CompactDAQ chassis You can generate data in the foreground or in the background See About the Session Based Interface on page 14 2 for more information Generate Signals in the Foreground This example shows how to generate data using an NI 9263 device with ID cDAQ1Mod2 Create a session object and save it to the variable s S daq createSession ni Change the scan rate of the session object to generate 10 000 scans per second s Rate 10000 s Data acquisition session using N
311. put Workflow Once you create a session use this workflow to set up your digital channels and acquire and generate data daq createsession Add channels addDigitalChannel Queue output dat queueOutputData Add listeners addListner startForeground inputs OutputSingleScan Data processed peration complete delete D Session Based Interface Workflows See Also Functions addDigitalChannel addlistener daq createSession daq getDevices delete inputSingleScan outputSingleScan queueOutputData startBackground startForeground 5 8 Counter and Timer Input and Output Workflow Counter and Timer Input and Output Workflow Once you create a session use this workflow to set up your counter and timer channels and acquire and generate counts ad dCounterInputChannel addCounteroutputChannel Senerate pulses Yes No Acquire counter data OutputSingleScan inputSingleScan See Also Functions addCounterInputChannel addCounterOutputChannel daq createSession daq getDevices inputSingleScan outputSingleScan startBackground startForeground 5 9 D Session Based Interface Workflows Multichannel Audio Input and Output Workflow 5 10 Once you
312. quire Data and Generate Signals Simultaneously This example shows how to acquire data from an NI 9205 device with ID cDAQ1Mod1 and generate signals using an NI 9263 device with ID cDAQ1Mod2 You can acquire data and generate signals at the same time on devices on the same chassis in the session based interface When the session contains output channels duration and number of scans become read only properties of the session The number of scans in a session is determined by the amount of data queued and the duration is s ScansQueued determined by s Rate Step 1 Create an NI session object and add one analog input channel on cDAQ1Mod1 and one analog output channel on cDAQ1Mod2 S daq createSession ni addAnalogInputChannel s cDAQ1iModi aiO Voltage addAnalogOutputChannel s cDAQ1Mod2 ao0 Voltage ans Data acquisition session using National Instruments hardware No data queued Will run at 1000 scans second Number of channels 2 index Type Device Channel MeasurementType Range Name 1 ai cDAQ1iMod1 aid Voltage Diff 10 to 10 Volts 2 ao cDAQ1Mod2 aod Voltage SingleEnd 10 to 10 Volts Queue the output data queueOutputData s linspace 1 10 2500 Display the session object to see the change in duration and the number of scans These values change based on the amount of data queued S s Data acquisition session using National Instruments hardware Will run for 2500 scans 2 5 seconds at 1000 scan
313. r condition is met duration 0 5 One half second acquisition for each trigger AlVoice SampleRate 44100 ActualRate AlIVoice SampleRate AlVoice Timeout 5 AlVoice SamplesPerTrigger ActualRate duration AlVoice TriggerChannel chan AlVoice TriggerType Software 7 29 7 Doing More with Analog Input 7 30 AlVoice TriggerCondition Rising AlVoice TriggerConditionValue 0 2 AlVoice TriggerRepeat 1 Acquire data Start AIVoice 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 wait AIVoice durationt1 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 t1 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 Clean up When you no longer need AIVoice you should remove it from memory and from the MATLAB workspace delete AIVoice clear AIVoice The data acquired for both triggers is shown below Configure Analog Input
314. r first Only one system can reserve this chassis at a time Session Based Interface Using National Instruments Devices What Is a Reserved Hardware Error If you receive the following error The hardware associated with this session is reserved If you are using it in another session use the release function to unreserve the hardware If you are using it in an external program exit that program Then try this operation again Identify the session that is currently not using this device but has reserved it and release the associated hardware resources If the device is reserved by Another session in the current MATLAB program Do one of the following Use release to release the device from the session that is not using the device Delete the session object Another session in a separate MATLAB program Do one of the following Use release to release the device from the session that is not using the device Delete the session object Exit the MATLAB program Another application Exit the other application In none of these measures work reset the device from NI MAX Note Your network device may also appear as unsupported in the device information if it 1s reserved or disconnected What Are Devices with an Asterisk If you get device information and see a device listed with an asterisk next to it then the toolbox does not support this device d daq getDevices dz A 11
315. r instance with a 100 000Hz clock if you request 1 200 samples per second you can set the divider to either 83 or 84 This setting results in a sample rate of either 1 204 82 100 000 83 or 1 190 48 100 000 84 Notes 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 for more information When you change the SampleRate value and the Buf feringMode property is Auto the engine recalculates the Buf feringConfig property value BufferingConfig indicates the memory used by the engine 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 Configure and Sample Input Channels Group Group Group scan 1 scan 2 scan n o o o o o o E o o o v 8 o o d O 9 2 o o o as a a A Sample period Channel skew Time As shown in t
316. r of samples is acquired Arun time hardware error occurs Atime out 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 6 15 6 Getting Started with Analog Input Analog Input Examples 6 16 In this section Basic Steps for Acquiring Data on page 6 16 Acquire Data with a Sound Card on page 6 16 Acquire Data with a National Instruments Board on page 6 20 Basic Steps for Acquiring Data This section illustrates how to perform basic data acquisition tasks using analog input subsystems and Data Acquisition Toolbox software For most data acquisition applications you must follow these basic steps 1 Install and connect the components of your data acquisition 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 To see how to set up continuous analog input acquisitions refer to the Continuous Acquisitions Using Analog Input example Acquire
317. r than the required minimum version of 8 7 Install the NI DAQmx driver of version specified in the error message If you have a version of the NI DAQmx driver already installed update your installation to the minimum required version suggested 1n the error message No vendors found No data acquisition vendors available Reinstall Data Acquisition Toolbox software Corrupted or missing toolbox components Diagnostic Information from vendor NI The required MEX file to communicate with National Instruments hardware is not in the expected location Reinstall Data Acquisition Toolbox software Diagnostic Information from vendor NI The required MEX file to communicate with National Instruments hardware exists but appears to be corrupt Reinstall Data Acquisition Toolbox software Cannot Find Devices If you try to find information using daq getDevices and Do not see the expected device listed For example if you are looking for an NI 9263 and NI 9265 and you type d daq getDevices d Data acquisition devices index Vendor Device ID Description 1 ni cDAQ1Mod1 National Instruments NI 9205 2 ni cDAQ1Mod3 National Instruments NI 9203 3 ni cDAG1Mod4 National Instruments NI 9201 4 ni cDAG1Mod6 National Instruments NI 9213 6 ni cDAQ1Mod8 National Instruments NI 9265 Session Based Interface Using National Instruments Devices A 10 To refresh the toolbox type daqreset If you still do not see the devi
318. rdware runs between these terminals addClockConnection s cDAQ1 PFI1 cDAQ2 PFI1 ScanClock Acquire data and store it in dataIn datalIn startForeground s 22 11 22 Session Based Synchronization Synchronize Chassis That Do Not Support Built In Triggers Certain CompactDAQ chassis like the NI 9174 do not have external BNC PFI connectors and do support built in triggers This example shows how to use the PFI of a digital subsystem on your chassis to synchronize operations This example uses a cDAQ 9174 chassis and synchronizes NI 9104 a digital subsystem with NI 9205 22 12 Synchronize DSA Devices Synchronize DSA Devices In this section PXI DSA Devices on page 22 13 Hardware Restrictions on page 22 13 Synchronize Dynamic Signal Analyzer PXI Devices on page 22 16 PCI DSA Devices on page 22 17 Synchronize DSA PCI Devices on page 22 17 Handle Filter Delays with DSA Devices on page 22 18 The Digital Signal Analyzer DSA product family is designed to make highly accurate audio frequency measurements You can synchronize other PCI and PXI product families using Trigger Connections on page 21 2 and Clock Connections on page 21 5 To synchronize PXI and PCI family of DSA devices you need to use a sample clock with time based synchronization or a reference clock time based synchronization The AutoSyncDSA property allows you to automatically enable both homogeneous and heter
319. re 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 Measurement Computing and National Instruments devices are discussed below and in the properties 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 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 described below and in the properties Analog Input TriggerType and TriggerCondition Values for MCC Hardware 7 35 7 Doing More with Analog Input TriggerType Value TriggerCondition Value Description HwDigital GateHigh The trigger occurs as long as the digital signal 1s high GateLow The trigger occurs as long as the digital signal 1s low TrigHigh The trigger occurs
320. re channel 0 display2 M Hardware CH1 Hardware channel 1 display Click the OK or Apply button to create _ cance aw Hem the reference channel Note that instead of creating the variable ref in the workspace you can specify the expression 3 75 Sin w t in the Expression field Note If the expression returns a complex value only the real part of the value will be displayed 12 9 12 softscope The Data Acquisition Oscilloscope 12 10 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 The channel name Channel names are given by the Name column in the Defined channels table A valid MATLAB expression When the expression is evaluated the channel names are replaced with the associated data that 1s currently being displayed 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 display 1 Channel Editor 1 x Channel Channel Properties Channel Display Define a new channel Mat mood zi Define a math channel named m1 de using the data from CHO and CH1 Expression fabs CHO abs CH1 Display displayt z Display the math channel data with CH1 Add Click the Add bu
321. requires two bytes Therefore the initial allocated memory is 122 880 bytes However if you want to keep all C 5 C Using Allocated Memory the acquired data in memory then 176 400 bytes are required Data Acquisition Toolbox software 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 winsoundO AI UsedBytes 176 00 KB MaxBytes 763 82 MB Note that this was more than enough memory to store all the acquired data Glossary accuracy A determination of how close a measurement comes to the true value acquiring data 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 actuator A device that converts data output from your computer into a physical variable adaptor 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 A D converter An analog input subsystem 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 A
322. rn Property Names and Property Values 4 16 vii viii Contents Configure Property Values 0 00 0 e eee nee 4 17 Specify Property Names 0 000 cece eae 4 17 Default Property Values 0 lees 4 18 Property Inspector e iresten a ena a e eee 4 18 Acquire and Output Data 0 0 00 cee eee 4 20 Device Object States cles 4 20 Start the Device Object llle 4 21 Los or Send Datars sa cox hota Soe Seated Geos US RRR Reeth h 4 21 Stop the Device Object 0 0 0 cece eee 4 22 Clean Up os besitos Oo AG eor EUER eques POU 4 24 Session Based Interface Workflows 5 Session Creation Workflow eeeees 5 2 Analog Input and Output Workflow 5 5 Digital Input and Output Workflow 5 7 Counter and Timer Input and Output Workflow 5 9 Multichannel Audio Input and Output Workflow 5 10 Periodic Waveform Generation Workflow 5 11 Getting Started with Analog Input 6 Create an Analog Input Object 4 6 2 Add Channels to an Analog Input Object 6 4 Channel Group cece ce t 6 4 Reference Individual Hardware Channels 6 5 Add Channels for a Sound Card 00055 6 7 Configure Analog Input Properties 6 9 Analog Input Basic Properties 0000 cc eee 6 9 Sampling Rate zw eet
323. roperty values The screen position You create a softscope file by selecting Save or Save As from the File menu The Save Softscope dialog box is shown below Save in C3 Work amp ex Ee a censusFit m i winsound si File name mee si Save as type All Files Cancel To load a softscope file into the Oscilloscope provide the file name as an argument to the softscope function softscope mcc si 12 27 Using the Data Acquisition Blocks in Simulink Data Acquisition Simulink Blocks Basics on page 13 2 Open the Data Acquisition Block Library on page 13 3 Build Models to Acquire Data on page 13 6 13 Using the Data Acquisition Blocks in Simulink Data Acquisition Simulink Blocks Basics 13 2 This chapter describes how to use the Data Acquisition Toolbox block library The toolbox block library contains six blocks Analog Input Acquire data from multiple analog channels of a data acquisition device Analog Input Single Sample Acquire a single sample from multiple analog channels of data acquisition device Analog Output Output data to multiple analog channels of a data acquisition device Analog Output Single Sample Output a single sample to multiple analog channels of data acquisition device Digital Input Acquire the latest set of values from multiple digital lines of a data acquisition device Digital Output Outpu
324. rophone 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 need to condition an input signal by amplifying it or by removing unwanted frequency Data Acquisition System Components Description components Output signals might need conditioning as well However only input signal conditioning is discussed in this topic 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 The data acquisition components and their relationship to each other are shown below Physical phenomena Data Acquisition System Signal conditioning Acquisition hardware c Computer analysis Physical phenomena The figure depicts the two important features of a data acquisition system Signals are input to a sensor conditioned converted into bits that a computer can
325. rticalOffset data to samplerate Measurements 0 0050 0 2 5730 0 1000x1 double 0 0200 5000 You can export this information to the MATLAB workspace a figure or a MAT file You export measurement data with the Measurement Exporter GUI which you open by selecting the File Export Measurement menu item Measurements data is associated with a defined measurement Note that some measurements such as the horizontal and the vertical cursor have no data to save 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 x Data destination Selectthe measurements to export Channel Mw Type CHO Pk2Pk Variable Name moO v CHO abs m1 Export Close Help Save the measure ment data to the workspace Save the data for both measurements to the variable names mO and m1 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 The hardware configuration The p
326. rty Many devices have additional hardware trigger types which are available to you through the TriggerType property 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 7 35 or the TriggerType reference pages in the properties Note Triggering can be a complicated issue and it has many associated properties For detailed information about triggering refer to Configure Analog Input Triggers on page 1 19 Samples to Acquire per Trigger When a trigger executes a predefined number of samples is acquired for each channel 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 Configure Analog Input Properties ai SamplesPerTrigger 500000 To continually acquire data you set SamplesPerTrigger to inf ai SamplesPerTrigger inf A continuous acquisition stops only
327. rty Specify SampleRate as samples per second For 6 Getting Started with Analog Input 6 10 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 Dev addchannel ai 0 1 ai SampleRate 100000 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 Ifthe rate is within the range of valid values then the engine automatically selects a valid sampling rate Ifthe rate is outside the range of valid values then an error is returned After setting a value for SampleRate find out the actual rate set by the engine ActualRate 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 ai SampleRate ValidRates ConstraintValue ans 1 0e 005 0 0000 2 0000 The maximum rate at which channels are sampled depends on the type of hardware you are using The maximum board rate determines the maximum sampling rate for each channel if you are using simultaneous sample and hold SS H hardware such as a sound card For example suppose you create the analog input obje
328. rty adaptor then you may need to register it manually If so supply the full path name to daqregister For example to register the third party adaptor myadaptor dll daqregister C MATLAB toolbox daq myadaptors myadaptor d1ll A Hardware and Device Drivers Device Driver Registration If you are using a Windows Vista or a Windows 7 system and cannot register device drivers you could have UAC enabled on the system Refer to this technical bulletin for more information Hardware Diagnostics Run daqsupport to get diagnostic information for all installed hardware adaptors on your system Use this information to diagnose issues with your hardware Make sure you include this information when you contact MathWorks support Session Based Interface Using National Instruments Devices Session Based Interface Using National Instruments Devices In this section Session Based Interface and Legacy Interface on page A 5 Is My NI DAQ Driver Supported on page A 6 Why Doesn t My Hardware Work on page A 7 Cannot Create Session on page A 8 Why Was My Session was Deleted on page A 8 Cannot Find Hardware Vendor on page A 8 Cannot Find Devices on page A 9 What Is a Reserved Hardware Error on page A 11 What Are Devices with an Asterisk on page A 11 Network Devices Appears with an Asterisk on page A 12 ADC Overrun Error with External Clock on page A 12 Cannot Add Clock
329. ry information via the Workspace browser by right clicking a toolbox object and selecting Explore Display Summary from the context menu The information displayed reflects many of the basic setup properties described in Analog Output Properties on page 8 4 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 Getting Started with Analog Output Output parameters The sampling rate Trigger parameters The trigger type 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 Channel Summary Information The channel display summary includes property values associated with The hardware channel mapping The channel name The engineering units The display summary shown below is for the example given in Output Data with Sound Card on page 8 8 prior to issuing the start function Display Summary of Analog Output AO Object Using AudioPCI Playback Output Parameters 8000 samples per second on each channel General display Trigger Parameter
330. s To find the version of the driver you are using with Measurement Computing s InstaCal select Start gt Programs gt Measurement Computing gt InstaCal The driver version is available through the Help menu Select Help gt About InstaCal Hardware Performance To troubleshoot your Measurement Computing hardware 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 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 Legacy Interface Using All Devices To get support for your Measurement Computing hardware visit their website at http www measurementcomputing com Sound Cards Test Your Sound Card on page A 19 Microphone and Sound Card Types on page A 22 Test with a Microphone on page A 23 Test with a CD Player on page A 23 Runin Full Duplex Mode on page A 24 Test Your Sound Card Record some data and then play it back to verify that your sound card is functioning When you re
331. s This example shows how to use the function generation channel in a session to generate an arbitrary waveform function at 100kHz frequency The signal s output voltage range is set to 5 0 to 5 0 volts Create a Digilent acquisition session S daq createSession digilent Use daq getdevices to discover available Digilent devices Create a waveform function generation channel with a Arbitrary WaveformType fgenCh addFunctionGeneratorChannel s AD1i 1 Arbitrary fgenCh Data acquisition arbirtray waveform generator 1 on device AD1 Phase O Range 5 0 to 5 0 Volts TerminalConfig SingleEnded Gain 1 Offset O Frequency 4096 WaveformType Sine FrequencyLimit 0 0 25000000 0 Name ID t4 Device 1x1 daq di DeviceInfo MeasurementType Voltage Set the buffer size to 4096 and set the channel to generate a waveform repeatedly from the contents of the buffer The channel outputs for a fixed number of times over the space of the buffer buffersize 4096 len buffersize 1 f0 1 f1 1 f0 ll 20 11 20 Waveform Function Generation 20 12 f3 3 f0 f5 5 f0 waveform sin linspace 0 2 pi f1 len te ga sin linspace 0 2 pi f3 len sin linspace 0 2 pi f5 len waveform 5 waveform max abs waveform waveform end Set the WaveformData of the channel to the waveform fgenCh WaveformData waveform Set the frequency of the channel to 100 KHz
332. s 1 Immediate trigger on START summary Engine status Waiting for START 0 total sec of data currently queued for START 0 samples currently queued by PUTDATA 0 samples sent to output device since START AO object contains channel s Channel display Suy 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 8 13 8 Analog Output AO Channel Manage Output Data Manage Output Data In this section Analog Output Subsystem on page 8 15 Data Queuing on page 8 15 Queue Data with putdata on page 8 17 Analog Output Subsystem 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 8 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
333. s For example the sampling rate of an analog input object applies to all channels contained by 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 3 Channel group hardware channels For digital I O objects the diagram would look the same except that lines would be substituted for channels Hardware Channel IDs to the MATLAB Indices When you add channels to a device object the resulting channel group consists of a mapping between hardware channel IDs and the MATLAB indices 4 11 4 Data Acquisition Workflow 4 12 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 sound cards the channel IDs are one based begin at one However when you reference channels you use the MATLAB indices and not the hardware IDs Given this you should keep in mind that the MATLAB software is one based You can return the vendor s hardware IDs with the daghwinfo function Note You cannot use the legacy interface on 64 bit MATLAB See Abo
334. s a valid sampling rate The rules governing this selection process are described in the SampleRate reference pages Ifthe 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 the device specific properties for more information 8 Analog Output 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 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 Define 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 output object involves specifying the trigger type Trigger types are specified with the TriggerType property The valid TriggerType v
335. s 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 hwlines 2 HwLine n 0 Alternatively you can use the Line property dio Line 1 HwLine dio Line 2 HwLine 1 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 0ut dio Line 1 LineName TrigLine You can now use the line name to reference the line dio TrigLine Direction in Add Lines to Digital I O Objects Add Lines for National Instruments Hardware This example illustrates various ways you can add lines to a DIO object associated with a National Instruments USB 6281 board This board is a multiport device whose characteristics are described in Line and Port Characteristics on page 10 7 Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB To add eight input line
336. s a binary vector and read back the values 10 17 10 Digital Input Output data 13 putvalue dio Line 1 4 data vali getvalue dio bvdata dec2binvec data putvalue dio Line 1 4 bvdata val2 getvalue dio 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 4 Clean up When you no longer need dio you should remove it from memory and from the MATLAB workspace delete dio clear dio 10 18 Generate Timer Events Generate Timer Events In this section Overview on page 10 19 Timer Events on page 10 19 Start and Stop a Digital I O Object on page 10 20 Generate Timer Events on page 10 20 Overview 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 Data Acquisition Toolbox software 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 clocke
337. s are issued a total of 10 seconds of data is output Set the SampleRate AO SampleRate 8000 8 17 8 Analog Output 8 18 Obtain the actual rate set in case hardware limitations prevent using the requested rate ActualRate AO SampleRate Specify one second as the output time Use that to calculate the length of data duration 1 len ActualRate duration Calculate the output signal based on the length of the data data sin linspace 0 2 pi 500 1en All queued data is output once then repeated 4 times for a total of 5 times AO RepeatOutput 4 Queue the output data twice putdata AO data putdata AO data Output data Start AO and wait for the device object to stop running start AO wait A0 11 Clean up When you no longer need AO you should remove it from memory and from the MATLAB workspace delete A0 clear AO Configure Analog Output Triggers Configure Analog Output Triggers In this section Analog Output Trigger Properties on page 8 19 Define Trigger Types on page 8 20 Execute Triggers on page 8 21 How Many Triggers Occurred on page 8 21 When Did the Trigger Occur on page 8 22 Device Specific Hardware Triggers on page 8 23 Analog Output Trigger Properties 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
338. s for Queuing Data Data to be queued in the engine follows these rules Data is output as soon as a trigger occurs An error is returned if a NaN is included in the data stream You can use the native data type of the hardware 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 Scale Data Linearly on page 8 33 for more information about clipping Queve Data with putdata This example illustrates how you can use putdata to queue 16000 samples and then output the data a total of five times using the RepeatOutput property Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB To run this example type daqdoc6 3 at the MATLAB Command Window 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 Dev1 A0 analogoutput mcc 1 Add channels Add one channel to AO chans addchanne1 A0 1 chans addchannel A0 0 For NI and MCC 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 data is repeated four times and two putdata call
339. s for a Sound Card on page 6 7 Channel Group After creating the analog input object you must add hardware channels to it As shown by the figure in Hardware Channels or Lines on page 4 10 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 Hardware Channel IDs to the MATLAB Indices on page 4 11 a channel group consists of a mapping between hardware channel IDs and MATLAB indices see below Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB When adding channels to an analog input object you must follow these rules The channels must reside on the same hardware device You cannot add channels from different devices or from different subsystems on the same device 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 1n the preceding section chans addchannel ai 0 1 The output argument chans is a channel object that reflects the channel array co
340. s 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 Analog Input Subsystem Quantization error bits a 0 1 02 03 04 0 5 0 6 0 7 05 039 1 Time sec 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 gain 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 for more information about how input range gain and precision are related to each other An ana
341. s not running However you should do so only after careful consideration as system performance might be adversely affected which can result in lost data What is Memory Allocation You can manage memory resources using the Buf feringConfig property and the daqmem function With BufferingConfig 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 C How Much Memory Do You Need How Much Memory Do You Need C 4 The memory in bytes required for data storage depends on these factors The number of hardware channels you use The number of samples you need to store in the engine The data type size of each sample The memory required for data storage is given by the formula memory required samples stored x channel 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 datatype The block size and block number are given by the Buf feringConfig 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
342. s second All devices synchronized using cDAQ1 CompactDAQ chassis backplane Details Number of channels 2 index Type Device Channel InputType Range Name 1 ai cDAQiMod1 aid Diff 10 to 10 Volts 2 ao cDAQ1Mod2 ao0 n a 10 to 10 Volts Acquire the data store it in the variable acquiredData 16 25 16 Session Based Analog Input and Output acquiredData startForeground s plot acquiredData 16 26 Session Based Counter Input and Output Analog and Digital Counters on page 17 2 Acquire Counter Input Data on page 17 3 Generate Data on a Counter Channel on page 17 7 17 Session Based Counter Input and Output Analog and Digital Counters 17 2 Use digital and analog counters to count clock ticks and external events Counters output a pulse train or count rising or falling edges and measure many quantities including Frequency Edges PWM Position Pulse generation Counters enable timed acquisition and synchronization Related Examples Acquire Counter Input Data on page 17 3 Generate Data on a Counter Channel on page 17 7 Acquire Counter Input Data Acquire Counter Input Data In this section addCounterInputChannel on page 17 3 Acquire a Single EdgeCount on page 17 3 Acquire a Single Frequency Count on page 17 4 Acquire Counter Input Data in the Foreground on page 17 5 addCounterlnputChannel Use the addCounterInputChannel method
343. s to dio from port 0 addline dio 0 7 in 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 O 1 8 9 in in out out The second way requires two calls to addline and specifies one line ID and multiple port IDs for each call addline dio 0 O 2 in out 3 addline dio 1 O 2 in out 3 The third way requires two calls to addline and specifies multiple line IDs and one port ID for each call addline dio addline dio Lastly you can use four addline calls one for each line added 10 13 10 Digital Input Output Write and Read Digital I O Line Values 10 14 In this section Write Digital Values on page 10 14 Read Digital Values on page 10 16 Write and Read Digital Values on page 10 17 Write Digital Values 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 You write values to digital lines with the putvalue function putvalue requires the DIO object and the values to
344. samples and n is the number of channels dii di din dei doo don dg dao da Extracted data Each column represents a separate input channel dmi dio 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 As shown below if a fraction of the data stored in the engine is extracted then getdata always extracts the oldest data Time gt c Extract the requested data Data stored in engine If another getdata call is issued then once again the oldest samples are extracted 7 13 7 Doing More with Analog Input 7 14 Time A gt a ZA Ll Extract the requested data E Data stored in engine Data extracted from the engine Rules for Using getdata Using getdata to extract data stored in the engine follows these rules Ifthe requested number of samples is greater than the samples to be acquired then an error is returned Ifthe requested data is not returned in the expected amount of time an error is returned The expected time to return data 1s given by the time it takes the engine to fill one data block plus the time specified by the Timeout property You can issue C Ctrl C w
345. se SamplesPerTrigger with any TriggerType setting For more information on trigger repeats see Repeat Triggers on page 7 28 To see how to set up continuous analog input acquisitions refer to the Continuous Acquisitions Using Analog Input example 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 Some acquisition speeds on some devices may not be available when the TriggerType is Software due to hardware limitations When you set TriggerType to Software the device is put into a continuous acquisition mode and acquisition begins when you call start The data collected is analyzed as it comes in to detect the trigger condition you have specified If the data does not contain your trigger condition it is discarded When the trigger condition is met the engine begins storing data T
346. shows how to acquire sound data using NI cDAQ 9178 chassis with device NI 9234 on slot 3 with ID cDAQ1Mod3 Create a session and add an analog input channel with Microphone measurement type S daq createSession ni addAnalogInputChannel s cDAQiMod3 0 Microphone Set the channels sensitivity to0 037 v pa s Channels Sensitivity 0 037 Examine the channel properties s Channels 1 ans Data acquisition analog input microphone channel aiO on device cDAQ1Mod3 16 11 16 Session Based Analog Input and Output Sensitivity 0 037 MaxSoundPressureLevel 136 ExcitationCurrent 0 002 ExcitationSource Internal Coupling AC TerminalConfig PseudoDifferential Range 135 to 135 Pascals Name ID aiO Device 1x1 daq ni CompactDAQModule MeasurementType Microphone ADCTimingMode Change the maximum sound pressure level to 100db and examine channel properties s Channels MaxSoundPressureLevel 100 s Channels 1 ans Data acquisition analog input microphone channel aiO on device cDAQ1Mod3 Sensitivity 0 037 MaxSoundPressureLevel 100 ExcitationCurrent 0 002 ExcitationSource Internal Coupling AC TerminalConfig PseudoDifferential Range 135 to 135 Pascals Name ID aiO Device 1x1 daq ni CompactDAQModule MeasurementType Microphone ADCTimingMode Set acquisition session duration to 4 seconds s DurationInSeconds 4 Acquire the data against time and save it in a var
347. sion Based Interface About the Session Based Interface 14 2 In this section Working with Sessions on page 14 2 Session Based Interface and Data Acquisition Toolbox on page 14 4 Working with Sessions Use the session object to communicate National Instruments devices including a CompactDAQ chassis The general workflow for session operations is as follows About the Session Based Interface Discover supported devices daq getDevices Create DAQ session daq createSession Add channels addAnalogInputChannel addAnalogOutputChannel addDigitalChannel addAudioInputChannel addAudioOutputChannel addCounterInputChannel addCounterOutputChannel Use output channels Queue output data queueOutputData Run MATLAB commands Add listeners addListner Start background Operations startBackground Data processed in background Run other MATLAB commands Stop session Wait for operation to complete Delete listeners delete Operation complete x Start foreground operation startForeground Data processed Operation complete 14 3 14 Using the Session Based Interface 14 4 Use the daq createSession method to create a data acquisitions session See About the Session Based Interface on page 14 2 for more information You can also synchronize operations within the
348. sis Therefore you can configure different engineering unit conversions for each hardware channel 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 the formula includes the appropriate offset 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 1s 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 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
349. site at http WWW ni com Session Based Interface Using National Instruments Devices Cannot Create Session If you try to create a session using daq createSession and you see the following error The vendor ni is not known Use daq getVendors for a list of vendors 1 get vendor information by typing V daq getVendors V Data acquisition vendor National Instruments ID ni FullName National Instruments AdaptorVersion 2 17 R2010b DriverVersion 9 1 NI DAQmx IsOperational true If you do not see output like the one shown see Cannot Find Hardware Vendor on page A 8 Why Was My Session was Deleted This warning A session was deleted while it was running occurs when you start background operations in the session and the session 1s silently deleted This could be caused by the session going out of scope at the end of MATLAB function before the background task completes To avoid this insert a pause after startBackground Cannot Find Hardware Vendor If you try to get vendor information using daq getVendors in the session based interface and receive one of the following errors NI DAQmx driver mismatch Diagnostic Information from vendor NI There was a driver error while Session Based Interface Using National Instruments Devices loading the MEX file to communicate with National Instruments hardware It is possible that the NI DAQmx driver is not installed or is olde
350. sition Toolbox software 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 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 sensor 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 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 the MATLAB workspace The properties associated with engineering units and linearly scaling acquired data are as follows 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 Scaling Data Linearly Note If supported by the hardware you can set the engineering units properties on a per channel ba
351. sociated 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 12 8 Displaying Channels Math channels The data associated with a math channel is calculated in the MATLAB workspace using the data from existing hardware channels math channels 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 Channel menu item For example suppose you want to create a reference waveform to compare to the CHO waveform The first step 1s to create the reference data in the MATLAB workspace t 0 0 0001 0 2 w 200 2 pi ref 3 75 sin w t 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 Channel Properties Channel Display Define a new channel Type Refi e us ae Define a reference channel named r1 using the data from ref Name r1 Expression ref Display MEPA Display the reference data with CHO Add Emm Click the Add button to include Defined channels the new channel in the table mi Type Name Data Source Display M Hardware CH0 Hardwa
352. 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 12 softscope The Data Acquisition Oscilloscope Oscilloscope Overview 12 2 In this section Opening the Oscilloscope on page 12 2 Hardware Configuration on page 12 3 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 pane and a trigger pane Oscilloscope p m ni x File Edit Help Channel Scaling Triggers Horizontal Ten continuous Offset Scale Acquire Continuous Y Samples to acquire Z F Fillthe display C Count oo Vertical CH1 1 H H H H 21 H H 24 H H 2 H H 2 H8 H 4 E Type independent gt a Channel po zl Offset Scale Condition Rising Value Do CHO JJ A m Pretrigder b o SEL EEEEEEEEEEEEEEEEEEEE EF EEE EEE EE EEE EE EEE EEE CHO 1 0V div 10 0msidiv CH1 1 0V div On Trigger Displa
353. sor 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 Amplification Filtering Electrical isolation e Multiplexing Excitation source Amplification Low level 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 1 15 T introduction to Data Acquisition 1 16 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 f
354. ssion Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB Use the daglib Command from the MATLAB Workspace To open the Data Acquisition Toolbox block library enter daqlib Note You cannot use Simulink blocks with 64 bit Windows at the MATLAB Command Window The MATLAB workspace displays the contents of the library in a separate window 13 3 13 Using the Data Acquisition Blocks in Simulink Library daqlib File Edit View Display Diagram Analysis Help Pay tl a Data Acquisition Toolbox A D Data Dsta D A Analog Input Analog Output Single Single Sample apata Date opie DIA Analog Input Analog Output Single Sample Single Sample Digital Digital Input Dala Data Output Digital Input Digital Output Use the Simulink Library Browser To open the Data Acquisition Toolbox block library start the Simulink Library Browser and select the library from the list of available block libraries displayed in the browser To start the Simulink Library Browser enter simulink 13 4 Open the Data Acquisition Block Library at the MATLAB Command window The MATLAB workspace opens the browser window The left pane lists available block libraries with the basic Simulink library listed first followed by other libraries listed in alphabetical order under it To open the Data Acquisition Toolbox block library click its icon al Simulink Library Browser Ioj xl F
355. stems commonly available they are typically multichannel devices offering 12 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 here Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB 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 Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB 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 specia
356. t 100kHz frequency The signal s output voltage range is set to 5 0 to 5 0 volts Create a Digilent acquisition session S daq createSession digilent Use daq getdevices to discover available Digilent devices Create a waveform function generation channel with a Sine WaveformType fgenCh addFunctionGeneratorChannel s AD1 1 Sine fgenCh Data acquisition sine waveform generator 1 on device AD1 Phase O Range 5 0 to 5 0 Volts TerminalConfig SingleEnded Gain 1 Offset O Frequency 4096 WaveformType Sine FrequencyLimit 0 0 25000000 0 Name ID 1 Device 1x1 daq di DeviceInfo MeasurementType Voltage Set the channel s amplitude to 5v using the Gain property and the channel frequency to 100KHz fgenCh Gain 5 fgenCh Frequency fgenCh Data acquisition sine waveform generator 100e3 1 on device AD1 20 9 20 Waveform Function Generation Phase Range TerminalConfig Gain Offset Frequency WaveformType FrequencyLimit Name ID Device MeasurementType 0 5 0 to 5 0 Volts SingleEnded 5 0 100000 Sine 0 0 25000000 0 14 1x1 daq di DeviceInfo Voltage Specify the session to run for 5 seconds and start the generation s DurationInSeconds startForeground s 20 10 5 Generate an Arbitrary Waveform Using Waveform Function Generation Channels Generate an Arbitrary Waveform Using Waveform Function Generation Channel
357. t Status Properties Property Name Description Running Indicate if the device object is running 8 11 8 Analog Output 8 12 Property Name Description 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 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 Window or by excluding the semicolon when Creating an AO object Adding channels Configuring property values using the dot notation You can also display summa
358. t data to multiple digital lines of a data acquisition device Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB You can use these blocks to acquire analog or digital data in a Simulink model or to output analog or digital data from the model to a hardware device You can interconnect these blocks with blocks in other Simulink libraries to create sophisticated models Note You need a license for both Data Acquisition Toolbox and Simulink software to use these blocks Use of Data Acquisition Toolbox blocks requires Simulink a tool for simulating dynamic systems Simulink is a model definition and simulation environment Use Simulink blocks to create a block diagram that represents the computations of your system or application Run the block diagram to see how your system behaves If you are new to Simulink read the Getting Started section of the Simulink documentation to better understand its functionality For more information about the blocks see Data Acquisition Simulink Blocks Basics on page 13 2 Open the Data Acquisition Block Library Open the Data Acquisition Block Library In this section Use the daqlib Command from the MATLAB Workspace on page 13 3 Use the Simulink Library Browser on page 13 4 Note You cannot use the legacy interface on 64 bit MATLAB See About the Se
359. t four times specify daqdoc6_4disp as the callback function to execute whenever 8000 samples are output generate data to be queued and queue the data with one call to putdata AO SampleRate 8000 ActualRate AO SampleRate AO RepeatOutput 4 AO0 SamplesOutputFcnCount 8000 freq AO SamplesOutputFcnCount AO0 SamplesOutputFcn daqdoc6_4disp data sin linspace 0 2 pi 500 3 freq putdata AO data data Output data Start AO The wait function blocks the MATLAB Command Window and waits for AO to stop running start AO wait AO 20 Clean up When you no longer need AO you should remove it from memory and from the MATLAB workspace delete A0 clear AO Display EventLog Information Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB This example illustrates how callback 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 Window 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 A0 analogoutput nidaq
360. tData s outputData Step 5 Generate the data startForeground s Generate Signals in the Background This example shows how to generate signals in the background Create an NI session object and add an analog output Voltage channel to cDAQ1Mod2 Generate Analog Output Signals S daq createSession ni addAnalogOutputChannel s cDAQ1Mod2 ao0 Voltage Specify the channel ID on NI devices using a terminal name like a01 or a numeric equivalent like 1 Create the data to output outputData linspace 1 1 1000 Queue the output data queueOutputData s outputData Generate the signal startBackground s You can execute other MATLAB commands while the generation is in progress In this example issue a pause which causes the MATLAB command line to wait for you to press any key pause Generate Signals in the Background Continuously This example shows how to continuously generate signals A continuous background generation depends on events and listeners to allow your code to enable continuous queuing of data and to react to any errors as they occur For details see Events and Listeners Concepts in the MATLAB Object Oriented Programming documentation In this example you generate from an NI 9263 device with ID cDAQ1Mod2 using a listener on the DataRequired event Listeners execute a callback function when notified that the event has occurred Use Session addlistener to create the liste
361. tSingleScan s ans 71 Acquire a Single Frequency Count This example shows how to acquire a single frequency scan from an NI USB 9402 with device ID cDAQ1Mod5 Step 1 Create an acquisition session S daq createSession ni Step 2 Add a counter channel with a Frequency measurement type addCounterInputChannel cDAQiMod5 ctrO Frequency ans Acquire Counter Input Data 1 ci l cDAQ1Mod5 ctro Frequency n a Step 3 Acquire a single scan s inputSingleScan ans 9 5877e 003 Acquire Counter Input Data in the Foreground This example shows how to acquire rising edge data from an NI USB 9402 with device ID cDAQ1Mod5 and plot the acquired data Step 1 Create an acquisition session s daq createSession ni Step 2 Add a counter channel with an EdgeCount measurement type addCounterInputChannel s cDAQ1Mod5 ctrO EdgeCount ans Data acquisition session using National Instruments hardware Will run for 10 seconds 10000 scans at 1000 scans second Number of channels 1 index Type Device Channel MeasurementType Range Name 1 ci cDAQ1Mod5 ctro EdgeCount n a The counter input channel requires an external clock to perform a foreground acquisition If you do not have an external clock add an analog input channel from a clocked device on the same CompactDAQ chassis to the session This example uses an NI 9205 device on the same chassis with the device ID cDAQ1Mod1 Step 3 Add an a
362. ta are as follows 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 signal and that utilizes the maximum dynamic range of your hardware 8 33 8 Analog Output 8 34 For sound cards you might have to adjust the volume control to obtain the full scale output range of the device See Sound Cards on page A 19 to learn how to access the volume control for your sound card For example suppose OutputRange is 10 10 and UnitsRangeis 5 5 Ifa queued value is 2 5 then the scaled value is 2 5 20 10 or 5 in the appropriate units Note The data acqu
363. te Software Immediate whileRunning 0 This information tells you that The property value data type 1s a string The property value is constrained as an enumerated list of values Getting Help The three possible property values are Manual Immediate and Software The default value is Immediate The property is read only while the device object is running The property is supported for all analog input objects 2 27 Introduction to the Session Based Interface Data Acquisition Session on page 3 2 Choose the Right Interface on page 3 4 Getting Help on page 3 7 3 Introduction to the Session Based Interface Data Acquisition Session The session based interface uses a data acquisition session object that allows you to communicate easily with a National Instruments device or a CompactDAQ chassis You can configure and control one or more National Instruments devices including CompactDAQ chassis using a session object You can create a session using the daq createSession method A session represents one or more channels that you specify on data acquisition devices You configure sessions to acquire or generate data at a specific rate based on the specified number of scans or the duration of the operation The Data Acquisition System section explains how this communication works The relationship between you the application software the driver software the chassis and the devices
364. terface Use the NotifyWhenDataAvailableExceeds property to fire a DataAvailable event 1 Create an acquisition session add an analog input channel Transition Your Code to Session Based Interface S daq createSession ni addAnalogInputChannel s Devi aiO Voltage Set the Rate to 800 000 scans per second which automatically sets the DataAvailable notification to automatically fire 10 times per second s Rate 800000 s NotifyWhenDataAvailableExceeds ans 80000 Increase NotifyWhenDataAvailableExceeds manually to 160 000 s NotifyWhenDataAvailableExceeds 160000 Use Timeout to Block MATLAB While an Operation Completes Legacy Interface 1 Create an analog output object ai for a National Instruments device add a channel and set it to output data at 8000 samples per second with one manual trigger Il ai analogoutput nidaq Dev ch addchannel a0 1 ao SampleRate 8000 ao TriggerType manual ao RepeatOutput 0 putdata ao zeros 10000 1 Start the acquisition and issue a wait command for the acquisition to block MATLAB for two seconds If the acquisition does not complete in two seconds a timeout occurs start a0 wait a0 2 Session Based Interface Background operations run without interrupting the MATLAB command window Use wait to block operations in the MATLAB command window during background operations 1 Create an acquisition session add an analog output channel
365. ternal clock Data Acquisition Toolbox software supports all of these clock sources depending on the requirements of your hardware 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 Analog Input Subsystem Computer Clock The computer PC clock is used for boards that do not possess an onboard clock The computer clock 1s less accurate and has more jitter than the onboard clock and is generally limited to sampling rates below 500 Hz The computer clock is referred to as the software clock 1n 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 Channel Configuration You can configure input channels in one of these two ways Differential 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 grou
366. the Non Plug and Play Drivers item in the list 8 Find the WINIO item near the bottom of the list Double click it and click the Driver tab in the window that appears 9 Expand the Startup Type drop down list and change the entry from Demand to Boot This causes the WINIO driver to start up every time the machine is rebooted 10 Close all the open windows including MATLAB and restart your machine Users with standard or power user privileges can now access the parallel port pins Information for Windows Vista and Windows 7 with UAC Enabled You cannot access the parallel port with User Access Control enabled Run MATLAB as an administrator 1 Right click the MATLAB desktop icon Alternately you can navigate to the MATLAB installation directory and right click on matlab exe 2 Select Run as administrator Note The Parallel adaptor will be deprecated in a future version of the toolbox If you create a Data Acquisition Toolbox object for parallel in R2008b you will receive a warning stating that this adaptor will be removed in a future release See the supported hardware page at www mathworks com products daq supportedio html for more information 10 5 10 Digital Input Output Add Lines to Digital O Objects 10 6 In this section Use the Addline Function on page 10 6 Line and Port Characteristics on page 10 7 Reference Individual Hardware Lines on page 10 11 Use the Addline
367. 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 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 Test with a CD Player To test your sound card with a CD player follow these steps 1 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 23 A Legacy Interface Using All Devices A 24 2 Put an audio CD into your CD player A Windows CD player application should automatically start and begin playing the CD 3 While the CD is playing record audio data by clicking the Record button on the Sound Recorder While recordi
368. therefore there is a certain amount of latency between the actual triggers of the objects In order to reduce this latency you should use manual triggers A manual trigger executes faster than all other trigger types except hardware triggers ai ao TriggerType Manual data zeros 4000 1 putdata ao data start ai ao trigger ai ao Note Device objects cannot be triggered simultaneously unless you use an external hardware trigger The analog output object does not start outputting data until you trigger it The analog input object will start acquiring data when start 1s executed but will discard the data until you trigger it In order to achieve the lowest possible latency you should configure the analog input object s ManualTriggerHwOn property to Trigger Start Analog Input and Output Simultaneously ai ManualTriggerHwOn Trigger data zeros 4000 1 putdata ao data start ai ao trigger ai ao You can determine the time the analog input and analog output objects triggered with the InitialTriggerTime property Calculate the time in seconds between ai and ao aitime ai InitialTriggerTime aotime ao InitialTriggerTime delta abs aotime aitime sprintf d delta 6 ans 2 288818e 005 Note You can also use this feature to simultaneously start any number of analog input and analog output objects 9 Advanced Configurations Using Analog Input and Analog Output Synchronize An
369. they both reference the same device object in the data acquisition engine newai Data Acquisition Engine 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 and should be removed from your workspace using CLEAR You should remove invalid device objects from the workspace with the clear command 4 Data Acquisition Workflow Hardware Channels or Lines 4 10 In this section Add Channels and Lines on page 4 10 Hardware Channel IDs to the MATLAB Indices on page 4 11 Add Channels and 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 obj
370. time step As you can see in the dialog box the acquisition will be asynchronous and the left and right channels will both use the same port since the 1 for all hardware channels option is selected for Number of ports After changing the block size to 5 click OK to close the dialog box For more information on the options and the Analog Input block see the Analog Input block reference page Step 6 Connect the Blocks Connect the output from the Analog Input block to the Scope Use the cursor in the model to drag a connection from the port of the Analog Input block to the scope lolx File Edit View Display Diagram Simulation Analysis Code Tools Help vid c v ES we v 10 0 7 a Analog_input Model Analog Input Model e alansog_ rout Mode 7 winsound 0 Aux Reslte 8000 samples sec Step 7 Run the Simulation Before running the simulation change the run time to 20 seconds by editing the default of 10 seconds in the Simulink editortoolbar 13 11 13 Using the Data Acquisition Blocks in Simulink 13 12 Open the scope by double clicking the Scope block in the model You will see live sound waves in the scope when the model is running Run the simulation by clicking the Run toolbar button During the 20 seconds that the simulation is running speak into the microphone Analog Input Model i ligi xi Fie Edit View Display Diagram Simulation Analysis Code Tools Help
371. tions using getsample and putsample In this case the data 1s acquired and processed as follows Data is acquired through your hardware vendor s software The data is then handed off to the Data Acquisition Toolbox engine The toolbox makes the data available in MATLAB or Simulink The data is run through the control algorithm that you develop in MATLAB or Simulink G6 rt 5 The data is then routed back to the engine through the hardware vendor s software and onto the board This still does not guarantee the response time of a control loop A higher priority thread can take precedence over the control loop Most PC based data acquisition cards provide an internal high accuracy clock that is used to pace data acquisition The cards store the data they collect 1n local memory and then transfer the samples to main computer memory using interrupts or DMA 4 Data Acquisition Workflow 4 4 The timing of samples acquired this way is extremely accurate and these cards can guarantee that the acquired data was obtained at the requested sample rate and that no samples were dropped The maximum sampling rate is governed by the data acquisition card not the PC For true real time closed loop control with MATLAB consider some of these other MathWorks products MATLAB Coder Simulink Desktop Real Time Simulink Real Time Data Acquisition Workflow This example illustrates the basic steps you take during a data acq
372. to help troubleshoot your problem For example to have the MATLAB software generate this file for you type daqsupport Hardware Limitations by Vendor This topic describes limitations of using hardware in the Data Acquisition Toolbox based on limitations places by the hardware vendor B National Instruments Hardware National Instruments Hardware Required hardware drivers and any other device specific software is described in the documentation provided by your hardware vendor For more information see Supported Hardware National Instruments In the legacy interface you should configure the SampleRate property with the setverify function just before starting the hardware Note that the SampleRate value depends on the number of channels added to the device object and the ChannelSkew property value depends on the SampleRate value In the legacy interface only one digital I O DIO object should be associated with a given DIO subsystem To perform separate tasks with the hardware lines you should add all the necessary lines to the DIO object but partition them into separate line groups based on the task You cannot use PXI signals in the legacy interface of Data Acquisition Toolbox software PXI signals are supported by NI 6281 PXI boards and by the Ni DAQmx library but are not available in the legacy interface In particular the ability to use the PXI STAR signal for the HwDigitalTriggerSource property of the analog i
373. tomatically However if for some reason an adaptor is not automatically registered then you must do so manually with the dagregister function Refer to Hardware and Device Drivers on page A 3 for more information You can find out how to create device objects for a particular vendor and subsystem with the ObjectConstructorName field of the daghwinfo function For example to find out Create a Device Object how to create an analog input object for an installed National Instruments board you supply the appropriate Adaptor Specific Information on page 2 22 to daghwinfo out daqhwinfo nidaq out ObjectConstructorName ans analoginput nidaq Devi analogoutput nidaq Devi digitalio nidaq Devi The constructor syntax tells you that you must supply the adaptor name and the hardware ID to the analoginput function ai analoginput nidaq Dev The association between device objects and hardware subsystems is shown below Toolbox device objects Create an Array of Device Objects Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB In the MATLAB workspace you can create an array from existing variables by concatenating those variables together The same is true for device objects For example 4 7 4 Data Acquisition Workflow suppose you create th
374. tor Place the mouse cursor in the display of interest right click and select Edit Properties from the menu 12 7 12 softscope The Data Acquisition Oscilloscope Scope Editor GUI Select Scope from the Edit menu and then choose the Scope Properties 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 The Scope Properties pane and color picker are shown below For descriptions of all display properties click the Help button Scope Editor xi Scope Scope Properties Selectthe scope components Select both displays Triggers Channel Scaling Edit the selected scope components properties Open the color picker and select White from the pop up menv DataTipHitRange 8 i HorizontalOffset 0 0 L Harizontal amp cale 0 01 color 0x HorizontalUnits s 0 9412 1 0 902 Custom Color Layer bottom Black r PixelsPerDivision 30 X ShowAsScientific False k ShowDataTip pee True OK Cancel ShowHorizontalalue PE True Click Help to view property descriptions OK Cancel Help Math and Reference Channels In addition to hardware channels you can display Reference channels The data as
375. ts you can also save acquired data hardware information and so on to a log file Refer to Log Information to Disk on page 11 5 for more information 11 Saving and Loading 11 4 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 myail 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 myail mat load myail Log Information to Disk Log Information to Disk In this section Analog Input Logging Properties on page 11 5 Specify a Filename on page 11 6 Retrieve Logged Information on page 11 7 Log and Retrieve Information on page 11 9 Analog Input Logging Properties While an analog input object is running you can log this information to a disk file Acquired data Event information Device object and channel information Hardware information Logging information to disk provides a per
376. ts board The installed adaptors and hardware IDs are found with daqhwinfo AO analogoutput nidaq Dev 2 Add channels Add one channel to AO chan addchanne1 A0 0 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 AO SampleRate 10000 AO TriggerType Manual ActualRate AO SampleRate len ActualRate duration data sin linspace 0 2 pi 500 1en putdata AO data To see the samples output type Getting Started with Analog Output AO SamplesOutput ans 40000 Output data Start AO issue a manual trigger and wait for the device object to stop running start AO trigger AO wait AO 5 Clean up When you no longer need AO you should remove it from memory and from the MATLAB workspace delete A0 clear AO Evaluate the Analog Output Object Status You can evaluate the status of an analog output AO object by Returning the values of certain properties Invoking the display summary Status Properties The properties associated with the status of your analog output object allow you to evaluate If the device object is running If data is being output from the engine How much data is queued in the engine How much data has been output from the engine These properties are given below Table 8 5 Analog Outpu
377. tton to include Defined channels j the new channel in the table Type Name Data Source Display M Hardware CHO Hardware channel 0 display2 M Hardware CH1 Hardware channel 1 display1 d Reference r1 display2 Click the OK or Apply button to create NN aw Hm the math channel 1 The traces for the hardware math and reference channels are shown below Displaying Channels Oscilloscope E ioj x Channel Scaling Triggers H Horizontal 3 Continuous z Offset Scale Acquire Continuous v Samples to acquire r Fillthe display C Count foo CH1 5 0Vidiv 10 0ms div Vertical mm Type independent x m1 3 7427 Vidiv Channel cho z Condition Rising Valued p Offset Scale Value2 p e Pretigger p sec On CHO 7 4850Vidiv 10 0msidiv r1 7 4850Vidiv Trigger File Edit Help Removing Channel Displays You can remove a channel from a display one of these ways 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 not displayed from the Display column of the table The On Off button of the Channel Scaling pane Refer to Channel Data and Properties on page 12 13 for more information about this pane The Channel pane is shown below with the math and reference channels cleared from the Oscilloscope displays
378. ty 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 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 TriggerFcn Under most circumstances the callback function is not guaranteed to complete execution until sometime after Sending is set to On Record and Retrieve 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 fie
379. u 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 Configure Analog Output Triggers 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 showdaqevents function Device Specific Hardware Triggers 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 1s 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 devices are discussed below and in the properties 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
380. ue 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 O TrigChan addchannel ai 1 15 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 Add Channels to an Analog Input Object ai TrigChan InputRange 10 10 Add Channels for a Sound Card Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB 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
381. ugh some specialized boards support clocked I O Data Acquisition Toolbox software does not support this functionality Accessing Your Hardware Acquire Data in a Loop To make multiple acquisitions using a single analog input object create a single object and execute the acquisition in a loop Delete the object at the end of the loop Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB Create the object outside of the loop ai analoginput nidaq Devi addchannel ai 0 Execute acquisition for ii 1 num_iterations start ai wait ai 2 data getdata ai plot data end Delete the object out of the loop delete ai clear ai If you are creating the object within the loop you must delete the object within the loop as well Execute acquisition for ii 1 num iterations Create the object within the loop ai analoginput nidaq Dev addchannel ai 0 start ai wait ai 2 data getdata ai plot data Delete the object within the loop delete ai end clear ai Note Make sure you delete the object within the loop as it can consume system resources 2 17 2 Using Data Acquisition Toolbox Software For more information about cleaning up the MATLAB workspace refer to Cleaning Up 2 18 Understanding the Toolbox Capobilities Understanding the
382. uisition workflow in the legacy interface using an analog input object You can run this example by typing daqdoc3_1 at the MATLAB Command Window 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 Dev1 AI analoginput mcc 1 2 Add channels Add two channels to AI addchannel AI 1 2 s amp 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 AI SampleRate 11025 AI SamplesPerTrigger 22050 4 Start acquisition Before the start function is issued you might want to begin inputting data from a microphone or a CD player start AI 5 Wait for the acquisition or output to complete Pause MATLAB until either the acquisition completes or 3 seconds have elapsed whichever comes first If 3 seconds elapse an error occurs Understanding the Data Acquisition Workflow wait AI 3 6 Extract the acquired data from the engine and plot results data getdata AI Plot the data and label the figure axes plot data xlabel Samples ylabel Signal Volts 7 Clean up When you no longer need AI you should remove it from memory and from the MATLAB workspace delete AI clear AI To use National Instruments devices like a CompactDAQ chassis or a counter timer de
383. uration GUI by selecting the Edit 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 Iz v Dn m r 12 3 12 softscope The Data Acquisition Oscilloscope added channels with the New Sample Rate GUI which is shown below You open this GUI by selecting the Edit Sample Rate menu item New Sample Rate 1 xi Enter the new sample rate 5000 OK Cancel 12 4 Displaying Channels Displaying Channels In this section Creating a Display on page 12 5 Creating Additional Displays on page 12 6 Configuring Display Properties on page 12 7 Math and Reference Channels on page 12 8 Removing Channel Displays on page 12 11 Creating a Display Click Trigger 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 E 10 n xl Channel Scaling Triggers File Edit Help Horizontal A Continuous gt Offset Scale Acquire Continuous Samples to acquire Z A Fillthe display C Count oo i Vertical VEEEEEEEEEEEEEEEEEEE E FEE EEE FEE E EE EE EE E E EINEN Type independent i CHI Channel CHO z i Offset Scale Condition Ris
384. urement Measurements v Trigger Triggers M Display display1 Delete Click the OK or Apply button to include Came sey Hee 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 Displaying Channels Channel Editor x Channel Channel Properties Channel Display Configure the display for each channel Associate the new display P with CHO Click the OK or Apply button L9 canei E l to update the 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 3 y nix File Edit Help Channel Scaling Triggers Horizontal Acquire continuous x Offset Scale Samples to acquire J 5 Fillthe display C Count roo Vertical T Type independent x CH1 Channel fe HO z Offset Scale Condition Rising x d Valued bo CHO d D Valued p Pretrigger E Sec CHO 7 4850V div 10 0ms div On Trigger CH1 CH1 5 0V div 10 0ms div Configuring Display Properties You can change the display characteristics of the Oscilloscope by configuring display properties You access the display properties these two ways Property Inspec
385. ures X nA dp VERRE UE RU whack PR geet Product Capabilities llle lees Understanding Data Acquisition Toolbox Exploring the Toolbox 0 00 eee Supported Hardware 0 0 cece ee eee Anatomy of a Data Acquisition Experiment System Setup vsu alics Saree ha eal Ae ae ee Calibrati n ail esse mide eie ET Trials Data Acquisition System 0 0000 eee Overview 41 rites ated dus inane Med ir Re edat yos schaun d Data Acquisition Hardware llle eens Sensors 5 46 ied ue ale ad usto rarius oia p a TI Dai qoo odd Signal Conditioning 0 00 cee eee Th Gompu ter eludere week be ta IR Set et eile Is DOL WATLEY a aae eheaend aod ao a Had eR a aan Gb ie BAe e Analog Input Subsystem 0 0000 eee eae Function of the Analog Input Subsystem Sampling xci cam acere ath eR ety aha BUE ORE dus Quantlzation os ek erra et E qam er tem Soke Channel Configuration llle Transferring Data from Hardware to System Memory Making Quality Measurements 05 What Do You Measure 0 llle eee Accuracy and Precision 0 0 0 eee eee Noise 1 2 1 2 1 3 1 3 1 4 1 5 1 6 1 6 1 7 1 8 1 8 1 10 1 12 1 15 1 17 1 17 1 20 1 20 1 21 1 23 1 27 1 29 1 32 1 32 1 32 1 36 vi Contents Matching the Sensor Range and A D Converter Range 1 37 How Fast Sh
386. urs EventLog records a start event trigger event and stop event for each data acquisition session The Data field values are described below AbsTime 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 Channel 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 1 45 7 Doing More with Analog Input 7 46 experienced an overrange signal For the trigger event Channel indicates the index number for each input channel serving as a trigger source OverRange 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 RelSample RelSample 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 Re1Sample is NaN for any event that occurs before the first trigger executes String 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
387. ut However in many cases you simply Understanding the Data Acquisition Workflow want to wait for the acquisition or output to complete before continuing Use the wait function to pause MATLAB until the acquisition is complete 7 Extract your acquired data analog input only After data is acquired you must extract it from the engine with the getdata function 8 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 workflow is used in many of the documentation examples included in this guide Note that the fourth step is treated differently for digital I O objects because they do not store data in the engine Therefore only analog input and analog output objects are discussed in this section Real Time Data Acquisition Because it is operating on a consumer operating system Data Acquisition Toolbox cannot ensure response to an event within a specified maximum time limit In order to ensure a high throughput of the acquisition the toolbox manages acquired data in blocks which increases the latency associated with any given acquired data point In addition it must share system resources with other applications and drivers on the system If you want to create a control loop with the least latency and do not require a deterministic response time you can perform single point opera
388. ut National Instruments recommends that you use differential inputs under any of these conditions The input signal is low level less than 1 volt The leads connecting the signal are greater than 10 feet The input signal requires a separate ground reference point or return signal 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 As shown below the input signal is connected to the positive amplifier socket labeled and the ground is connected to the negative amplifier socket labeled Analog Input Subsystem Amplifier Input signal Ground V out National Instruments suggests that you can use single ended inputs under any of these conditions The input signal is high level greater than 1 volt The leads connecting the signal are less than 10 feet 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 Referenced single ended RSE connection
389. ut accepts the adaptor name and the hardware device ID as input arguments For a list of supported adaptors refer to the Data Acquisition Toolbox Supported Hardware page on the MathWorks Web site The device ID refers to the number associated with your board when it is installed When using NI DAQmx this is usually a string such as Dev1 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 1s 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 nidag Devi 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 Getting Started with Analog Output ao 1x1 1334 analogoutput object Grand total is 53 elements using 1334 bytes 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 8 1 Descriptive Analog Output Properties Property Name Description Name Specify a descriptive name for the device object Type Indicate the device object typ
390. ut the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB 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 Dev To return the hardware IDs supply the device object to daghwinfo and examine the DifferentialIDs 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 The original and modified index assignments are shown below Hardware Channels or Lines Hardware channelID MATLAB index Original index 9 assignment w 8 4X 8 1 Modified index 2 3 Note 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 For digital I O ob
391. utput data from the MATLAB workspace 2 5 2 Using Data Acquisition Toolbox Software to an actuator connected to an analog output subsystem Additionally you can transfer values 1s and 0s between the MATLAB workspace 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 ways you can use events include initiating analysis after a predetermined amount of data is acquired or displaying a message to the MATLAB workspace after an error occurs MATLAB Functions Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB To perform any task with your data acquisition application you must call MATLAB functions from the MATLAB environment Among other things these functions allow you to Create device objects which provide a gateway to your hardware s capabilities and allow you to control the behavior of your application Acquire or output data Configure property values Evaluate your acquisition status and hardware resources Refer to the MATLAB Functions list in the Data Acquisition Toolbox Documentation Center for a list of all toolbox functions You can also display all these functions by typing help daq If you are using a
392. utton 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 p Channel Scaling Horizontal f offset Scale CHI Jeep pene pee Turn this Scale knob until i the displays accommodate i J c i about 50 ms of data Vertical CH1 1 7188Vidiv 5 0037msidiv NER p CH1 E A Offset Scale Turn this Scale knob until the trace amplitudes are maximized in each display r CHO c CHO 2 5730V div 5 0037ms div On 12 13 12 softscope The Data Acquisition Oscilloscope 12 14 To specify a precise horizontal scale or offset you modify 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 Configuring Channel Properties There are two sets of properties associated with the Channel Scaling pane Channel pane properties Properties associated with the controls and labels that make up the pane Channel properties Properties
393. vailable to support multiple channel analog output operations Data Acquisition Toolbox software 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 Output on page 8 2 Manage Output Data on page 8 15 Configure Analog Output Triggers on page 8 19 Events and Callbacks on page 8 25 e Scale Data Linearly on page 8 33 Start Multiple Device Objects on page 8 36 8 Analog Output Getting Started with Analog Output In this section Create an Analog Output Object on page 8 2 Add Channels to an Analog Output Object on page 8 3 Analog Output Properties on page 8 4 Output Data on page 8 7 Analog Output Examples on page 8 8 Evaluate the Analog Output Object Status on page 8 11 Create an Analog Output Object You must create an Analog Output object with which you can use Data Acquisition Toolbox software to perform basic tasks with your analog output AO hardware This section describes the important properties and functions required for an analog output data acquisition session and also provides several device specific examples and ways to evaluate the status of the analog output object You create an analog output object with the analogoutput function analogoutp
394. verter 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 A set of measurements from all input channels in a session at a specific point in time For output channels Glossary 5 Glossary scanning hardware sending sensor session based interface signal conditioning single ended input SS H hardware subsystem Glossary 6 a scan is the values written to all output channels in a session at a specific point in time 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 Data Acquisition Toolbox software 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 session based interface only works with National Instruments CompactDAQ devices including Counter Timer modules You cannot use other devices with this interface Using this interface you create a data acquisition session object with daq createSession You can then add channels to the session and operate all channels within the session together The process of making a sensor signal compatible with the data acquisition hardware Signal con
395. vice 1x1 daq ni CompactDAQModule ADCTimingMode empty Acquire the data and store it in the variable data and plot it data startForeground s plot data Acquire Data in the Background This example shows how to acquire data in the background using events and listeners A background acquisition depends on events and listeners to allow your code to access data as the hardware acquires it and to react to any errors as they occur For more information see Events and Listeners Concepts in the MATLAB Object Oriented Programming documentation Use events to acquire data in the background In this example you acquire data from an NI 9205 device with ID cDAQ1Mod1 using a listener and a DataAvailable event Listeners execute a callback function when notified that the event has occurred Use Session addlistener to create a listener object that executes your callback function Create an NI session object and an analog input Voltage channel on cDAQ1Mod1 S daq createSession ni addAnalogInputChannel s cDAQ1Modi aiO Voltage Add the listener for the DataAvailable event and assign it to the variable lh 16 5 16 Session Based Analog Input and Output 16 6 lh addlistener s DataAvailable plotData For more information on events see Events and Listeners Concepts in the MATLAB Object Oriented Programming documentation Create a simple callback function to plot the acquired data and save it as plotDat
396. vice 1x1 daq ni CompactDAQModule MeasurementType PulseGeneration Step 3 Generate pulses in the foreground s startForeground 17 7 Session Based Digital Operations Digital Subsystem Channels on page 18 2 Acquire Non Clocked Digital Data on page 18 6 Acquire Clocked Digital Data with Imported Clock on page 18 7 Acquire Clocked Digital Data with Shared Clock on page 18 9 Acquire Digital Data Using Counter Channels on page 18 11 Acquire Digital Data in Hexadecimal Values on page 18 14 Control Stepper Motor using Digital Outputs on page 18 15 Generate Non Clocked Digital Data on page 18 20 Generate Signals Using Decimal Data Across Multiple Lines on page 18 21 Generate And Acquire Data On Bidirectional Channels on page 18 22 Generate Signals On Both Analog and Digital Channels on page 18 24 Output Digital Data Serially Using a Software Clock on page 18 25 18 session Bosed Digital Operations Digital Subsystem Channels 18 2 Digital subsystems transfer digital or logical values in bits via digital lines You can perform clocked and non clocked digital operations using the session based interface in the Data Acquisition Toolbox Lines on the digital subsystem are added as channels to your session using addDigitalChannel Digital channels can be InputOnly Allows you to read digital data OutputOnly Allows you to write digital data Bidirectional Allo
397. vice see About the Session Based Interface on page 14 2 4 5 4 Data Acquisition Workflow Create a Device Object In this section Understanding Device Objects on page 4 6 Create an Array of Device Objects on page 4 7 Where Do Device Objects Exist on page 4 8 Understanding Device Objects 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 1s associated with a specific hardware subsystem Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB To create a device object you call functions called object creation functions or object constructors These functions are implemented using the object oriented programming capabilities provided by the MATLAB software which are described in Object Oriented Programming documentation The device object creation functions are listed below 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 au
398. w a new measurement type that calculates the median is defined via the Measurements pane The resulting measurement is the median value of the CHO data 12 21 12 softscope The Data Acquisition Oscilloscope 12 22 Measurements Channel CHO x Type Pk2Pk Value 7 48516 v Show in Display Channel CHO x Type median MATLAB Function mesian Cursor Type None E OK Cancel Type vet 7 value 0 0080 M Show in Display The new measurement type calculates the median value Channel CH0 Se Type Value M Showin Select New from the Type menu Configuring Measurement Properties There are two sets of properties associated with measurements Measurement pane properties Properties associated with the pane label Measurement properties Properties associated with the measurements that are listed in the pane For descriptions of all measurement properties click the Help button of the Scope Properties pane or the Measurement Properties pane Measurement Panel Properties You can change the characteristics of the pane label with the Scope Editor GUI To open this GUI select Scope from the Edit menu choose the Scope Properties pane and select Measurements from the Select the scope components list box The Scope Properties pane 1s shown below Making Measurements x Scope Scope Properties Select the scope components display
399. wing topics Immediate Trigger on page 7 22 Manual Trigger on page 7 22 Software Trigger on page 7 22 Voice Activation Using a Software Trigger on page 7 23 7 20 Configure Analog Input Triggers 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 The analog input TriggerType and TriggerCondition values are given below Table 7 3 Analog Input TriggerType and TriggerCondition Values TriggerType Value TriggerCondition Description 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 leaves the specified range of values Entering The trigger occurs when the signal enters the specified range of values For some devices additi
400. ws you to change the direction of the channel to both read and write data By default the direction is specified as Unknown You can change the direction to Input or Output Note If you are using bidirectional channels you must set the Direction before you use the channel Digital Clocked Operations With clocked operations you can acquire or generate clocked signals at a specified scan rate for a specified duration or number of scans These operations use hardware timing to acquire or generate at specific times The operation is controlled by events tied to subsystem clocks In a clocked acquisition data is transferred from the device to your system memory and displays when the event calls for the data In signal generation data generated from the device is stored in memory until the configured event occurs When an event occurs data is sent via the digital channels to the specified devices Digital systems do not inherently have a clock You can synchronize data by adding a clock in one of these ways Digital Subsystem Channels Perform clocked digital operations Session imports clock for digital operation Digital device has onboard clock Clock available from Import External external source Clock Generate a clock mport to digital from Counter device Output channels Share an analog subsystem clock 18 3 18 session Bosed Digital Operations 18 4 If you have an on board clock on your
401. x Gauges Blockset secs Analog Input Single Sample HDL Verifier Step 3 Add the Analog Input Block to the Model To use the Analog Input block in a model click the block in the library and holding the left mouse button down drag it into the Simulink editor Note how the name on the block changes to reflect the first available analog device connected to your system Step 4 Add a Scope to the Model To illustrate using the block this example creates a simple model that acquires analog data from a microphone via a sound card the analog device and then outputs the data to a scope where you can see the intensity of the sound waves To create this model this example uses a Scope block from the basic Simulink block library Expand the Simulink block library by clicking Simulink at the top of the library list if it is not already open In the library window open the Sinks group From this group click the Scope block in the library and holding the left mouse button down drag the block into the Simulink editor 13 7 13 Using the Data Acquisition Blocks in Simulink amp P Aerospace Blockset Pa Communications System Toolbox Computer Vision System Toolbox Control System Toolbox ISP System Toolbox Data Acquisition Toolbox 13 8 Build Models to Acquire Data Step 5 Specify Block Parameters To specify Analog Input block parameter settings double click
402. xternal clock does not automatically set the rate of your session Manually set the session s rate to match the expected external clock frequency Generate a Clock Using a Counter Output Channel This example shows how to create a clock session with a counter output channel that will continuously generate frequency pulses in the background Use this channel as an external clock in your clocked digital acquisition Create a clock frequency that you will use to synchronize the frequency and rate of your counter output as well as the rate of your digital acquisition in the next step clockFreq 100 Create a session and add a counter output channel with PulseGeneration measurement type sClk daq createSession ni 18 11 18 session Based Digital Operations 18 12 chi addCounterOutputChannel sClk Devi 0 PulseGeneration Tip Make sure the counter channel you add is not being used in a different session You will get a terminal conflict error if the hardware is reserved in another session Save the counter output terminal to a variable You will use this terminal in your digital session to specify the external clock that synchronizes your digital clocked operations clkTerminal chi Terminal You will use this terminal in your digital session to specify the external clock that synchronizes your digital clocked operations Set the frequency of your counter session to the clock frequency chi Frequency cloc
403. y Waveform Using Waveform Function Generation Channels l l eens 20 11 Triggers and Clocks 21 Trigger Connections l l eee 21 2 When to Use Triggers llle 21 2 External Triggering llle 21 3 Acquire Voltage Data Using a Digital Trigger 21 4 Clock Connections lleleeeee eee 21 5 When to Use Clocks llle 21 5 Import Scan Clock from External Source 21 5 Export Scan Clock to External System 21 6 Session Based Synchronization 22 Synchronization llle 22 2 Source and Destination Devices 22 5 Automatic Synchronization llle 22 6 Multiple Device Synchronization 22 7 Acquire Synchronized Data Using USB Devices 22 7 Acquire Synchronized Data Using PXI Devices 22 9 Xvii Multiple Chassis Synchronization 22 11 Acquire Synchronized Data Using CompactDAQ Devices 22 11 Synchronize Chassis That Do Not Support Built In Triggers oill2ervmuawe WI SX YR BE LEE Sew 22 12 Synchronize DSA Devices 0 0 00 eens 22 13 PRT DSA Devices aa peret a a epe ae ee ace ates amp ee ees 22 13 Hardware Restrictions 0 0 0 e eee eee eee 22 13 Synchronize Dynamic Signal Analyzer PXI Devices 22 16 PCI DSA Devices 0 0 0 0 22 17 Synchronize DSA PCI Devices 0 00000 es 2
404. y pane Channel scaling pane Trigger pane Note that you can also open the Oscilloscope by Oscilloscope Overview Typing softscope without any arguments and using the Hardware Configuration GUI to configure the hardware device Supplying a configuration file as an input argument to softscope Refer to Saving and Loading the Oscilloscope Configuration on page 12 27 for more information 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 ioi xl Adaptor ncc x ID fo Set the sampling rate Sample Rate Ha 5000 C lo 5000 kz Input Type Differential x Select the channels to add Select All Unselect All HW Channel Name Description Input Range CHO Hardware channel 0 2 z Display only the first CH1 Hardware channel 1 T two channels CH2 Hardware channel 2 Ir CH3 Hardware channel 3 CH4 Hardware channel 4 CH5 Hardware channel 5 CHE Hardware channel 6 CH7 Hardware channel 7 Click the OK button to open xoc penses ees i Oscilloscope You can also open the Hardware Config
405. y vector is required If you do not specify the number of bits then the minimum number of bits needed to represent the decimal value 1s used Alternatively you can create the binary vector without using dec2binvec bvdata logical 11 10 1 0 O 0 putvalue dio bvdata Rules for Writing Digital Values Writing values to digital I O lines follows these rules Ifthe 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 When writing decimal values Ifthe value is too large to be represented by the lines contained by the device object then an error 1s returned Youcan write to a maximum of 32 lines To write to more than 32 lines you must use a binvec value When writing binvec values Youcan write to any number of lines There must be an element in the binary vector for each line you write to Youcan always read from a line configured for output Reading values is discussed in Read Digital Values on page 10 16 An error is returned if you write a negative value or if you write to a line configured for input 10 15 10 Digital Input Output 10 16 Read Digital Values 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 1s not stored
406. your system 1s 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 Create and Execute Callback Functions on page 7 47 or the example below Start and Stop a Digital 1 O 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 The stop function is issued An error occurred in the system When the device object stops Running is automatically set to Off Generate 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 Generate Timer Events Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2
407. ype and TriggerCondition Property Values for NI Hardware TriggerType Value TriggerCondition Value Description HwDigital NegativeEdge The trigger occurs when the negative falling edge of a digital signal is detected PositiveEdge The trigger occurs when the positive rising edge of a digital signal is detected HwAnalogChannelor AboveHighLevel The trigger occurs when the analog signal is HwAnalogPin above 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 LowHysteresis The trigger occurs when the analog signal is less than the specified low value with hysteresis given by the specified high value 7 38 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 Dev addchannel ai 0 7 ai TriggerType HwDigital The diagram below illustrates how you connect a digital trigger signal to an MIO 16E Series board PFIO TRIG1 corresponds to pin 11 Configure Analog Input Triggers TTL signal PFIO TRIG1 MIO
408. ypes on page 7 41 Record and Retrieve Event Information on page 7 44 Create and Execute Callback Functions on page 7 47 Use Callback Properties and Functions on page 7 49 Events and Callbacks Basics 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 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 callback function as the value for the associated callback property 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 Analog Input Callback Properties Event Type Property Name Data missed DataMissedFcn Input overrange InputOverRangeFcn Run time error RuntimeErrorFecn Samples acquired SamplesAcquiredFcn 7 41 7 Doing More with Analog Input 7 42 Event Type Property Name SamplesAcquiredFcnCount Start StartFen Stop StopFec
409. yping type function name You can view the help for any function by typing Product Capobilities help function name You can view the help for any session based function by typing help daq Session function name You can change the way any toolbox function works by copying and renaming the file then modifying your copy You can also extend the toolbox by adding your own files or by using it in combination with other products such as Signal Processing Toolbox or Instrument Control Toolbox MathWorks provides several related products that are especially relevant to the kinds of tasks you can perform with Data Acquisition Toolbox For more information about any of these products see http www mathworks com products daq related jsp For more information about using National Instruments and CompactDAQ devices see session based categories Supported Hardware The list of hardware supported by Data Acquisition Toolbox can change in each release since hardware support is frequently added The MathWorks Web site is the best place to check for the most up to date listing To see the full list of hardware that the toolbox supports visit the supported hardware page at www mathworks com products daq supportedio html For more information about unsupported hardware see Unsupported Hardware on page 2 11 1 Introduction to Data Acquisition Anatomy of a Data Acquisition Experiment In this section System
410. z 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 Acquire Data with a National Instruments Board Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB 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 Configure Data Acquisition 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 Analog Input Examples Note You cannot use the legacy interface on 64 bit MATLAB See About the Session Based Interface on page 14 2 to acquire and generate data on a 64 bit MATLAB You can run this example by typing daqdoc4 2 at the MATLAB Comma

Download Pdf Manuals

Related Search

Related Contents

SKU 0602101 闊冲搷璇存槑涔︿慨鏀?R(1) - X  Fujitsu TX100 User's Manual  HI 93530    LES PIÈCES DU PUZZLE  3LCD+Oneエンジン搭載により、圧倒的な美しさを再現。 12,000ルーメン  

Copyright © All rights reserved. Failed to retrieve file