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NI Dynamic Signal Acquisition User Manual

1. 200 0 0 25 0 5 0 75 1 0 Frequency Sample Rate fs Figure A 12 NI 446x Digital Filter Input Frequency Response with Low Frequency Alias Rejection Disabled Figure A 13 shows the response of the analog filter Figure A 13 illustrates the alias rejection for a tone that passes the digital filter by falling into one of the narrow bands centered on one of three sets of sample rate multiples One set of narrow bands centers on 32 f and succeeding multiples of 32 The other two sets center on 64 f and 128 f and succeeding multiples of 64 and 128 respectively The first set of x axis labels denotes the NI 446x sample rate in kS s The second set of x axis labels shows the frequency of an input signal which could pass through the digital filter at the given sampling rate In the following example the NI 446x is set to sample at 10 kS s A clean tone of 1 Vpk amplitude is sent to an input channel on the device If the input frequency is less than approximately 4 9 kHz 0 49 f it passes through the digital filter At 4 91 kHz the digital filter applies 3 dB attenuation The digital filter provides at least 120 dB of attenuation for frequency components above the Nyquist frequency However the digital filter can potentially admit aliases in the much higher frequency range from 1 275 MHz to 1 285 MHz 128 f the example sample rate of 10 kS s If National Instruments Corporation A 11 N
2. H H e Q RE gt fs 8 fs 32 fs 64 fs Frequency fes 2 fes 8 fes 16 fes fDAC 2 DAC Figure 2 4 Images After DAC Filter Some further inherent filtering occurs at the DAC because the data is digitally sampled and held at eight times f This filtering has a sinx x response yielding nulls at multiples of eight times f as shown in Figure 2 5 ZS Baseband Signal S a Images After the DAC Fee e o o L HL tl gt A 8f 16 f 24 fs 32 fs A0 fs 48 fs 56 fs 64 fs Frequency fDAC 2 fpac Figure 2 5 Signal After DAC Third a four pole analog filter with a fixed cut off at 243 kHz filters the remaining images as shown in Figure 2 6 oO 3 lt Baseband Signal e e e Q Oo gt k 8f 16 fy 24 fs 32 fs A0 fs 48 fs 56 fs 64 fs Frequency fes 2 fes 8 fes 16 fes Pac 2 PAC Figure 2 6 Signal After Analog Filters ni com NI Dynamic Signal Acquisition User Manual 2 16 Chapter 2 Dynamic Signal Acquisition Device Concepts Filter Delay Output filter delay the time required for digital data to propagate through the DAC and interpolation digital filters varies depending on the update rate for DACs For example the filter delay at 10 kS s for the NI 4461 is 38 5 update clock cycles This signal experiences a delay equal to 3 85 ms This delay is an important factor for stimulus response measurements control applications or any application where loop time is critical You often might want to maximize the sample rate and minim
3. pseudodifferential Q quantization error quantizer RC relative accuracy resolution rise time rising edge The technique used on a device to acquire a programmed number of samples after trigger conditions are met The technique used on a device to keep a continuous buffer filled with data so that when the trigger conditions are met the sample includes the data leading up to the trigger condition Pseudodifferential channels are all referred to a common ground but this ground is not directly connected to the computer ground Often this connection is made by a relatively low value resistor to give some isolation between the two grounds The inherent uncertainty in digitizing an analog value as a result of the finite resolution of the conversion process A device that maps a variable from a continuous distribution to a discrete distribution Resistor capacitor for example an RC network is a circuit consisting of a resistor and capacitor A measure in LSB of the linearity of an ADC It includes all nonlinearity and quantization errors It does not include offset and gain errors of the circuitry feeding the ADC The smallest signal increment that can be detected by a measurement system Resolution can be expressed in bits in proportions or as a percentage of full scale For example a system can have 12 bit resolution one part in 4 096 resolution and 0 0244 of full scale Generally the time for a signal
4. Chapter 3 Developing Your Dynamic Signal Acquisition Application Table 3 2 describes in more detail the steps outlined in Figure 3 2 Some steps might be optional depending on your application Refer to your NI application software documentation for more information about each step Table 3 2 Analog Output Application Steps Flowchart Step LabVIEW Step LabWindows CVI Step Create Task Create a task using the DAQ Assistant Create a task using the DAQ Assistant or or Create a task programmatically using Create a task programmatically using the following VIs the following functions e DAQmx Create Task VI e DAQmxCreateTask e DAQmx Create Virtual Channel VI DAQmxCreateAoVoltageChan DAQmx Timing VI e DAQmxCfgSampClkTiming e DAQmx Triggering VI e DAQmxAnlgEdgeStartTrig or e DAQmxC gDigEdgeStartTrig Configure One or more channel property node s One or more calls to Channels DAQmxSetChanAttribute Synthesize Common tools include VIs from the Common analysis tools include the Data Sound and Vibration Measurement functions in the LabWindows CVI Suite or Waveform Measurement VIs Advanced Analysis Libraryt Write Data DAQmx Write VI DAQmxWriteAnalog64 or other data writing function Start DAQmx Start Task VI DAQmxStartTask Generation Continue Loop around data synthesis and Loop around data synthesis and Generation DAQmx Write VI DAQmxWriteAnalog64 or other data writing function Stop DAQm
5. For configurations that specify multiple sample rates between different devices the slave devices must be a power of two of the master device sharing the clock For example if the master device has a sample rate 2 25 NI Dynamic Signal Acquisition User Manual Chapter 2 Dynamic Signal Acquisition Device Concepts of 100 kS s the slave devices can run at 50 kS s 25 kS s or 200 kS s but not at 40 kS s The slowest sample rate device in the system must export the start trigger Because the delta sigmas run at different rates you have different group delays among all devices running at different rates Master Sample Clock Timebase Synchronization Master Sample Clock Timebase synchronization occurs with one DSA device exporting its Sample Clock Timebase signal to all other devices in the system For a PXI system the master device must reside in the master timebase slot of the chassis because the master timebase slot has specific point to point routing called PXI Star to slots 3 through 14 on which it exports the clock A PXI system cannot synchronize boards with master sample timebase synchronization beyond slot 14 For PCI devices the clock is physically exported through a RTSI cable that you must attach to the back of all the devices in the system After you install the DSA devices complete the following steps to synchronize the hardware 1 Program the master device to share its Sample Clock Timebase to all the slave devices Thi
6. NET Languages without NI Application Software With the Microsoft NBT Framework version 1 1 or later you can use NI DAQmx to create applications using Visual CH and Visual Basic NET without Measurement Studio You need Microsoft Visual Studio NET 2003 or Microsoft Visual Studio 2005 for the API documentation to be installed The installed documentation contains the NI DAQmx API overview measurement tasks and concepts and function reference This help is fully integrated into the Visual Studio NET documentation To view the NI DAQmx NET documentation go to Start Programs National Instruments NI DAQ NI DAQmx NET Reference Help Expand NI Measurement Studio Help NI Measurement Studio NET Class Library Reference to view the function reference Expand NI Measurement Studio Help NI Measurement Studio NET Class Library Using the Measurement Studio NET Class Libraries to view conceptual topics for using NI DAQmx with Visual C and Visual Basic NET To get to the same help topics from within Visual Studio go to Help Contents Select Measurement Studio from the Filtered By drop down list and follow the previous instructions Device Documentation and Specifications NI DAQ 7 0 and later includes the Device Document Browser which contains online documentation for supported DAQ SCXI and switch devices such as help files describing device pinouts features and operation and PDF files of the printed device documents You can find
7. view and or print the documents for each device using the Device Document Browser at any time by inserting the CD After installing the Device Document Browser device documents are accessible from Start NI Dynamic Signal Acquisition User Manual xiv ni com About This Manual All Programs National Instruments NI DA Q Browse Device Documentation Training Courses If you need more help getting started developing an application with NI products NI offers training courses To enroll in a course or obtain a detailed course outline refer to ni com training Technical Support on the Web For additional support refer to ni com support or zone ni com ei Note You can download these documents at ni com manuals DAQ specifications and some DAQ manuals are available as PDFs You must have Adobe Acrobat Reader with Search and Accessibility 5 0 5 or later installed to view the PDFs Refer to the Adobe Systems Incorporated Web site at www adobe com to download Acrobat Reader Refer to the National Instruments Product Manuals Library at ni com manuals for updated documentation resources National Instruments Corporation XV NI Dynamic Signal Acquisition User Manual Getting Started Before installing the NI Dynamic Signal Acquisition DSA device you must install the software you plan to use with the device Installing NI DAQ You must install the latest version of NI DAQ before installing the DSA device Refer to the DAQ Ge
8. 2 21 analog to digital converter 2 8 ANSI C documentation xiv anti alias filters 2 8 anti imaging and interpolation filters 2 15 attenuation NI 446x only A 3 block diagrams A 5 A 22 BNC connector polarity A 8 A 24 National Instruments Corporation l 1 C calibration certificate NI resources B 2 chip DDS 2 19 choosing 2 2 2 13 conventions used in the manual ix coupling input 2 3 D DAC 2 14 DAQ assistant 3 1 DC coupling 2 3 DDS chip 2 19 decimation factor 2 10 Declaration of Conformity NI resources B 2 detection overload 2 6 devices A 1 diagnostic tools NI resources B 1 digital function block diagram A 15 digital triggering 2 20 digital to analog converter 2 14 distortion output 2 12 documentation conventions used in manual ix NI resources B 1 drivers NI resources B 1 E examples NI resources B 1 F features A 1 A 13 A 21 front panel diagrams A 7 A 16 A 22 NI Dynamic Signal Acquisition User Manual Index G gain NI 446x only A 3 getting started 1 1 H hardware installing 1 1 help technical support B 1 TEEE 1451 4 2 4 TEPE 2 5 impedance output NI PXI 4461 only 2 14 input 2 2 2 11 2 12 2 18 input coupling 2 3 installing hardware 1 1 instrument drivers NI resources B 1 K KnowledgeBase B 1 L low frequency alias rejection 2 10 Measurement Studio documentation xiii Measurement system overview 1 2
9. distortion caused by a clipped or overranged waveform can occur The NI USB 443x and NI 446x devices include overload detection in both the analog domain predigitization and digital domain postdigitization The NI 447x and 449x devices support digital domain overload detection An analog overrange can occur independently from a digital overrange and vice versa For example an IEPE accelerometer might have a resonant frequency that when stimulated can produce an overrange in the analog signal However because the ADC delta sigma technology uses very sharp anti aliasing filters the overrange is not passed into the digitized signal Conversely a sharp transient on the analog side might not overrange but the step response of the delta sigma anti aliasing filters might produce clipping in the digital data The NI USB 443x and NI 446x analog overload detection circuitry detects a clipped or overloaded condition You can programmatically poll the overload detection circuitry on a per channel basis to monitor for an overload condition If an overload is detected consider any data acquired at that time corrupt DSA devices perform digital overload detection as a percentage of the range The overload detection occurs before the device applies gain and offset corrections Detecting the overload before the gain and offset corrections catches an overflow condition in the delta sigma modulator or ADC filter For instance on some DSA devices the a
10. x Stop Task VI DAQmxStopTask Generation Clear Task DAQmx Clear Task VI DAQmxClearTask These steps might be optional depending on your application This library requires either the Full or Professional Development System of the NI application software National Instruments Corporation 3 7 NI Dynamic Signal Acquisition User Manual Chapter 3 Developing Your Dynamic Signal Acquisition Application B Note Table 3 2 provides example functions for LabWindows CVI In most cases LabWindows CVI code ports directly to other ANSI C environments including Microsoft Visual C If you are using other text based application software including NI Measurement Studio in a NET environment you might need to make minor changes in the function syntax Refer to your application software or the Analog Output Application Examples section of this chapter to view some example analog output applications Analog Output Application Examples NI DAQmx and all NI ADEs ship with examples you can use to get started with your application LabVIEW Example The following LabVIEW example illustrates a common continuous generation application Example Generation Application Cont Gen Voltage Wfm Int Clk Non Regeneration VI located in labview examples DAQmx Analog Out Generate Voltage 1llb LabWindows CVI Example The following LabWindows CVI example in the CVI folder illustrates a common continuous generation application Example G
11. 2 23 NI Dynamic Signal Acquisition User Manual Chapter 2 Dynamic Signal Acquisition Device Concepts Synchronization Some applications require tight synchronization between input and output operations on multiple devices Synchronization is important to minimize skew between channels or to eliminate clock drift between devices in long duration operations You can synchronize the analog input and output operations on two or more DSA devices to extend the channel count of DSA measurements Table 2 6 lists possible DSA device synchronization configurations to help you decide which method of synchronization to use 3 Note This section discusses synchronizing only DSA devices You can synchronize other NI products with DSA devices but the DSA device must be the master device Refer to the NI Developer Zone at ni com zone for more information about synchronizing other devices with DSA devices Table 2 6 Supported DSA Device Synchronization Configuration Reference Clock Master Sample Configuration PXI Only Clock Timebase 449x and 449x Supported 446x and 446x Supported Supported 4471x and 447x Supported 449x and 446x Supported 449x and 447x 446x and 447x t Supported Multrate synchronization is not supported The NI 446x must be the master DSA device Note NI USB 443x devices do not support synchronization Reference Clock Synchronization PXI PXle Only With r
12. 2 Dynamic Signal Acquisition Device Concepts Table 2 2 Decimation Factors for Given Sample Rates Continued Sample Rate Decimation Factor 6 4 kS s lt f lt 12 8 kS s 4 12 8 kS s lt f lt 25 6 kS s 2 Supported DSA Devices Not all DSA devices support low frequency alias rejection The following list provides more information about which devices support low frequency alias rejection e NI 446x devices e NI PXI 447x devices revision H and later e NI PCI 447x devices revision F and later e NI PCI 4474 devices revision B and later e NI 449x devices ei Note The AI EnhancedAliasRejectionEnable property is enabled by default for NI 446x and disabled for NI 447x and NI 449x for rates above 1 kS s devices Filter Delay The filter delay is the time required for data to propagate through a converter All DSA device channels have filter delays due to the presence of filter circuitry on both input and output channels To understand how a filter delay can affect your measurement consider an ADC digital filter with a delay of 63 sample clock samples At a 10 kS s sample rate the signal experiences a delay equal to 6 3 ms The filter delay is an important factor for stimulus response measurements control applications or any application where loop time is critical You often might maximize the sample rate and minimize the time required for the filter delay The input filter delay also makes an external digita
13. A Device Specific Information NI 447x Filter Response Figure A 18 shows the digital filter input frequency response 0 00 20 00 40 00 60 00 Amplitude dB 80 00 100 00 120 00 0 00 0 20 0 40 0 60 0 80 1 00 Frequency Sample Rate fg Figure A 18 NI 447x Digital Filter Input Frequency Response NI Dynamic Signal Acquisition User Manual A 18 ni com Appendix A Device Specific Information Figure A 19 shows the digital filter frequency response near the cut off point 0 00 3 00 Amplitude dB 5 00 6 00 0 43 0 44 0 45 0 46 0 47 0 48 0 49 0 50 Frequency Sample Rate fs Figure A 19 NI 447x Digital Filter Frequency Response Near the Cut off Point Figure A 20 shows the response of the analog filter Figure A 20 illustrates the alias rejection for a tone that passes the digital filter by falling into one of the narrow bands centered on 128 or 64 f The first set of x axis labels denotes the NI 447x sample rate in kS s The second set of x axis labels shows the frequency of an input signal which could pass through the digital filter at the given sampling rate In the following example the NI 447x is set to sample at 10 kS s A clean tone of 1 Vpk amplitude is sent to an input channel on the device If the input frequency is less than approximate
14. Analog Input Filters This section contains information about analog input filters Anti Alias Filters A digitizer or ADC might sample signals containing frequency components above the Nyquist limit The undesirable effect of the digitizer modulating out of band components into the Nyquist bandwidth is aliasing The greatest danger of aliasing is that you cannot determine whether aliasing occurred by looking at the ADC output If an input signal contains several frequency components or harmonics some of these components might be represented correctly while others contain aliased artifacts Lowpass filtering to eliminate components above the Nyquist frequency either before or during the digitization process can guarantee that the digitized data set is free of aliased components DSA devices employ both digital and analog lowpass filters to achieve this protection NI Dynamic Signal Acquisition User Manual 2 8 ni com Chapter 2 Dynamic Signal Acquisition Device Concepts The delta sigma ADCs on DSA devices include an oversampled architecture and sharp digital filters with cut off frequencies that track the sampling rate Thus the filter automatically adjusts to follow the Nyquist frequency Although the digital filter eliminates almost all out of band components it is still susceptible to aliases from certain narrow frequency bands defined by the following rules e When you select a sample rate greater than 102 4 kS s and less than or eq
15. Features Figure A 21 shows the NI 449x analog input circuitry block diagram Open Short 4mA a IEPE ff o On O 0 033 pF Differential Lowpass me l Amplifier Filter Cal C SE S10 Mo gt Ze ADC O Gain 0 10 20 30 ao 50 Q SLT Figure A 21 NI 449x Analog Input Block Diagram ei Note Certain NI 449x devices support different gain options Refer to the NI 449x Specifications for more information about supported gain settings The NI 449x input channels feature the following e Simultaneous sampling rates up to 204 8 kS s e Per channel selection of gain e Per channel IEPE current excitation National Instruments Corporation A 21 NI Dynamic Signal Acquisition User Manual Appendix A Device Specific Information e Per channel IEPE sensor open and short detect e Multiple triggering modes including external digital triggering e Per channel digital overload detection e Hardware data packing e TEDS NI 449x Block Diagram Figure A 22 shows the NI 449x block diagram ADC 0 1 Gain Offset Correction ADC 2 3 Interface Digital Filtering and Decimation rire Analog v Trigger Timing and ADC och Digital Trigger PFIO Triggering PCI PCle La gt Interface aN Ri kl Controller DDS PXI Trigger Bus PCI PCle B
16. NI Dynamic Signal Acquisition User Manual Appendix A Device Specific Information BNC Connector Polarity Figure A 6 shows the BNC connector polarity for all NI 446x devices Figure A 6 BNC Connector Polarity for NI 446x Devices NI 446x Input Connections Figure A 7 shows an NI 446x input connection with the NI 446x terminal configuration in differential mode Refer to the Analog Input Channel Configurations section of Chapter 2 Dynamic Signal Acquisition Device Concepts for more information about terminal configuration DUT 217 pF 1 MQ i E S77 Alo 7 imo So 223pF 77 Figure A 7 NI 446x Input Connection in Differential Mode NI Dynamic Signal Acquisition User Manual A 8 ni com Appendix A Device Specific Information Figure A 8 shows an NI 446x input connection with the NI 446x terminal configuration in pseudodifferential mode DUT ee 217 pF H MQ Alo 7 zma Figure A 8 NI 446x Terminal Configuration in Pseudodifferential Mode NI 4461 Output Connections Figure A 9 shows an NI 4461 output connection with the NI 4461 terminal configuration in differential mode Refer to the Analog Output Channel Configurations section of Chapter 2 Dynamic Signal Acquisition Device Concepts for more information about terminal configuration 119 4 8 KQ 4 8 KQ Figure A 9 NI 4461
17. Output Connection with Terminal Configuration in Differential Mode National Instruments Corporation A 9 NI Dynamic Signal Acquisition User Manual Appendix A Device Specific Information Figure A 10 shows an NI 4461 output connection with the NI 4461 terminal configuration in pseudodifferential mode 11 Load 11Q WW soa Figure A 10 NI 4461 Output Connection with Terminal Configuration in Pseudodifferential Mode NI 446x Filter Response Figure A 11 shows the digital filter input frequency response with low frequency alias rejection enabled 80 100 120 Attenuation dB 140 160 180 200 0 0 25 0 5 0 75 1 0 Frequency Sample Rate fs Figure A 11 NI 446x Digital Filter Input Frequency Response with Low Frequency Alias Rejection Enabled NI Dynamic Signal Acquisition User Manual A 10 ni com Appendix A Device Specific Information Figure A 12 shows the digital filter input frequency response with low frequency alias rejection disabled Attenuation dB 160 5 180
18. Table 2 1 to determine how to configure the channel Table 2 1 Analog Input Source Reference Channel Configuration Floating Pseudodifferential Grounded Differential or pseudodifferential The NI 446x is automatically configured for differential mode when powered on or powered off This configuration protects the 50 Q resistor on the negative pin Input Coupling You can configure each NI USB 443x NI 446x or NI 447x device AI channel for either AC or DC coupling If you select DC coupling any DC offset present in the source signal is passed to the ADC The DC coupling configuration is usually best if the signal source has only small amounts of offset voltage or if the DC content of the acquired signal is important If the source has a significant amount of unwanted offset select AC coupling to take full advantage of the input dynamic range ei Note The NI 449x allows AC coupling only Selecting AC coupling enables a highpass resistor capacitor RC filter into the positive and negative signal paths The filter time constant is 47 ms for the NI 446x NI 4472 and NI PCI 4474 The highpass RC filter settles to National Instruments Corporation 2 3 NI Dynamic Signal Acquisition User Manual Chapter 2 Dynamic Signal Acquisition Device Concepts 0 5 accuracy in 0 25 s in response to a step input It takes 0 782 s to settle to 24 bit accuracy in response to a step input The settling time is somewhat dependent on
19. at usr local natinst nidaqmx docs LabVIEW If you are a new user use the Getting Started with LabVIEW manual to familiarize yourself with the LabVIEW graphical programming environment and the basic LabVIEW features you use to build data acquisition and instrument control applications Open the Getting Started with LabVIEW manual by selecting Start All Programs National Instruments LabVIEW LabVIEW Manuals or by navigating to the labview manuals directory and opening Lv_Getting_Started pdf Use the LabVIEW Help available by selecting Help Search the LabVIEW Help in LabVIEW to access information about LabVIEW programming concepts step by step instructions for using LabVIEW and reference information about LabVIEW VIs functions palettes menus and tools Refer to the following locations on the Contents tab of the LabVIEW Help for information about NI DAQmx e Getting Started Getting Started with DAQ Includes overview information and a tutorial to learn how to take an NI DAQmx measurement in LabVIEW using the DAQ Assistant s VI and Function Reference Measurement I O VIs and Functions Describes the LabVIEW NI DAQmx VIs and properties e Taking Measurements Contains the conceptual and how to information you need to acquire and analyze measurement data in LabVIEW including common measurements measurement fundamentals NI DAQm x key concepts and device considerations If you use the LabVIEW Sound and Vibration Toolkit
20. by owner s failure to follow the National Instruments installation operation or maintenance instructions owner s modification of the product owner s abuse misuse or negligent acts and power failure or surges fire flood accident actions of third parties or other events outside reasonable control Copyright Under the copyright laws this publication may not be reproduced or transmitted in any form electronic or mechanical including photocopying recording storing in an information retrieval system or translating in whole or in part without the prior written consent of National Instruments Corporation National Instruments respects the intellectual property of others and we ask our users to do the same NI software is protected by copyright and other intellectual property laws Where NI software may be used to reproduce software or other materials belonging to others you may use NI software only to reproduce materials that you may reproduce in accordance with the terms of any applicable license or other legal restriction Trademarks National Instruments NI ni com and LabVIEW are trademarks of National Instruments Corporation Refer to the Terms of Use section on ni com legal for more information about National Instruments trademarks Other product and company names mentioned herein are trademarks or trade names of their respective companies Members of the National Instruments Alliance Partner Program are business entities
21. compared to the actual digitized data Although this trigger jitter is never greater than one sample period it might be significant when the sample rate is only twice the bandwidth of interest This jitter usually has no effect on data processing and you can decrease this jitter by sampling at a higher rate You can use several analog triggering modes with DSA devices including analog edge analog edge with hysteresis and window triggering Analog Edge Triggering For analog edge triggering configure the device to detect a certain signal Level and slope either rising or falling Figure 2 8 shows an example of rising edge analog triggering The trigger asserts when the signal starts below Level and then crosses above Level NEE EES Level Level and Slope of Signal Initiates Data Capture Figure 2 8 Analog Trigger Level National Instruments Corporation 2 21 NI Dynamic Signal Acquisition User Manual Chapter 2 Dynamic Signal Acquisition Device Concepts Analog Edge Triggering With Hysteresis When you add hysteresis to analog edge triggering you add a window above or below the trigger level This trigger often is used to reduce false triggering due to noise or jitter in the signal For example if you add a hysteresis of 1 V to the example in Figure 2 8 which uses a level of 3 2 V the signal must start at or drop below 2 2 V to arm the trigger The trigger asserts when the signal rises above 3 2 V and deasser
22. independent from National Instruments and have no agency partnership or joint venture relationship with National Instruments Patents For patents covering National Instruments products technology refer to the appropriate location Help Patents in your software the patents txt file on your media or the National Instruments Patent Notice at ni com patents WARNING REGARDING USE OF NATIONAL INSTRUMENTS PRODUCTS 1 NATIONAL INSTRUMENTS PRODUCTS ARE NOT DESIGNED WITH COMPONENTS AND TESTING FOR A LEVEL OF RELIABILITY SUITABLE FOR USE IN OR IN CONNECTION WITH SURGICAL IMPLANTS OR AS CRITICAL COMPONENTS IN ANY LIFE SUPPORT SYSTEMS WHOSE FAILURE TO PERFORM CAN REASONABLY BE EXPECTED TO CAUSE SIGNIFICANT INJURY TO A HUMAN 2 IN ANY APPLICATION INCLUDING THE ABOVE RELIABILITY OF OPERATION OF THE SOFTWARE PRODUCTS CAN BE IMPAIRED BY ADVERSE FACTORS INCLUDING BUT NOT LIMITED TO FLUCTUATIONS IN ELECTRICAL POWER SUPPLY COMPUTER HARDWARE MALFUNCTIONS COMPUTER OPERATING SYSTEM SOFTWARE FITNESS FITNESS OF COMPILERS AND DEVELOPMENT SOFTWARE USED TO DEVELOP AN APPLICATION INSTALLATION ERRORS SOFTWARE AND HARDWARE COMPATIBILITY PROBLEMS MALFUNCTIONS OR FAILURES OF ELECTRONIC MONITORING OR CONTROL DEVICES TRANSIENT FAILURES OF ELECTRONIC SYSTEMS HARDWARE AND OR SOFTWARE UNANTICIPATED USES OR MISUSES OR ERRORS ON THE PART OF THE USER OR APPLICATIONS DESIGNER ADVERSE FACTORS SUCH AS THESE ARE HEREAFTER COLLECTIVELY TERMED SYSTEM FAILURES AN
23. is fixed The analog filter response produces good high frequency alias rejection while maintaining a flat in band frequency response Because the analog filter is a two pole system the filter roll off is not extremely sharp The filter provides effective alias rejection at higher sampling rates where only very high frequencies in the previously mentioned susceptible areas can pass through the digital filter Some DSA devices support enhanced low frequency alias rejection The NI USB 443x NI 446x NI 447x and NI 449x devices have different filter response curves National Instruments Corporation 2 9 NI Dynamic Signal Acquisition User Manual Chapter 2 Dynamic Signal Acquisition Device Concepts Low Frequency Alias Rejection At very low sample rates between the minimum rate for the specific DSA device and 25 6 kS s the anti aliasing filters of DSA device AI channels might not completely reject all out of band signals The internal digital filter of the delta sigma ADC cannot suppress signals with frequencies near the multiples of the oversample rate sample rate multiplied by oversample factor DSA devices also employ fixed cutoff analog lowpass anti aliasing filters At low sample rates some multiples of the oversample rate can fall below the analog anti aliasing filter cut off frequency For example for a device using ADCs with an oversample factor of 128 f and sampling at a rate of 1 kS s the oversample rate is 128 kHz Some mult
24. noted NI 446x refers to the NI PCI 4461 NI PXI 4461 NI PCI 4462 and NI PXI 4462 unless otherwise noted NI 447x refers to the NI PCI 4472 NI PXI 4472 NI PCI 4474 NI PCI 4472B and NI PXI 4472B unless otherwise noted NI 449x refers to the any applicable bus version of NI 4495 NI 4496 and NI 4498 product unless otherwise noted Text in this font denotes a specific platform and indicates that the text following it applies only to that platform Related Documentation Each application software package and instrument driver includes information about writing applications for taking measurements and controlling measurement devices The following references to documents assume you have NI DAQmx 8 8 or later and where applicable version 8 x or later of the NI application software NI Dynamic Signal Acquisition User Manual X ni com About This Manual Refer to the National Instruments Product Manuals Library at ni com manuals for updated documentation resources The following documents contain information that you might find helpful as you use this manual NI DAQ The DAQ Getting Started Guide describes how to install your NI DAQmx for Windows software your NI DAQmx supported DAQ device and how to confirm that your device is operating properly Select Start All Programs National Instruments NI DAQ DAQ Getting Started Guide The NI DAQ Readme lists which devices are supported by this version of NI DAQ Select S
25. the DUT impedance as well The NI 4472B and NI 449x have a larger time constant 330 ms It takes 5 5 s to settle to 24 bit accuracy in response to a step input The NI USB 4431 has a time constant of 0 2 seconds and takes 3 4 seconds to settle to 24 bits The NI USB 4432 has a time constant of 1 75 seconds and takes 30 0 seconds to settle to 24 bits 3 Note NI DAQmx does not compensate for the settling time introduced by the RC filter when switching from DC to AC coupling To compensate for the filter settling time you can discard the samples taken during the settling time or force a delay before you restart the measurement You must force the delay after the AI task is committed but before the task starts Using AC coupling results in an attenuation of the low frequency response of the AI circuitry Refer to the NI USB 443x Specifications NI 446x Specifications NI 447x Specifications and NI 449x Specifications for information about cut off frequency for each device TEDS Transducer Electronic Data Sheet TEDS capable sensors carry a built in self identification EEPROM that stores a table of parameters and sensor information TEDS sensors have two modes of operation an analog mode which allows the sensors to operate as transducers measuring physical phenomena and a digital mode which allows the user to write and read information to and from the TEDS The NI USB 443x NI PCI 4461 NI 4462 and NI 449x support modes for Class I TED
26. the LabVIEW Order Analysis Toolkit or the Sound and Vibration Measurement Suite you can use the LabVIEW Help to access information about Sound and Vibration or Order Analysis VIs functions and palettes You also can use the user manuals for each toolkit to access information about sound and vibration or order analysis concepts NI Dynamic Signal Acquisition User Manual xii ni com LabWindows CVI About This Manual The Data Acquisition book of the LabWindows CVI Help contains measurement concepts for NI DAQmx This book also contains Taking an NI DAQmx Measurement in LabWindows CVI which includes step by step instructions about creating a measurement task using the DAQ Assistant In LabWindows CVI select Help Contents then select Using LabWindows CVI Data Acquisition The NI DAQmx Library book of the LabWindows CVI Help contains API overviews and function reference for NI DAQmx Select Library Reference NI DAQmx Library in the LabWindows CVI Help Measurement Studio If you program your NI DAQmx supported device in Measurement Studio using Visual C Visual C or Visual Basic NET you can interactively create channels and tasks by launching the DAQ Assistant from MAX or from within Visual Studio NET You can generate the configuration code based on your task or channel in Measurement Studio Refer to the DAQ Assistant Help for additional information about generating code You also can create channels and tasks and write
27. the overall rms signal level to the rms noise level expressed in decibels A programmed event that triggers an event such as data acquisition A method of triggering in which you trigger an operation using software NI Dynamic Signal Acquisition User Manual Glossary synchronous system noise TEDS THD THD N transducer transfer rate tp treset trigger TTL TTL compatible U undersampling Hardware a property of an event that is synchronized to a reference clock software a property of a function that begins an operation and returns only when the operation is complete A measure of the amount of noise seen by an analog circuit or an ADC when the AI channels are grounded Transducer electronic data sheet a transducer with a built in self identification EEPROM as standardized by IEEE 1451 4 Total harmonic distortion the ratio of the total rms signal due to harmonic distortion to the overall rms signal Usually expressed in decibels or as a percentage of the signal THD plus noise the ratio in decibels of the rms signal of harmonic distortion plus noise introduced to the overall rms signal See sensor The rate measured in bytes s at which data is moved from source to destination after software initialization and set up operations the maximum rate at which the hardware can operate The interval between pulses in a pulse train The length of the reset period Any event that causes or star
28. to the filter delay in the ADC When you use digital triggering the ADCs begin generating digital data immediately after receiving the digital trigger signal However the analog signal entering the ADCs is still subject to the filter delay This circumstance means that when the trigger is received the analog levels at the front of the ADCs are not digitized until a certain number of sample intervals later You can observe this behavior with an experiment Connect the same TTL signal to the external digital trigger input and to an AI channel Configure the acquisition to respond to a digital trigger The rising edge of the trigger does not appear in the digitized waveform until a specific number of samples pass Refer to the NJ USB 443x Specifications NI 446x Specifications NI 447x Specifications and NI 449x Specifications for more information about filter delay Analog triggering is performed on the digital output of the ADC The analog trigger circuit on a DSA device is a digital comparator Because the trigger is located after the ADC in the signal path the filter delay is not evident in the acquired data If the analog trigger is configured with a rising edge and a level of 1 0 V the voltage of the first sample is just above 1 0 V ei Note NI USB 4431 and NI 4461 You must also consider the AO filter delay in your application The digital filter introduces a deterministic delay during AO operations National Instruments Corporation
29. where the 0 dB reference is the default input range of 10 V Refer to the NI 446x Specifications for detailed information about each gain setting and corresponding range Caution The range for the 20 dB setting corresponds to a maximum input range of 42 4 Va Setting the gain to 20 dB attenuates the signal by a factor of 10 implying a maximum ADC range of 100 V However the analog front end circuitry is not rated beyond 42 4 V px When you use this gain setting the ADC does not saturate at 42 4 Nu however you risk damaging the measurement system or creating a possible safety hazard if you exceed the maximum rated input of 42 4 Vpk Table A 1 shows the gain setting sources Table A 1 Gain Setting Sources Gain Setting dB Source 0 10 20 30 Differential amplifier 10 Combination of 20 and 10 gains 20 Resistor divider network In general select the voltage range that provides the greatest dynamic range and the least distortion For example consider an accelerometer with a 100 mV g sensitivity rating with an absolute maximum output voltage of 5 Vpk In this case the 10 Vpk is appropriate corresponding to 0 dB gain However the 3 16 Vpk setting maximizes the dynamic range if you know the stimulus is limited to for example 20 g or 2 Vpk Minimize system distortion by providing sufficient headroom between the stimulus setting 2 Vpk in this instance and the range Choose the next high
30. your own applications in your ADE using the NI DAQmx API For help with NI DAQmx methods and properties refer to the NI DAQmx NET Class Library or the NI DAQmx Visual C Class Library included in the NJ Measurement Studio Help For general help with programming in Measurement Studio refer to the NJ Measurement Studio Help which is fully integrated with the Microsoft Visual Studio NET help To view this help file in Visual Studio NET select Measurement Studio NI Measurement Studio Help To create an application in Visual C Visual C or Visual Basic NET follow these general steps 1 In Visual Studio NET select File gt New Project to launch the New Project dialog box 2 Find the Measurement Studio folder for the language you want to create a program in 3 Choose a project type You add DAQ tasks as a part of this step National Instruments Corporation xiii NI Dynamic Signal Acquisition User Manual About This Manual ANSI C without NI Application Software The NI DAQmx Help contains API overviews and general information about measurement concepts Select Start All Programs National Instruments NI DAQ NI DAQmx Help The NI DAQmx C Reference Help describes the NI DAQm x Library functions which you can use with National Instruments data acquisition devices to develop instrumentation acquisition and control applications Select Start All Programs National Instruments NI DAQ NI DAQmx C Reference Help
31. 08 National Instruments Corporation All rights reserved Important Information Warranty The NI USB 4431 4432 NI 4461 4462 NI 4472 4472B 4474 and NI 4495 4496 4498 are warranted against defects in materials and workmanship for a period of one year from the date of shipment as evidenced by receipts or other documentation National Instruments will at its option repair or replace equipment that proves to be defective during the warranty period This warranty includes parts and labor The media on which you receive National Instruments software are warranted not to fail to execute programming instructions due to defects in materials and workmanship for a period of 90 days from date of shipment as evidenced by receipts or other documentation National Instruments will at its option repair or replace software media that do not execute programming instructions if National Instruments receives notice of such defects during the warranty period National Instruments does not warrant that the operation of the software shall be uninterrupted or error free A Return Material Authorization RMA number must be obtained from the factory and clearly marked on the outside of the package before any equipment will be accepted for warranty work National Instruments will pay the shipping costs of returning to the owner parts which are covered by warranty National Instruments believes that the information in this document is accurate The document has been
32. 431 is rated to drive a minimal load of 1 kQ However you can achieve optimal performance with larger load resistances such as 10 kQ or 100 kQ Refer to the NI USB 443x Specifications and NI 446x Specifications for more information Analog Output Channel Configurations The NI 4461 supports two terminal configurations for analog output differential and pseudodifferential The term pseudodifferential refers to the fact that there is a 50 Q or 1 KQ resistor between the outer connector shell and chassis ground The NI USB 4431 only supports pseudodifferential ei Note Attach all DSA devices to the chassis with screws to provide a reliable ground connection If you are using a PXI device be sure to tighten the screws at the top and bottom of the front face of the module If you are using a PCI device keep the screw that held the PCI slot cover to the computer chassis Reinsert this screw to securely attach the device NI Dynamic Signal Acquisition User Manual 2 12 ni com Chapter 2 Dynamic Signal Acquisition Device Concepts Choosing Channel Configurations If the signal source or DUT inputs are floating use the pseudodifferential configuration You must provide a ground reference for a floating signal If you do not provide a ground reference point for example selecting differential mode with a floating microphone or shaker table input amplifier with differential inputs the outputs or inputs can drift outside the device common mode ra
33. 49x devices Figure A 24 BNC Connector Polarity for NI 449x Devices NI Dynamic Signal Acquisition User Manual A 24 ni com NI 449x Filter Response Figure A 25 shows the digital filter input frequency response with low frequency alias rejection enabled Appendix A Device Specific Information 100 120 Attenuation dB 140 160 180 200 0 0 25 0 5 0 75 1 0 Frequency Sample Rate fs National Instruments Corporation Figure A 25 NI 449x Digital Filter Input Frequency Response with Low Frequency Alias Rejection Enabled A 25 NI Dynamic Signal Acquisition User Manual Appendix A Device Specific Information Figure A 26 shows the digital filter input frequency response with low frequency alias rejection disabled x 20 L N E Attenuation dB l E CH L A 2 160 f 180 200 0 0 25 0 5 0 75 1 0 Frequency Sample Rate fs Figure A 26 NI 449x Digital Filter Input Frequency Response with Low Frequency Alias Rejection
34. A high accuracy circuit that samples at a higher rate than needed and pushes the quantization noise above the frequency range of interest This out of band noise is typically removed by digital filters A plug in board that can contain multiple channels and conversion devices SCXI modules are distinct from devices An AIl consisting of two terminals not connected to a fixed reference such as the earth or a building ground A two terminal measurement configuration in which you do not need to connect either input to a fixed reference such as the earth or a building ground A TTL level signal having two discrete levels a high and a low level NI Dynamic Signal Acquisition User Manual G 4 ni com digital tuning word DIO DMA DNL DoC DOC down counter drivers DSA DUT dynamic range E ESD event external trigger F falling edge fi DAC National Instruments Corporation G 5 Glossary A 32 bit word that selects the DDS clock frequency Digital input output Direct memory access a method by which data can be transferred to from computer memory from to a device or memory on the bus while the processor does something else DMA is the fastest method of transferring data to from computer memory Differential nonlinearity a measure in LSBs of the worst case deviation of code widths from their ideal value of 1 LSB Declaration of Conformity Canadian Department of Communications Performing frequenc
35. DAQmx Help or the LabVIEW Help for more information about NI DAQm x properties This library requires either the Full or Professional Development System of the NI application software ei Note Table 3 1 provides example functions for LabWindows CVI In most cases LabWindows CVI code ports directly to other ANSI C environments including Microsoft Visual C If you are using other text based application software including NI Measurement Studio in a NET environment you might need to make minor changes in the function syntax Refer to your application software or the Analog Input Application Examples section of this chapter to view some example analog input applications Analog Input Application Examples NI DAQmx and all NI ADEs ship with examples you can use to get started with your application LabVIEW Examples The following LabVIEW examples illustrate common DSA analog input applications e Example Acceleration Application Cont Acq Accel Samples Int Clk Analog Start VI located in labview examples DAQmx Analog In Measure Acceleration 11b e Example Sound Pressure Application Cont Acq Snd Pressure Samples Int Clk VI located in labview examples DAQmx Analog In Measure Sound Pressure 1llb NI Dynamic Signal Acquisition User Manual 3 4 ni com Chapter 3 Developing Your Dynamic Signal Acquisition Application LabWindows CVI Examples The following LabWindows CVI examples in the CVI folder illustrate common DSA ana
36. Disabled NI 449x Reference Clock Synchronization NI 449x devices employ onboard PLL circuitry The PLL circuitry locks the onboard 100 MHz voltage controlled crystal oscillator VCXO to the PXI PXIe 10 MHz reference clock signal PXI_CLK10 The VCXO output provides the source for the DDS chip which generates the sample clock timebase In this way the NI PXI 449x devices lock the sample clock timebase to PXI_CLK10 NI 449x Specifications Refer to the NI 449x Specifications for more detailed information about the NI 449x devices NI Dynamic Signal Acquisition User Manual A 26 ni com Technical Support and Professional Services Visit the following sections of the award winning National Instruments Web site at ni com for technical support and professional services National Instruments Corporation Support Technical support at ni com support includes the following resources Self Help Technical Resources For answers and solutions visit ni com support for software drivers and updates a searchable KnowledgeBase product manuals step by step troubleshooting wizards thousands of example programs tutorials application notes instrument drivers and so on Registered users also receive access to the NI Discussion Forums at ni com forums NI Applications Engineers make sure every question submitted online receives an answer Standard Service Program Membership this program entitles members to direct acces
37. I Dynamic Signal Acquisition User Manual Appendix A Device Specific Information noise in the input signal falls into this narrow window the noise is not rejected by the digital filter In this limited frequency range you must consider the response of the analog filter Figure A 13 illustrates that with a sampling rate of 10 kS s the analog filter attenuates an input signal frequency of 1 28 MHz by 10 dB The sawtooth line in Figure A 13 represents the filter response with low frequency alias rejection enabled The worst case alias rejection is approximately 25 dB This corresponds to the analog filter attenuation at 25 6 kS s 5 0 0 0 5 0 10 0 15 0 20 0 25 0 7 30 0 2 35 0 N Analog Filter Response dB 40 0 eg Kal Ba e DE EE 45 0 50 0 Sample Rate kS s 1 0 Input Frequency 128 kHz 10 0 100 0 204 8 1000 0 1 28 MHz 6 4 MHz 128 fs 64 fe 32 fy Figure A 13 NI 446x Analog Filter Response This situation represents the set of worst case alias rejections for each sample rate You would only observe this worst case scenario with a well defined tone in a narrow frequency range In real measurement situations it is more likely that any energy passing the digital filter consists only of low amplitude noise If an unwanted component does appear in
38. LabVIEW or LabWindows CVI National Instruments Corporation 3 1 NI Dynamic Signal Acquisition User Manual Chapter 3 Developing Your Dynamic Signal Acquisition Application Figure 3 1 shows a typical flowchart for programming an analog input task taking a measurement and clearing the task No Create Task Yes Programmatically y Create a Task Programmatically Create Task and Channels y in DAQ Assistant N DAQ Assistan Create Al Channels Yy Configure Channels Optional y Specify Triggering Optional r Configure Timing p gt Start gt Read Samples m Analyze Data Optional y Display Data Optional Yes Read More Samples Stop Optional E e Clear Figure 3 1 Analog Input Task Flowchart NI Dynamic Signal Acquisition User Manual 3 2 ni com Chapter 3 Developing Your Dynamic Signal Acquisition Application Table 3 1 describes in more detail the steps outlined in the previous figure Some steps might be optional depending on your application Refer to your NI application software for more information about each step Table 3 1 Analog Input Application Steps Flowchart LabVIEW LabWindows CVI Step Step Step Create Task Create a task using the DAQ Assistant Create a task using the DAQ Assistant or or Create a task programmatically u
39. NI 447x Specifications and NI 449x Specifications for additional trigger requirements DSA devices also offer digital triggering in response to signals on the PXI or RTSI trigger bus Use any line from PXI_Trig lt 0 6 gt or RTSI lt 0 6 gt One exception applies when synchronizing multiple NI PXI 447x devices PXI_Trig 5 is reserved for internal use As with external digital triggering you can program the device to respond to either the rising or falling signal edge Ei Note The NI USB 443x devices have eight PFI lines for triggering NI Dynamic Signal Acquisition User Manual 2 20 ni com Chapter 2 Dynamic Signal Acquisition Device Concepts Analog Triggering You can configure the DSA device analog trigger circuitry to monitor any input channel from which you acquire data Choosing an input channel as the trigger channel does not influence the input channel acquisition capabilities The trigger circuit generates an internal digital trigger based on the input signal and the user defined trigger levels For example you can configure the device to start acquiring samples after the input signal crosses a specific threshold You also can route this internal trigger to the PXI or RTSI trigger bus to synchronize the start of the acquisition operation by one device with the operation of other devices in the system During repetitive triggering on a waveform you might observe jitter because of the uncertainty of where a trigger level falls
40. NI Dynamic Signal Acquisition NI Dynamic Signal Acquisition User Manual August 2008 lt 7 NATIONAL 3712356 01 P INSTRUMENTS Worldwide Technical Support and Product Information ni com National Instruments Corporate Headquarters 11500 North Mopac Expressway Austin Texas 78759 3504 USA Tel 512 683 0100 Worldwide Offices Australia 1800 300 800 Austria 43 662 457990 0 Belgium 32 0 2 757 0020 Brazil 55 11 3262 3599 Canada 800 433 3488 China 86 21 5050 9800 Czech Republic 420 224 235 774 Denmark 45 45 76 26 00 Finland 358 0 9 725 72511 France 01 57 66 24 24 Germany 49 89 7413130 India 91 80 41190000 Israel 972 3 6393737 Italy 39 02 41309277 Japan 0120 527196 Korea 82 02 3451 3400 Lebanon 961 0 1 33 28 28 Malaysia 1800 887710 Mexico 01 800 010 0793 Netherlands 31 0 348 433 466 New Zealand 0800 553 322 Norway 47 0 66 90 76 60 Poland 48 22 3390150 Portugal 351 210 311 210 Russia 7 495 783 6851 Singapore 1800 226 5886 Slovenia 386 3 425 42 00 South Africa 27 0 11 805 8197 Spain 34 91 640 0085 Sweden 46 0 8 587 895 00 Switzerland 41 56 2005151 Taiwan 886 02 2377 2222 Thailand 662 278 6777 Turkey 90 212 279 3031 United Kingdom 44 0 1635 523545 For further support information refer to the Technical Support and Professional Services appendix To comment on National Instruments documentation refer to the National Instruments Web site at ni com info and enter the info code feedback 2004 20
41. S sensors without any additional hardware The NI 447x devices require an accessory such as the BNC 2096 to allow the user to digitally communicate with the EEPROM on Class I TEDS sensors TEDS contains information about the sensor such as calibration sensitivity and manufacturer information This information is accessible in Measurement amp Automation Explorer MAX VIs in LabVIEW or by calling the equivalent function calls in a text based ADE NI Dynamic Signal Acquisition User Manual 2 4 ni com Chapter 2 Dynamic Signal Acquisition Device Concepts Refer to the following installed help files for more information about TEDS e Measurement amp Automation Explorer Help for NI DAQmx Contains information on configuring and testing data acquisition DAQ devices RT Series DAQ devices SCXI devices SCC devices TEDS carriers and RTSI cables using Measurement amp Automation Explorer MAX for NI DAQm x and special considerations for operating systems Select Help Help Topics NI DAQmx MAX Help for NI DAQmx in MAX e NI DAQmx Help Contains general information about measurement concepts key NI DAQmx concepts and common applications that are applicable to all programming environments Select Start All Programs National Instruments NI DAQ NI DAQmx Help e LabVIEW Help Contains information about LabVIEW programming concepts step by step instructions for using LabVIEW and reference information about LabVIEW VIs function
42. Signals to NI 447x Devices This section contains information about connecting signals to NI 447x devices NI 447x Front Panels Figure A 16 shows the NI PXI 4472 NI PXI 4472B NI PCI 4472 NI PCI 4472B and NI PCI 4474 front panels NATIONAL NATIONAL INSTRUMENTS INSTRUMENTS NI PXI 4472 NI PXI 4472B d CHO CH1 CH2 CH3 AA JS E L NI PXI 4472 NI PXI 4472B NI PCI 4472 4472B NI PCI 4474 Figure A 16 NI 447x Front Panels NI Dynamic Signal Acquisition User Manual A 16 ni com Appendix A Device Specific Information NI 447x Input Connections The NI 447x channels have pseudodifferential inputs Figure A 17 shows the input configurations for floating and grounded signal sources Floating Source CHn Se Signal Ground 1MQ 50 Q Grounded Source CHn gt Signal Ground TMO 50 Q Figure A 17 NI 447x Input Connections UN Caution Connecting a signal that varies more than 2 5 V from the NI 447x ground reference to the ground shield of any input channel can result in inaccurate measurements or damage to the device NI is not responsible for damage caused by such connections National Instruments Corporation A 17 NI Dynamic Signal Acquisition User Manual Appendix
43. Y APPLICATION WHERE A SYSTEM FAILURE WOULD CREATE A RISK OF HARM TO PROPERTY OR PERSONS INCLUDING THE RISK OF BODILY INJURY AND DEATH SHOULD NOT BE RELIANT SOLELY UPON ONE FORM OF ELECTRONIC SYSTEM DUE TO THE RISK OF SYSTEM FAILURE TO AVOID DAMAGE INJURY OR DEATH THE USER OR APPLICATION DESIGNER MUST TAKE REASONABLY PRUDENT STEPS TO PROTECT AGAINST SYSTEM FAILURES INCLUDING BUT NOT LIMITED TO BACK UP OR SHUT DOWN MECHANISMS BECAUSE EACH END USER SYSTEM IS CUSTOMIZED AND DIFFERS FROM NATIONAL INSTRUMENTS TESTING PLATFORMS AND BECAUSE A USER OR APPLICATION DESIGNER MAY USE NATIONAL INSTRUMENTS PRODUCTS IN COMBINATION WITH OTHER PRODUCTS IN A MANNER NOT EVALUATED OR CONTEMPLATED BY NATIONAL INSTRUMENTS THE USER OR APPLICATION DESIGNER IS ULTIMATELY RESPONSIBLE FOR VERIFYING AND VALIDATING THE SUITABILITY OF NATIONAL INSTRUMENTS PRODUCTS WHENEVER NATIONAL INSTRUMENTS PRODUCTS ARE INCORPORATED IN A SYSTEM OR APPLICATION INCLUDING WITHOUT LIMITATION THE APPROPRIATE DESIGN PROCESS AND SAFETY LEVEL OF SUCH SYSTEM OR APPLICATION Compliance Electromagnetic Compatibility Information This hardware was tested and complies with applicable regulatory requirements and limits for electromagnetic compatibility EMC as indicated in the Declaration of Conformity DoC of this hardware These requirements and limits are designed to provide reasonable protection against harmful interference when the hardware is operated in the electromagnetic environment i
44. alog Output Application Overview eee eeceseeeeeseeseeeneeeeees 3 5 Analog Output Application Examples 0 00 0 eceeeeseeeeeseeseeeeceeeeseeseeeseenees 3 8 Lab VIEW Eeler gester Ae deene eege Cl 3 8 LabWindows CVI Example eceeceeceseesecseeeeeeseeeeesseeeeeeseeenees 3 8 NI Dynamic Signal Acquisition User Manual vi ni com Contents Synchronization Applications 0 0 0 eee eeeeseescceseceecesesesesseceeeeseeseeeaecseeeaeenseeaesneeeaeenaes 3 8 Synchronization Application Overview ccc eeessecseeeseeseeeseeseeeaeeseeeaeens 3 8 Synchronization Application Examples 0 eeceeeeseeeeceseeseeeeeseeeseeneeeaeens 3 9 LabVIEW e un UE 3 9 LabWindows CVI Example ceseeeeceeseeseeeseceeeesecneetseeneeeseenaes 3 9 Appendix A Device Specific Information IR A 1 UE ve lsc cet ststeseshavhedevazhs dees elusuddeevesuads desdpate desvevedsdeeeecetbeeleuy A 1 NI 446x Analog Input Features 0 0 eee eeeeeerecneeeeeeeeseenees A 1 NI 4461 Analog Output Features A 3 NI 446x Gain and Attenuaton cc ceeeseeseceeeseeeseceecesecsesesesseseneesees A 3 NIT446x Block Diagrams erus e etae aa e h ASE eEeed A 5 NI 4461 Block Diagrames a a E oee A 5 INI 4462 BlOCK Dia grain ccenn EK EEEE A 6 Connecting Signals to NI 446x Devices 00 eeeeseeseeeeeeeceseteeeseeseeeseesees A 7 NI 446x Front Panel Sennaa caad cic ses ee a aai ani A 7 BNC Connector Polarity iieis einser srani aeeaiei A 8 NI 446x Input Connections s essesseseseseeesreersresrs
45. amic Signal Acquisition User Manual Chapter 2 ADC Dynamic Signal Acquisition Device Concepts when measuring voltages capable of producing an overload condition when you use the 42 4 V px range or 20 dB gain setting Each ADC in a DSA device uses a conversion method known as delta sigma modulation If the desired data rate is 51 2 kS s each ADC actually samples its input signal at 6 5536 MS s 128 times the data rate producing 1 bit samples that are sent to a digital filter This filter rejects signal components greater than the Nyquist frequency of 25 6 kHz The 1 bit 6 5536 MS s data stream from the ADC contains all of the information necessary to produce 24 bit samples at 51 2 kS s The delta sigma ADC achieves this conversion from high speed to high resolution with a technique called noise shaping The ADC adds random noise to the signal so that the resulting quantization noise although large is restricted to frequencies above the Nyquist frequency 25 6 kHz in this case This noise is not correlated with the input signal and is almost completely rejected by the digital filter The resulting output of the filter is a band limited signal with a large dynamic range One of the advantages of a delta sigma ADC is that it uses a 1 bit DAC as an internal reference As a result the delta sigma ADC is free from the differential nonlinearity DNL and associated noise inherent in high resolution ADCs using other conversion techniques
46. art time of an acquisition and gather data at a known position in time relative to a trigger signal Frequency components that are integral multiples of a fundamental frequency In logic circuits designed to have three possible states 0O 1 and tristate high impedance the high impedance state effectively removes the output from its circuit and can be used to simplify bus communication by wire ANDing tristate inputs Triggering with a trigger condition based on both current analog signal levels and the past signal history For example a hysteresis trigger can be set to fire when a signal rises above 0 V but only if it fell below 0 V at some point in the past Hertz cycles per second Specifically refers to the repetition frequency of a waveform Integrated electronic piezoelectric a type of transducer that operates using a constant current source as the conditioning medium and returns a signal in the form of voltage modulation on the same line as the current source Unwanted frequency components beyond the Nyquist bandwidth produced during D A conversion during analog output operations Intermodulation distortion the ratio in dB of the total rms signal level of harmonic sum and difference distortion products to the overall rms signal level The test signal is two sine waves added together according to the CCIF standard of one 14 kHz sine wave and one 15 kHz sine wave added in a 1 1 amplitude ratio Inches NI Dynami
47. c Signal Acquisition User Manual Glossary INL input impedance interrupt kS L LabVIEW linearity LSB memory buffer MSB Integral nonlinearity a measure in LSB of the worst case deviation from the ideal A D or D A transfer characteristic of the analog I O circuitry The measured resistance and capacitance between the input terminals of a circuit and ground A computer signal indicating that the CPU should suspend its current task to service a designated activity Kilo the standard metric prefix for 1 000 or 103 used with units of measure such as volts hertz and meters 1 000 samples A program development application based on the programming language G and used commonly for test and measurement purposes The adherence of device response to the equation R K1S K2 where R response S stimulus and K1 K2 constants Least significant bit the bit of a digital word that has the lowest numerical value See buffer Most significant bit the bit of a digital word that has the highest numerical value NI Dynamic Signal Acquisition User Manual G 8 ni com noise nonreferenced signal sources Nyquist bandwidth Nyquist frequency Nyquist Sampling Theorem 0 overrange oversampling P passband PCI PFI National Instruments Corporation G 9 Glossary An undesirable electrical signal noise comes from external sources such as the AC power line motors generator
48. carefully reviewed for technical accuracy In the event that technical or typographical errors exist National Instruments reserves the right to make changes to subsequent editions of this document without prior notice to holders of this edition The reader should consult National Instruments if errors are suspected In no event shall National Instruments be liable for any damages arising out of or related to this document or the information contained in it EXCEPT AS SPECIFIED HEREIN NATIONAL INSTRUMENTS MAKES NO WARRANTIES EXPRESS OR IMPLIED AND SPECIFICALLY DISCLAIMS ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE CUSTOMER S RIGHT TO RECOVER DAMAGES CAUSED BY FAULT OR NEGLIGENCE ON THE PART OF NATIONAL INSTRUMENTS SHALL BE LIMITED TO THE AMOUNT THERETOFORE PAID BY THE CUSTOMER NATIONAL INSTRUMENTS WILL NOT BE LIABLE FOR DAMAGES RESULTING FROM LOSS OF DATA PROFITS USE OF PRODUCTS OR INCIDENTAL OR CONSEQUENTIAL DAMAGES EVEN IF ADVISED OF THE POSSIBILITY THEREOF This limitation of the liability of National Instruments will apply regardless of the form of action whether in contract or tort including negligence Any action against National Instruments must be brought within one year after the cause of action accrues National Instruments shall not be liable for any delay in performance due to causes beyond its reasonable control The warranty provided herein does not cover damages defects malfunctions or service failures caused
49. ceive noise from the environment that could affect measurement accuracy To ensure proper shielding effectiveness of connected coaxial cables the outer conductor must be directly connected to chassis or earth ground at the load end of the cable In addition snap on ferrite beads or other remedial measures may be required to prevent unwanted emissions or immunity Refer to the specifications of your product for more information about EMC performance DSA devices typically have a dynamic range of more than 110 dB Several factors can degrade the noise performance of input channels such as noise picked up from nearby electronic devices DSA devices work best when kept as far away as possible from other plug in devices power supplies disk drives and computer monitors Cabling is also critical Use well shielded coaxial or floating cables for all connections Route the National Instruments Corporation 2 1 NI Dynamic Signal Acquisition User Manual Chapter 2 Dynamic Signal Acquisition Device Concepts Analog Input cables away from sources of interference such as computer monitors switching power supplies and fluorescent lights Physical motion or deformation can induce noise on sensitive analog cables Use a transducer with a low output impedance to minimize system susceptibility to external noise sources and crosstalk You can reduce the effects of noise on your measurements by carefully choosing the sample rate to maximize the effectivene
50. condition Power Off and Power Loss When the NI USB 4431 and NI 4461 are powered down or lose power the output channels assume a high impedance state The NI 4461 for instance drops to 0 0 V in approximately 8 us Figure 2 7 illustrates the typical behavior of an NI USB 4431 and NI 4461 generating 10 V when powered off or when the device loses power Voltage V A Time us Figure 2 7 Power Off and Power Loss Behavior NI Dynamic Signal Acquisition User Manual 2 18 ni com Chapter 2 Dynamic Signal Acquisition Device Concepts Timing and Triggering This section contains information about timing and triggering theory of operation Sample Clock Timebase The ADCs and DACs require an oversample clock to drive the conversion The oversample clock frequency is greater than the sample rate The oversample clock is produced from the sample clock timebase an even higher frequency signal The timing information for all ADCs and DACs comes from the common sample clock timebase signal You can share the sample clock timebase among synchronized devices Refer to the Master Sample Clock Timebase Synchronization section of this chapter for more information ei Note USB devices do not support synchronization A DDS chip produces the sample clock timebase DDS is a method of generating a programmable clock with excellent frequency resolution The DDS chip is capable of 32 bi
51. e Hardware siz csi iiccsatetetcasaed cca ee deed EE Woks Sk E ded badness Eed 1 1 Ree 1 1 Measurement System Overview cceceeceseeeesecesceseseeeeseeesecseeeaeeseeeaeeseeeaecseseasenseaes 1 2 Sensors and Transducers ensnare ces EENS EES dees sees 1 2 Chapter 2 Dynamic Signal Acquisition Device Concepts Nyquist Frequency and Nyquist Bandhwidth ee eeseescesseceseeeeeeceeeeeeeceaeeeseeeeaeeesees 2 1 Te 2 1 Analog Inputs ee a vedantic E 2 2 Analog Input Channel Confeuratons cic eceeeeseeseceeeeseeeseeeeneeeseenees 2 2 Choosing Channel Configurations 0 0 0 cc ceeeeeeeeeseeseeeseteeeeseeeees 2 2 Input Coupling csee a Ses wea Nea tated tee alee el 2 3 TEDS Transducer Electronic Data Sheet 2 4 TEP Rie eg is feet E E anes eae ese sted avn ave ee 2 5 Overload Detect Others ee e Eeer EE et 2 6 ADC i Eeer tell ai eta Ra oat A A ET 2 8 National Instruments Corporation v NI Dynamic Signal Acquisition User Manual Contents Analog Input Filters ekoi merreni a a AAR ANTARA Di 2 8 Ant Alltag Pultersi sinirinin inia 2 8 Supported DSA Devices icies s a a 2 11 Filter Delay ironiis EE E E aed a 2 11 FIFO and PCI Data Transfer 2 12 Analog Output NI USB 4431 and NI 4461 Only 2 12 QUtpUt DiStOrta On sex ie SEENEN Eege 2 12 Analog Output Channel Configurations 00 0 cece eeeceseeseeeseceeceeeteeeeseeeees 2 12 Choosing Channel Configurations cece eeeeseseeeereeseeenees 2 13 Output Impedance i c 24 56sccezc sessededsapas
52. e between positive and negative signal legs is approximately 22 Q when you generate a waveform When you are not generating a waveform configure the AO IdleOutputBehavior property for one of the following three idle behavior options Table 2 4 Output Impedence Output Impedance Idle Behavior Option Differential Mode Only Maintain Existing Value 22 Q Zero Volts 22 Q High Impedance 9 KQ DAC The delta sigma DACs on the NI 4461 function in a way analogous to delta sigma ADCs The digital data first passes through a digital interpolation filter then to the DAC resampling filter and finally to the delta sigma modulator In the DAC the delta sigma modulator converts high resolution digital data to high rate 1 bit digital data As in the ADC the modulator frequency shapes the quantization noise so that almost all of the quantization noise energy is above the Nyquist frequency The digital 1 bit data is then passed to an inherently linear 1 bit DAC The output of the DAC includes quantization noise at higher frequencies and some images still remain near multiples of eight times the effective sample rate NI Dynamic Signal Acquisition User Manual 2 14 ni com Chapter 2 Dynamic Signal Acquisition Device Concepts Analog Output Filters This section contains information about analog output filters Anti Imaging and Interpolation Filters A sampled signal repeats itself throughout the frequency spectrum a
53. e calibration certificate for your product at ni com calibration If you searched ni com and could not find the answers you need contact your local office or NI corporate headquarters Phone numbers for our worldwide offices are listed at the front of this manual You also can visit the Worldwide Offices section of ni com niglobal to access the branch office Web sites which provide up to date contact information support phone numbers email addresses and current events NI Dynamic Signal Acquisition User Manual B 2 ni com Glossary Symbols H lA IV A AC AC coupling ADC ADC resolution National Instruments Corporation Percent Positive of or plus Negative of or minus Plus or minus Less than Greater than Less than or equal to Greater than or equal to Per Degree Ohm Amperes Alternating current Allowing the transmission of AC signals while blocking DC signals A D converter an electronic device often an integrated circuit that converts an analog voltage to a digital number The size of the discrete steps in the ADCs input to output transfer function therefore the smallest voltage difference an ADC can discriminate with a single measurement NI Dynamic Signal Acquisition User Manual Glossary ADE Al alias amplification amplifier amplify amplitude flatness AO API asynchronous attenuate bandwidth bipolar Application dev
54. e input range over which a circuit can handle a common mode signal The mathematical average voltage relative to the computer s ground of the signals from a differential input A circuit that counts external pulses or clock pulses timing NI Dynamic Signal Acquisition User Manual Glossary coupling crosstalk current sourcing D DAC DAQ dB dBFS DC DC coupling DDS clock delta sigma modulating ADC device differential input differential measurement system digital trigger The manner in which a signal is connected from one location to another An unwanted signal on one channel due to an input on a different channel The ability of a device to supply current for analog or digital output signals D A converter an electronic device often an integrated circuit that converts a digital number into a corresponding analog voltage or current Data acquisition 1 Acquiring and measuring analog or digital electrical signals from sensors transducers and test probes or fixtures 2 Generating analog or digital electrical signals Decibel the unit for expressing a logarithmic measure of the ratio of two signal levels dB 20log10 V1 V2 for signals in volts Absolute signal level compared to full scale Direct current Allowing the transmission of both AC and DC signals Direct digital synthesis clock a type of clock source with an output frequency controlled by a digital tuning word
55. eference clock synchronization master and slave devices lock their ADC or DAC over the sample clock to the shared 10 MHz reference clock on the PXI and PXIe chassis backplane PXI_CLK10 The chassis supplies the clock independently to each peripheral slot An independent buffer drives the clock signal to each peripheral slot DSA devices that can synchronize with this method have phase locked loop PLL circuitry that allows them to lock to the reference clock You can drive PXI_CLK10 from NI Dynamic Signal Acquisition User Manual 2 24 ni com Chapter 2 Dynamic Signal Acquisition Device Concepts an external source through the PXI_CLK_IN pin on the P2 connector of the star trigger slot on the chassis Driving an external clock source on this pin automatically disables the 10 MHz source generated on the PXI backplane You can place the master and slave devices in any slot You also can synchronize all devices in the chassis After you install the DSA devices in the chassis complete the following steps to synchronize the hardware 1 Specify PXI_CLK10 as the reference clock source for all devices to force the DSA devices to lock to the reference clock on the PXI chassis Choose an arbitrary master board to issue a synch pulse on one of the PXI Trigger lines The sync pulse resets the ADCs and DACs and also resets the divide counter to phase align all the clocks in the system to within nanoseconds Start acquiring data on all DSA devices
56. elerometers for measuring linear acceleration or vibration Refer to Chapter 2 Dynamic Signal Acquisition Device Concepts for more information about typical DSA device measurements You also can refer to the NI DAQmx Help or the LabVIEW Help for more information about microphones or accelerometers NI Dynamic Signal Acquisition User Manual 1 2 ni com Dynamic Signal Acquisition Device Concepts This chapter contains information about Dynamic Signal Acquisition DSA device concepts including Nyquist frequency and bandwidth noise analog input and output timing and triggering and synchronization Nyquist Frequency and Nyquist Bandwidth Noise Any sampling system such as an ADC is limited in the bandwidth of the signals it can measure Specifically a sampling rate of f can represent only signals with frequencies lower than f 2 This maximum frequency is known as the Nyquist frequency The bandwidth from 0 Hz to the Nyquist frequency is the Nyquist bandwidth Caution Electromagnetic interference can adversely affect the measurement accuracy of the DSA products described in this document The inputs and outputs of these products are isolated from chassis ground for functional reasons Therefore the outer conductor of any connected coaxial cable is not connected to chassis ground and the outer conductor will not act as a shield for unwanted noise The shield can act as an antenna to transmit noise into the environment or re
57. elopment environment an application designed to make it easier for you to develop software Usually ADEs have a graphical user interface and programming tools to help with development Examples of ADEs are LabVIEW LabWindows CVI Visual Basic and Visual C Analog input A false lower frequency component that appears in sampled data acquired at too low a sampling rate The process of increasing signal amplitude using electronic components A signal with increased amplitude may allow improved measurement accuracy by using more ADC range and reducing analog signal noise prior to digitization An electronic component that increases analog signal amplitude See also amplification To increase signal amplitude using electronic components See also amplification A measure of how close to constant the gain of a circuit remains over a range of frequencies Analog output Application programming interface Hardware a property of an event that occurs at an arbitrary time without synchronization to a reference clock Software a property of a function that begins an operation and returns prior to the completion or termination of the operation To decrease the amplitude of a signal The range of frequencies present in a signal or the range of frequencies to which a measuring device can respond A signal range that includes both positive and negative values for example 5 V to 5 V NI Dynamic Signal Acquisition User Manua
58. en connected to a test object Operation of this hardware in a residential area is likely to cause harmful interference Users are required to correct the interference at their expense or cease operation of the hardware Changes or modifications not expressly approved by National Instruments may void the authority of the user to operate the hardware under the local regulatory rules The Declaration of Conformity DoC contains important supplementary EMC compliance information and instructions for the user or installer To obtain the DoC for this product visit ni com cert ification search by model number or product line and click the appropriate link in the Certification column Contents About This Manual Ier Te EE ix Related Documentation iensor ariii ri E EEE A D NEDA Q EE xi NI DAQmx for Luz xi LabVIEW EE xii LabWindows CVI pis eneen SEENEN a xiii Me s rement St diOs s iiinis i E ENEE R RE xiii ANSI C without NI Application Software e seeseseesseessseerssreresesesressresresrse xiv NET Languages without NI Application Software xiv Device Documentation and Specifications ee eeeeeceessceeeeeeeeeeseeeeeeaee xiv Training Cours S eneen cstsi ett a ERER NEA E A XV Technical Support on the Web A XV Chapter 1 Getting Started Tnistallin NEDA Q ra n iia tege ges ee SC dee Die ed Ee 1 1 Installing Other Software sccscesscescassecistacesesesseoesteecbaecasevehaeeouestaaascastaesusted ENEE 1 1 Installing th
59. eneration Application samples DAQmx Analog Out Generate Voltage Cont Gen Volt Wfm Int Clk Synchronization Applications This section contains information about developing synchronization applications with DSA devices ei Note USB devices do not support synchronization Synchronization Application Overview Due to the many synchronization configurations possible there is no way to present a general overview of how to construct a synchronization application It is important to know the theory behind the configurations NI Dynamic Signal Acquisition User Manual 3 8 ni com Chapter 3 Developing Your Dynamic Signal Acquisition Application signals involved and any applicable rules when constructing a synchronization application Refer to Chapter 2 Dynamic Signal Acquisition Device Concepts for more information about synchronization theory Use the synchronization examples to help you get started with your synchronization application Refer to the NI DA Qmx Help or the LabVIEW Help for more information about software steps necessary for synchronizing DSA devices Synchronization Application Examples NI DAQmx and all NI ADEs ship with examples you can use to get started with your application LabVIEW Examples The following LabVIEW examples illustrate synchronized analog input and output applications e Example Analog Input Synchronization Application Multi Device Sync AI Shared Timebase amp Trig DSA VI located in labvi
60. er Manual Appendix A Device Specific Information NI 4462 Block Diagram Figure A 4 shows the NI 4462 block diagram ADCO Le gt l Digital aN ADC 1 rei ADC Gain Offset p Filtering and gt FIFO PCI g p gt Interface Correction Decimation Interface ADC 2 ei Timing and Triggering lt gt gt Controller PCI Bus Lal ADC 3 PXI Trigger Bus Digital Trigger PFIO DDS S Figure A 4 NI 4462 Block Diagram NI Dynamic Signal Acquisition User Manual A 6 ni com Appendix A Device Specific Information Connecting Signals to NI 446x Devices This section contains information about connecting signals to NI 446x devices NI 446x Front Panels Figure A 5 shows the NI PXI 4461 NI PCI 4461 NI PXI 4462 and NI PCI 4462 front panels NATIONAL NATIONAL INSTRUMENTS INSTRUMENTS NI PXI 4461 NI PXI 4462 24 Bit 204 8 kS s 24 Bit 204 8 kS s NI PCI 4461 NI PCI 4462 Alo AIO 11 I Al Alt AOO A01 AlI3 7 N A A A A A Prio Z el prio A ez LI e tO NI PXI 4461 NI PCI 4461 NI PXI 4462 NI PCI 4462 Figure A 5 NI 446x Front Panels National Instruments Corporation A 7
61. est range setting above the peak level you expect to measure to provide sufficient headroom In applications where distortion performance is critical you can sacrifice overall dynamic range to improve distortion performance by selecting the 10 Vpk setting Refer to the NI 446x Specifications for distortion specifications for each gain setting The ADC is the most significant source of measurement noise until you use the 20 dB or 30 dB gain settings At these higher gain settings the analog front end circuitry becomes the dominant noise source To achieve the best absolute noise performance select the highest gain setting appropriate for your application NI Dynamic Signal Acquisition User Manual A 4 ni com Appendix A Device Specific Information NI 446x Block Diagrams This section contains the NI 446x block diagrams NI 4461 Block Diagram Figure A 3 shows the NI 4461 block diagram ADC 0 oe ADC Gaim Offset peata te rro Lei PO Le Interface Correction Mering an Interface Decimation _ f 2s Timing and 2 Triggering Tab 2 m a Controller 5 Q D j 8 Yy Yy x DAC 0 DAC La Gain Offset q Interpolation q FIFO DDS Interface Correction Filter DAC 1 Digital Trigger PFIO Figure A 3 NI 4461 Block Diagram National Instruments Corporation A 5 NI Dynamic Signal Acquisition Us
62. evices when you synchronize DSA devices that do not support low frequency alias rejection Inherent delays exist between different between families of DSA boards You might need to compensate for group delay in the waveforms when you synchronize between device families At very low sample rates you might notice that it takes several seconds for an acquisition to begin This is because during the sync pulse the ADCs get reset and have to wait many samples before delta sigmas are operational That time is dependant on the sample rate To improve the time it takes an acquisition to begin select a higher sample rate or enable low frequency alias rejection if possible on all boards This causes the ADC to run at a higher sample rate while the onboard firmware decimates the data back to your low sample rate For configurations that specify multiple sample rates between different devices the slave devices must be a power of two and slower than the master device sharing the clock For example if the master device has a sample rate of 100 kS s the slave devices can run at 50 kS s or 25 kS s but not at 40 kS s or 200 kS s The slowest sample rate device in the system must export the start trigger Because the delta sigmas run at different rates you have different group delays among all devices running at different rates 2 27 NI Dynamic Signal Acquisition User Manual Developing Your Dynamic Signal Acquisition Application This chapter con
63. ew examples DAQmx Synchronization Multi Device 1lb e Example Analog Output Synchronization Application Multi Device Sync AI and AO Shared Timebase amp Trig DSA VI located in labview examples DAQmx Synchronization Multi Device 1llb LabWindows CVI Example The following LabWindows CVI example in the CVI folder illustrates a synchronized DSA analog input application Example Analog Input Application samples DAQmx Synchronization Multi Device AI Shared Timebase amp Trig DSA National Instruments Corporation 3 9 NI Dynamic Signal Acquisition User Manual Device Specific Information This appendix contains information about specific National Instruments Dynamic Signal Acquisition DSA devices 3 Note Refer to ni com manuals for documentation for devices not listed here NI 446x Devices This section contains information about the NI 446x devices NI 446x Features The NI 446x devices are high performance high accuracy analog devices for PCI and PXI The NI 4461 devices feature two analog input and two analog output channels with gain and attenuation The NI 4462 features four analog input channels Refer to Chapter 2 Dynamic Signal Acquisition Device Concepts for more information about analog input analog output gain attenuation and other feature concepts NI 446x Analog Input Features Figure A 1 shows the NI 446x analog input circuitry block diagram National Instruments Corporation A 1 NI Dynam
64. ic Signal Acquisition User Manual Appendix A Device Specific Information 24 V Compliant IEPE Constant Current Source 4 10 mA 20 dB DC AC Coupling Be Analog Lowpass A D Filter Converter e ee Differential Amplifier Calibration Multiplexer Gain 0 dB AIX i g EE Gain 10 dB E or i H Gain 20 dB SE 1 ee Gain 30 dB i Gain 0 dB Gain 20 dB 50 Q CHSGND Figure A 1 NI 446x Analog Input Block Diagram The NI 446x input channels feature the following e Sampling rates up to 204 8 kS s e Per channel selection of six input voltage ranges from 0 316 V to 42 4 V pk e Per channel differential and pseudodifferential channel configuration e Per channel AC or DC coupling e Per channel IEPE current excitation e Pre digitization and post digitization overload detection e Anti alias filtering e Multiple triggering modes including external digital triggering NI Dynamic Signal Acquisition User Manual A 2 ni com Appendix A Device Specific Information NI 4461 Analog Output Features Figure A 2 shows the NI 4461 analog output circuitry block diagram Balanced D A Differential Converter Attenuator Driver 11Q AOXOUT AOXOUT Gain 0 dB Gain 20 dB Gain 40 dB AOGND J Gain dB 50 Q CHSGND Figure A 2 NI 4461 AO Block Diagram The NI 4461 outpu
65. ic Signal Acquisition User Manual Chapter 2 Dynamic Signal Acquisition Device Concepts Triggering Sharing the Sample Clock Timebase When you synchronize two or more DSA devices they must share a common sample clock timebase Each device uses the sample clock timebase to generate input and output sample clocks This common signal passes along the PXI_Star RTSI trigger bus You can program the master device to export the internally generated sample clock timebase to slave devices You must configure the slave devices to import the sample clock timebase Programming multiple DSA devices to share a common sample clock timebase provides tight synchronization and eliminates clock drift between devices The ratio between the sample rate f and sample clock timebase rate al can have one of several values Refer to the NI 446x Specifications NI 447x Specifications or NI 449x Specifications for more information This section contains information about triggering theory of operation Digital Triggering You can configure DSA devices to start an acquisition in response to a digital trigger signal on the PFI 0 connector located on the device front panel This pin is labeled EXT TRIG on NI 447x devices and it is labeled PFIO on NI 446x and NI 449x devices The trigger circuit can respond either to arising or a falling edge The trigger signal must comply to TTL voltage levels Refer to the NJ UBS 443x Specifications NI 446x Specifications
66. iples of that oversample rate fall below the cut off frequency of the analog anti aliasing filter If the signal contains energy near these frequencies aliasing can result You can prevent aliasing by raising the sample rate so that the first 128 f multiple falls above the cut off frequency of the analog anti aliasing filter For example a sample rate of 25 6 kS s is not subject to aliasing because the first 128 f multiple 3 2 MHz is well above the analog anti aliasing filter cut off frequency You can also enable low frequency alias rejection with the AI EnhancedAliasRejectionEnable property This property causes the DSA device to automatically oversample for sample rates between 1 kS s and 25 6 kS s The resulting oversampled rate always falls in the 25 6 kS s to 51 2 kS s range The data stream is then decimated down by the same multiple to produce samples at the specified sample rate Table 2 2 lists the decimation factors for given sample rates Refer to the NI DAQm x Help or the LabVIEW Help for more information about the AILEnhancedAliasRejectionEnable property Table 2 2 Decimation Factors for Given Sample Rates Sample Rate Decimation Factor 100 S s lt f 200 S s 256 200 S s lt f lt 400 S s 128 400 S s lt f lt 800 S s 64 800 S s lt f lt 1 6 kS s 32 1 6 kS s lt fs lt 3 2 kS s 16 3 2 kS s lt fs lt 6 4 kS s 8 NI Dynamic Signal Acquisition User Manual 2 10 ni com Chapter
67. ix A Device Specific Information NI 447x Analog Input Features Figure A 14 shows the NI 447x analog input circuitry block diagram 24 V Compliant IEPE Constant Current Source 4mA IEPE Common Mode H On Off DC AC SE Couplin gt Choke checks SE Differential Analog CHO e DAMS i i i Buffer Lowpass 1 i Filter E eg i eg A D K Converter 0 01 HF S Calibration F Multiplexer RP Gain 12 77 dB 50 Q S77 ae 0 01 pF V NI Dynamic Signal Acquisition User Manual The Figure A 14 NI 447x Analog Block Diagram NI 447x analog input channels feature the following Simultaneous sampling at up to 102 4 kS s Per channel AC or DC coupling Per channel IEPE current excitation Anti alias filtering Postdigitization digital overload detection Multiple triggering modes including external digital triggering A 14 ni com Appendix A Device Specific Information NI 447x Digital Function Block Diagram Figure A 15 shows the NI 447x digital function block diagram MiniMITE Al FIFO PCI Controller i Synchronization DMA Control PCI Bus General Control Clock Control To ADCs DDS Clock Generator Figure A 15 NI 447x Digital Function Block Diagram National Instruments Corporation A 15 NI Dynamic Signal Acquisition User Manual Appendix A Device Specific Information Connecting
68. ize the time required for 38 5 update clock cycles to elapse The interpolation filter adds additional output filter delay depending on the update rate Table 2 5 provides more information on how the interpolation filter affects the output filter delay Table 2 5 Interpolation Factor and Output Filter Delay NI 4461 Output NI USB 4431 Output Update Rate Interpolation Filter Delay Filter Delay kS s Factor Samples Samples 10 lt f lt 1 6 128 36 6 63 3 16 lt f lt 3 2 64 36 8 62 6 3 2 lt f lt 6 4 32 37 4 61 3 6 4 lt f lt 12 8 16 38 5 58 5 12 8 lt fs lt 25 6 8 40 8 53 25 6 lt f lt 51 2 4 43 2 42 51 2 lt f lt 102 4 2 48 0 20 102 4 lt fs lt 204 8 1 32 0 Not Supported National Instruments Corporation 2 17 NI Dynamic Signal Acquisition User Manual Chapter 2 Dynamic Signal Acquisition Device Concepts FIFO and PCI Data Transfer 3 DSA device input channels share a FIFO buffer and the output channels share a separate FIFO buffer The NI USB 4431 and NI 446x Specifications contain information about the buffer sample depth The NI 4461 has a flexible data transfer request condition You can program the device to request DMA transfers according to a user programmable FIFO condition Refer to the NI DAQmx Help or the LabVIEW Help for information about conditions available for specific devices Note USB devices do not support setting the transfer request
69. l G 2 ni com BNC buffer burst DMA transfer bus Butterworth filter C C CCIF channel clipping clock CMRR code width common mode range common mode signal counter timer National Instruments Corporation G 3 Glossary Bayonet Neill Concelman a type of coaxial connector used in situations that require shielded cable for signal connections and or controlled impedance applications Software temporary storage for acquired or generated data A DMA transfer in which one sample of data transfers to memory every bus clock period The group of conductors that interconnect individual circuitry in a computer Typically a bus is the expansion vehicle to which I O or other devices are connected Examples of PC buses are the ISA and PCI bus A filter with a smooth response over all frequencies and a monotonic decrease from the specified cut off frequency Celsius See IMD Pin or wire lead used to acquire or generate an analog or digital signal Analog channels can be single ended or differential Clipping occurs when an input signal exceeds the input range of the amplifier and results in an overload condition Digital signal that controls timing common mode rejection ratio a measure of the ability of an instrument to reject interference from a common mode signal usually expressed in decibels dB The smallest detectable change in an input voltage of a device See also ADC resolution Th
70. l trigger appear to occur earlier than expected The acquired buffer appears to begin earlier than expected because of some triggering and filter delay relationships Refer to the NJ USB 443x Specifications NI 446x Specifications NI 447x Specifications and NI 449x Specifications for information about filter delay for each device National Instruments Corporation 2 11 NI Dynamic Signal Acquisition User Manual Chapter 2 Dynamic Signal Acquisition Device Concepts FIFO and PCI Data Transfer DSA device input channels share a FIFO buffer and the output channels share a separate FIFO buffer The NJ USB 443x Specifications NI 446x Specifications NI 447x Specifications and NI 449x Specifications contain information about the buffer sample depth The devices have a flexible data transfer request condition You can program the device to request DMA transfers according to a user programmable FIFO condition Refer to the NJ DAQmx Help or the LabVIEW Help for information about conditions available for specific devices ei Note USB devices do not allow setting the transfer request condition Analog Output NI USB 4431 and NI 4461 Only Output Distortion This section contains information about analog output concepts You can minimize output distortion by connecting the outputs to external devices with a high input impedance Each output channel of the NI 4461 is rated to drive a minimal load of 600 Q Each output channel of the NI 4
71. log input applications e Example Acceleration Application samples DAQmx Analog In Measure Acceleration Cont Accel Samps Int Clk Anlg Start e Example Sound Pressure Application samples DAQmx Analog In Measure Sound Pressure Cont Acq Snd Press Samps Int Clk Analog Output Applications NI USB 4431 and NI 4461 Only This section contains information about developing analog output applications with DSA devices Analog Output Application Overview This section presents some general overview information about creating an analog output application using NI DAQmx and LabVIEW or LabWindows CVI National Instruments Corporation 3 5 NI Dynamic Signal Acquisition User Manual Chapter 3 Developing Your Dynamic Signal Acquisition Application Figure 3 2 shows a typical flowchart for programming an analog output task generating a waveform and clearing the task No Create Task Yes Programmatically y Create a Task Programmatically Create Task and Channels y in DAQ Assistant Create AO Channels y Configure Channels Optional y lt Specify Timing Specify Start Triggering Optional d er Synthesize Data Write Write More Samples Start Synthesize Data y Write Clear a Figure 3 2 NI 4461 Analog Output Task Flowchart NI Dynamic Signal Acquisition User Manual 3 6 ni com
72. ly 4 6 kHz 0 46 f it passes through the digital filter At 4 86 kHz the digital filter applies 3 dB attenuation The digital filter provides at least 110 dB of attenuation for frequency components above the Nyquist frequency However the digital filter can potentially admit aliases in the much higher frequency range from 1 275 MHz to 1 285 MHz 128 f the example sample rate of 10 kS s If noise in the input signal falls into this narrow window the noise is not rejected by the digital filter In this limited frequency range you must consider the response of the analog filter Figure A 20 illustrates that with a sampling rate of 10 kS s the analog filter attenuates an input signal frequency of 1 28 MHz by 40 dB National Instruments Corporation A 19 NI Dynamic Signal Acquisition User Manual Appendix A Device Specific Information On NI 447x devices with low frequency alias rejection enabled the sawtooth line in Figure A 20 represents the filter response The worst case alias rejection is approximately 63 dB This corresponds to the analog filter attenuation at 25 6 kS s Alias Rejection dB 0 00 10 00 20 00 30 00 40 00 50 00 60 00 70 00 80 00 90 00 100 00 Sample Rate kS s 1 0 10 0 Oversample 128 kHz 1 28 MHz Frequency 1286 64h 100 0 200 0 6 4 MHz Figure A 20 NI 447x Anal
73. modes 2 21 National Instruments support and services B 1 NET languages documentation xiv NI 4461 A 5 NI 446x A 1 A 5 A 7 A 10 NI 446x input A 8 NI Dynamic Signal Acquisition User Manual NI 446x output A 9 NI 447x A 13 A 16 A 18 NI 447x input A 17 NI 449x A 21 A 22 A 25 NI support and services B 1 noise 2 1 2 2 nyquist bandwidth 2 1 nyquist frequency 2 1 0 output NI PXI 4461 only 2 12 2 17 2 18 output distortion 2 12 output impedance NI PXI 4461 only 2 14 overload detection 2 6 oversample clock 2 19 P PCI data transfer FIFO and 2 12 2 18 PLL A 13 A 26 power off and power loss 2 18 programming examples NI resources B 1 PXI_CLK10 2 24 R reference clock 2 24 rejection low frequency alias 2 10 related documentation x S sample clock timebase 2 19 sharing the sample clock timebase 2 20 smart sensor 2 4 software NI resources B 1 support technical B 1 synchronization 2 24 3 8 3 9 synchronization programming 3 8 ni com Index T W technical support B 1 Web resources B 1 TEDS 2 4 window triggering 2 22 timing 2 19 training and certification NI resources B 1 transducer electronic data sheet 2 4 triggering 2 19 triggering and filter delay 2 23 troubleshooting NI resources B 1 National Instruments Corporation l 3 NI Dynamic Signal Acquisition User Manual
74. nal Services Glossary Index NI Dynamic Signal Acquisition User Manual viji ni com About This Manual Conventions This manual contains information about using National Instruments Dynamic Signal Acquisition DSA devices These devices have 24 bit resolution and support sample rates of up to 204 8 kS s With excellent dynamic range noise and distortion performance and simultaneous sampling and synchronization capabilities the DSA devices discussed in this help file are well suited for many applications including but not limited to e Audio testing e Acoustic measurements e Environmental noise testing e Vibration analysis e Noise vibration and harshness measurements e Machine condition monitoring e Rotating machinery evaluation If you have not already installed the device refer to the DAQ Getting Started Guide This manual does not describe how to use the USB 923x cRIO 923x or cRIO 4408 devices For information about these devices go to ni com manuals To comment on National Instruments documentation refer to the National Instruments Web site at ni com lt gt The following conventions are used in this manual Angle brackets that contain numbers separated by an ellipsis represent a range of values associated with a bit or signal name for example AO lt 3 0 gt The symbol leads you through nested menu items and dialog box options to a final action The sequence File Page Set
75. nalog overload point for DSA devices is approximately 10 7 Na the voltage at which the front end circuitry begins showing signs of saturation Figure 2 1 shows harmonic aliases caused by clipping with a 1 0 kHz sine wave at 10 8 Vu versus the same signal at 8 9 V kx which shows no clipping on an NI 446x device NI USB 443x NI 447x and NI 449x devices display similar behavior NI Dynamic Signal Acquisition User Manual 2 6 ni com Chapter 2 Dynamic Signal Acquisition Device Concepts 10 0 4 20 a Ee EES Ee i Ee ed Ee E EE ET ES E SE es eee Bea DH DER EE ECH EES T S Sg EES oS EE 60 Se EE green ttt 5 80 H E o TIT 2 BEER 110 j FIP 120 130 140 el ee se ees 150 Ke EE E 10k 20k 30k 40k 50k 60k 70k 80k 90k 200k 110k Frequency Hz 0 10 20 30 40 50 2 60 Ve 70 80 GC 90 8 100 110 H 120 130 140 150 160 a ka f 0 5k 10k 15k 20k 25k 30k 35k 40k 45k 50k 55k Frequency Hz Figure 2 1 NI 446x Harmonic Aliases UN Caution For NI 446x devices overload detection is not supported for the 42 4 Na input range setting This setting attenuates the signal by a factor of 10 This attenuation factor implies that the ADC reaches the analog saturation point at 115 Va This level is greater than what the 42 4 V pk range can safely support You risk damaging the input circuitry National Instruments Corporation 2 7 NI Dyn
76. ndicated in the DoC In special cases for example when either highly sensitive or noisy hardware is being used in close proximity to National Instruments hardware you may have to employ additional mitigation measures to minimize the potential for electromagnetic interference While this hardware is compliant with the applicable regulatory EMC requirements there is no guarantee that interference will not occur in a particular installation To minimize the potential for the hardware to cause interference to radio and television reception or to experience unacceptable performance degradation install and use this hardware in strict accordance with the instructions in the hardware documentation and the DoC If this hardware causes interference with licensed radio communications services or other nearby electronic hardware which you can determine by powering the hardware off and on you are encouraged to try to correct the interference by one or more of the following measures e Reorient the antenna of the receiver the device suffering interference e Relocate the transmitter the device generating interference with respect to the receiver e Plug the transmitter into a different outlet so that the transmitter and the receiver are on different branch circuits This hardware may generate emissions that exceed regulatory requirements or may become more sensitive to disturbances in the local electromagnetic environment when test leads are attached or wh
77. nge For AO if the DUT input is grounded use the differential channel configuration A grounded source or DUT is already connected to a ground reference point with respect to the device if the PXI or CompactPCI chassis and controller are plugged into the same power system Provide only one ground reference point for each channel by properly selecting differential or pseudodifferential configuration If you provide two ground reference points for example if you select pseudodifferential mode with a grounded accelerometer or amplifier the difference in ground potential results in currents in the ground system that can cause measurement errors The 50 Q or 1 KQ resistor on the signal ground is usually sufficient to reduce this current to negligible levels but results can vary depending on the system setup Configure the channels based on the signal source reference or DUT configuration Refer to Table 2 3 to determine how to configure the channel Table 2 3 Analog Output DUT Input Reference Channel Configuration Floating Pseudodifferential Grounded Differential The NI 446x is automatically configured for differential mode when powered on or powered off This configuration protects the 50 Q resistor on the negative pin National Instruments Corporation 2 13 NI Dynamic Signal Acquisition User Manual Chapter 2 Dynamic Signal Acquisition Device Concepts Output Impedance The differential output impedanc
78. og Filter Response This situation represents the set of worst case alias rejections for each sample rate You would only observe this worst case scenario with a well defined tone in a narrow frequency range In real measurement situations it is more likely that any energy passing the digital filter consists only of low amplitude noise If an unwanted component does appear in the digitized signal increasing the sampling rate might provide an easy solution by both improving the rejection from the analog filter and by repositioning the digital filter so that it can eliminate the alias Under most circumstances use the first figure to calculate the NI 447x alias rejection NI 447x Specifications Refer to the NI 447x Specifications for more detailed information about the NI 447x devices NI Dynamic Signal Acquisition User Manual A 20 ni com Appendix A Device Specific Information NI 449x Devices This section contains information about the NI 449x devices NI 449x Features The NI 449x devices are high performance high accuracy analog input devices for PXI or PXIe The NI 4498 and 4496 devices feature 16 AC coupled inputs with IEPE and TEDS capability The NI 4498 features four input ranges of 0 316 V 1 V 3 16 V and 10 V The NI 4496 has two input ranges of 3 16 V and 10 V Refer to Chapter 2 Dynamic Signal Acquisition Device Concepts for more information about analog input and other feature concepts NI 449x Analog Input
79. ottom of the front face of the module If you use a PCI device keep the screw that held the PCI slot cover to the computer chassis Reinsert this screw to securely attach the device Choosing Channel Configurations If the signal source or DUT inputs are floating use the pseudodifferential configuration You must provide a ground reference for a floating signal If you do not provide a ground reference point for example selecting NI Dynamic Signal Acquisition User Manual 2 2 ni com Chapter 2 Dynamic Signal Acquisition Device Concepts differential mode with a floating microphone or shaker table input amplifier with differential inputs the outputs or inputs can drift outside the device common mode range For AI if the signal source is grounded use either the differential or pseudodifferential configurations Provide only one ground reference point for each channel by properly selecting differential or pseudodifferential configuration If you provide two ground reference points for example if you select pseudodifferential mode with a grounded accelerometer or amplifier the difference in ground potential results in currents in the ground system that can cause measurement errors The 50 Q and 1 KQ resistor on the signal ground is usually sufficient to reduce this current to negligible levels but results can vary depending on the system setup Configure the channels based on the signal source reference or DUT configuration Refer to
80. rated In the case of AO a FIFO permits faster update rates because the waveform data can be stored on the FIFO ahead of time Faster update rates again reduce the effect of latencies associated with getting the data from system memory to the device The time required for data to propagate through a converter A type of signal conditioning that allows you to attenuate unwanted portions of the signal you are trying to measure resulting in a signal with less noise and unwanted components Input signal frequency Finite impulse response a non recursive digital filter with linear phase Signal sources with voltage signals that are not connected to an absolute reference or system ground Also called nonreferenced signal sources Some common examples of floating signal sources are batteries transformers or thermocouples Sampling frequency or rate The factor by which a signal is amplified sometimes expressed in decibels A signal source connected in some way to a ground reference either chassis or earth ground NI Dynamic Signal Acquisition User Manual G 6 ni com H h hardware hardware triggering harmonics high impedance hysteresis triggering TEPE images IMD in National Instruments Corporation G 7 Glossary Hours The physical components of a computer system such as the circuit boards plug in devices chassis enclosures peripherals and cables A form of triggering where you set the st
81. resreresresrrsesrrsrsresrse A 8 NI 4461 Output Connections sssssesssesssesessessrerrsrsrrsrsresrssesresrrersreerse A 9 NI446x Filter e A 10 NI PXI 446x Reference Clock Synchronization esssseeseseeseerseeerererreseseeses A 13 NEA46x Specifications E A 13 EE E RE e A 13 INVA Toc EE A 13 NI 447x Analog Input Features A 14 NI 447x Digital Function Block Diagram o oo eee eeeeeseeseeeeeeeeneeeaeeees A 15 Connecting Signals to NI 447x Devices eee eeceeseesceeneceeeeaeeeeeeseseeeeaees A 16 NI 447 x Front Panels sec ceccuedeivetsesshentet served dag voce te essed e a dente eds A 16 NI 447x Input Connections 0 0 eee eceessceeeseceeeseeeeeeeeeseeaeenseeaes A 17 KIEREN e A 18 NIE Specification Seins e dE a eae Eaa A RONE EEEE NAE A 20 EIERE EE A 21 NI 449x Features ent Egger A 21 NI 449x Analog Input Features eee eeeeseeeeeeseeneeeseseeensereees A 21 NI449 Block Diagram i 3 33 0 bette tannin Edge eee A 22 Connecting Signals to NI 449x Devices eee eee eeceeseeseeeseceeeeseeeeeeseseeeeaees A 22 NI 449x Front Panels ennenen ash dae Ee KE A 22 BNC Connector Polarity senesne i e a E E E RERA A 24 NI 449x Filter Response sis doritori ssia EeREEREEd sands apero aioa KETSE re K SEIE ia A 25 NI 449x Reference Clock Synchronization esesessseessseessesesrrsreresresesreseseeses A 26 NI449 Ee E A 26 National Instruments Corporation vii NI Dynamic Signal Acquisition User Manual Contents Appendix B Technical Support and Professio
82. s palettes menus and tools You also can refer to the following pages on ni com for more information Go to ni com info and enter the info code e Smart Sensors Info code rdsenr e What Are Plug amp Play Sensors Info code rdpnpy e IEEE 1451 4 Sensor Templates Overview Info code rdted6 IEPE If you attach an JEPE accelerometer or microphone to an AI channel that requires excitation from the DSA device you must enable the IEPE excitation circuitry for that channel to generate the required excitation current You can independently configure IEPE signal conditioning on a per channel basis on all DSA devices A DC voltage offset is generated equal to the product of the excitation current and sensor impedance when IEPE signal conditioning is enabled To remove the unwanted offset enable AC coupling Use DC coupling with IEPE excitation enabled only if the offset does not exceed the voltage range of the channel Common JEPE excitation values are 2 1 4 and 10 mA Refer to the NI USB 443x Specifications NI 446x Specifications NI 447x Specifications and NI 449x Specifications for a list of supported IEPE current values for each device National Instruments Corporation 2 5 NI Dynamic Signal Acquisition User Manual Chapter 2 Dynamic Signal Acquisition Device Concepts B Note You must set the NI 446x inputs in pseudodifferential mode when IEPE is turned on Overload Detection When the signal voltage exceeds the ADC range
83. s shown in Figure 2 2 This figure shows how the signal repetitions begin above one half the sample rate f and theoretically continue up through the spectrum to infinity Images remain in the sampled data because the data actually represents only the frequency components below one half f the baseband The device filters out the extra images in the signal in three stages Amplitude Baseband Signal Images A N e e e Perr ren Ee a ae a a Le Co Se Gas TE EE EE Gd TTT gt fs 8 fs 32 f 64 fs Frequency Figure 2 2 Sampled Signal First the data is digitally interpolated at 2 times f where n is a positive integer from 0 to 7 The interpolation factor must be sufficient to move the resulting effective sample rate f into the 102 4 kS s or higher range Figure 2 3 shows an example of four times interpolation and the resulting images A linear phase digital filter then removes almost all energy above one half f Baseband Signal Images After the Digital Interpolation Filter F po 4 ut Figure 2 3 Signal After Digital Filter National Instruments Corporation 2 15 NI Dynamic Signal Acquisition User Manual Chapter 2 Dynamic Signal Acquisition Device Concepts Second the DAC resamples the data to a new frequency fp c The frequency fp c is eight times higher than f Figure 2 4 shows the resulting images oO 3 lt Baseband Signal
84. s transformers fluorescent lights soldering irons CRT displays computers electrical storms welders radio transmitters and internal sources such as semiconductors resistors and capacitors Noise corrupts signals you are trying to send or receive Signal sources with voltage signals that are not connected to an absolute reference or system ground Also called floating signal sources Some common example of nonreferenced signal sources are batteries transformers or thermocouples The bandwidth from 0 Hz to the Nyquist frequency A frequency that is one half the sampling rate See also Nyquist Sampling Theorem The theorem that states that if a continuous bandwidth limited analog signal contains no frequency components equal to or higher than half the frequency at which it is sampled then the original signal can be recovered without distortion A measurement level beyond the stated or selected range of a device Sampling at a rate higher than the Nyquist frequency The range of frequencies which a device can properly propagate or measure Peripheral component interconnect a high performance PC expansion bus architecture originally developed by Intel to replace ISA and EISA It offers a theoretical maximum transfer rate of 132 Mbytes s Programmable function input a signal line often used for timing triggering and synchronization NI Dynamic Signal Acquisition User Manual Glossary posttriggering pretriggering
85. s shared clock guarantees that all ADC and DAC clocks share the same frequency The signal is routed on PXI Star for PXI systems and any of the RTSI lines for PCI systems The default RTSI line is 8 2 Program the master device to route a sync pulse to all the slave boards For PXI systems you can use any of the PXI trigger lines to do this For PCI devices the default RTSI line is 9 but you can program another line The sync pulse first resets the ADCs and DACs in the entire system at the same time then phase aligns all the clocks on the board to within nanoseconds 3 Start acquiring on all boards simultaneously Force one device to export its start trigger on one of the PXI trigger lines for a PXI system or one of the RTSI lines 0 to 6 for a PCI system The device does not have to be the master to send the start trigger Any device in the test system now can begin the acquisition NI Dynamic Signal Acquisition User Manual 2 26 ni com Chapter 2 Dynamic Signal Acquisition Device Concepts Consider the following caveats to using Master Sample Timebase synchronization National Instruments Corporation Not all DSA devices support low frequency alias rejection When you synchronize multiple DSA devices you must verify that all the devices share the same low frequency alias rejection setting You can enable low frequency alias rejection if all of the DSA devices in the system support it Disable low frequency alias rejection on all d
86. s to NI Applications Engineers via phone and email for one to one technical support as well as exclusive access to on demand training modules via the Services Resource Center NI offers complementary membership for a full year after purchase after which you may renew to continue your benefits For information about other technical support options in your area visit ni com services or contact your local office at ni com contact Training and Certification Visit ni com training for self paced training eLearning virtual classrooms interactive CDs and Certification program information You also can register for instructor led hands on courses at locations around the world System Integration If you have time constraints limited in house technical resources or other project challenges National Instruments Alliance Partner members can help To learn more call your local NI office or visit ni com alliance B 1 NI Dynamic Signal Acquisition User Manual Appendix B Technical Support and Professional Services e Declaration of Conformity DoC A DoC is our claim of compliance with the Council of the European Communities using the manufacturer s declaration of conformity This system affords the user protection for electromagnetic compatibility EMC and product safety You can obtain the DoC for your product by visiting ni com certification e Calibration Certificate If your product supports calibration you can obtain th
87. simultaneously Force one DSA device to export the start trigger on one of the PXI Trigger lines for a PXI system The device does not have to be the master to send the start trigger Any device in the test system now can begin the acquisition Consider the following caveats to using Reference Clock synchronization National Instruments Corporation Not all DSA devices support low frequency alias rejection When you synchronize multiple DSA devices you must verify that all the devices share the same low frequency alias rejection setting You can enable low frequency alias rejection if all of the DSA devices in the system support it Disable low frequency alias rejection on all devices when at least one DSA devices does not support it Inherent delays exist between different families of DSA boards You might need to compensate for group delay in the waveforms when you synchronize between device families At very low sample rates you might notice that it takes several seconds for an acquisition to begin This is because during the sync pulse the ADCs get reset and have to wait many samples before delta sigmas are operational That time is dependant on the sample rate To improve the time it takes an acquisition to begin select a higher sample rate or enable low frequency alias rejection if possible on all boards This causes the ADC to run at a higher sample rate while the onboard firmware decimates the data back to your low sample rate
88. sing Create a task programmatically using the following VIs the following functions e DAQmx Create Task VI e DAQmxCreateTask e DAQmx Create Virtual Channel VI DAQmxCreateAIVoltageChan e DAQmx Timing VI e DAQmxCfgSampClkTiming e DAQmx Triggering VI s DAQmxAnlgEdgeStartTrig or e DAQmxCfgDigEdgeStartTrig Configure One or more channel property node s One or more calls to Channels DAQmxSetChanAttribute Start DAQmx Start Task VI DAQmxStartTask Measurement Read DAQmx Read VI DAQmxReadAnalog64 or other data Measurement reading function Analyze Data Common analysis tools include VIs Common analysis tools include the from the Sound and Vibration functions in the LabWindows CVI Measurement Suite or Waveform Advanced Analysis Library Measurement Functions Display Data Front panel graph chart or indicator Graphical User Interface GUI graph chart or indicator Continue Loop around DAQmx Read VI Loop around DAQmxReadAnalog64 or Sampling other data reading function Stop DAQm x Stop Task VI DAQmxStopTask Measurement National Instruments Corporation 3 3 NI Dynamic Signal Acquisition User Manual Chapter 3 Developing Your Dynamic Signal Acquisition Application Table 3 1 Analog Input Application Steps Continued Flowchart LabVIEW LabWindows CVI Step Step Step Clear Task DAQmx Clear Task VI DAQmxClearTask These steps might be optional depending on your application t Refer to the NJ
89. ss of the anti alias filtering Computer monitor noise for example typically occurs at frequencies between 15 kHz and 65 kHz If the signal of interest is restricted to below 10 kHz for example the anti alias filters reject the monitor noise outside the frequency band of interest and a sampling rate of at least 21 6 kS s guarantees that any signal components in the 10 kHz bandwidth of interest are acquired without aliasing and without being attenuated by the digital filter Refer to the Analog Input Filters section of this chapter for more information about anti alias filtering When possible use the differential configuration to minimize the effect of any noise produced by ground currents in the chassis and common mode noise If you have particularly noisy AC power consider external filtering such as a line conditioner or an uninterruptible power supply This section contains information about DSA device analog input concepts Analog Input Channel Configurations The NI 446x supports two terminal configurations for analog input differential and pseudodifferential The NI USB 443x NI 447x and NI 449x support only the pseudodifferential channel configuration The term pseudodifferential refers to the 50 Q and 1 kQ resistance between the outer connector shell and chassis ground 3 Note Attach all DSA devices to the chassis with screws to provide a reliable ground connection If you use a PXI device tighten the screws at the top and b
90. t channels feature the following e Update rates to 204 8 kS s e Per channel selection of three output voltage ranges from 10 V to 0 1 V e Per channel differential and pseudodifferential channel configuration e Anti image filtering e External digital triggering NI 446x Gain and Attenuation Positive gain values amplify the signal before the A D converter ADC digitizes it This signal amplification reduces the measurement range However amplifying the signal before digitization allows better resolution by strengthening weak signal components before they reach the ADC Conversely negative gains attenuate the signal before they reach the ADC This attenuation increases the effective measurement range though it sacrifices some resolution for weaker signal components Refer to Chapter 2 Dynamic Signal Acquisition Device Concepts for more information about ADCs i Note In this manual AI attenuation is referred to as gain with a negative value You can set attenuation directly in software by assigning a negative value to the AI Gain property Refer to the NJ DAQm x Help or the LabVIEW Help for more information National Instruments Corporation A 3 NI Dynamic Signal Acquisition User Manual Appendix A Device Specific Information The NI 446x has six available gain settings for each AI channel Each gain setting corresponds to a particular AI range and each range is centered on O V The gain settings are specified in decibels
91. t resolution and can produce 4 294 967 296 steps to create the sample clock timebase Refer to the NJ USB 443x Specifications NI 446x Specifications NI 447x Specifications and NI 449x Specifications for more information about device frequency resolution External Clock The sample clock timebase which drives the conversion on DSA devices has stringent requirements for frequency and stability DSA devices do not accept arbitrary clock signals from external sources such as encoders or tachometers However signal processing features in the Sound and Vibration Measurement Suite often provide an excellent alternative to external clocking in encoder and tachometer applications Visit ni com soundandvibration for more information about the Sound and Vibration Measurement Suite ei Note NI USB 4431 and NI 4461 You can run input and output operations simultaneously at different rates on the NI USB 4431 and NI 4461 However because the timing information for all operations is derived from a common sample clock timebase the ratios between input and output sample rates can differ only by a factor of 2 where n is an integer For example assume that the input sample rate is 8 kS s Valid output sample rates include but are not limited to 2 kS s 8 kS s 16 kS s and 64 kS s In this case 20 kS s is not a valid output sample rate because the ratio between 8 kS s and 20 kS s is not a power of 2 National Instruments Corporation 2 19 NI Dynam
92. tains information about developing applications with Dynamic Signal Acquisition DSA devices Creating a Task Using the DAQ Assistant Using the DAQ Assistant to create and configure a task allows you to save several programming steps in your application In addition you can save the task for use in future applications You can use tasks you create with the DAQ Assistant with any NI application software you use to control a DSA device You can launch the DAQ Assistant from any NI application software If you are programming in LabVIEW you can take advantage of the DAQ Assistant Express VI to further simplify your application The DAQ Assistant Express VI allows you to perform a complete analog input or analog output operation using a single VI on the LabVIEW block diagram The DAQ Assistant Express VI uses the DAQ Assistant to create and configure a task and also handles task execution Refer to the LabVIEW Help for more information about the DAQ Assistant Express VI Refer to your NI application software documentation for specific information about launching the DAQ Assistant Refer to the DAQ Assistant Help for more information about using the DAQ Assistant Analog Input Applications This section contains information about developing analog input applications with DSA devices Analog Input Application Overview This section presents some general overview information about creating an analog input application using NI DAQmx and
93. tart All Programs National Instruments NI DAQ NI DAQ Readme The NI DAQmx Help contains general information about measurement concepts key NI DAQmx concepts and common applications that are applicable to all programming environments Select Start All Programs National Instruments NI DA Q NI DAQm x Help The Traditional NI DAQ Legacy User Manual contains an API overview and general information about measurement concepts Select Start All Programs National Instruments NI DAQ Traditional NI DAQ Legacy User Manual The DAQ Assistant Help describes how to use the DAQ Assistant to interactively configure common measurement tasks global virtual channels or scales Select Help Help Topics NI DAQmx DAQ Assistant in the Measurement amp Automation Explorer window NI DAQmx for Linux The DAQ Getting Started Guide describes how to install your NI DAQmx supported DAQ device and confirm that your device is operating properly The NI DAQ Readme for Linux lists supported devices and includes software installation instructions frequently asked questions and known issues The C Function Reference Help describes functions and attributes National Instruments Corporation xi NI Dynamic Signal Acquisition User Manual About This Manual The NI DAQmx for Linux Configuration Guide provides configuration instructions templates and instructions for using test panels B Note All NI DAQmx documentation for Linux is installed
94. tasendashceuscste Soden seats setetserts E ia E E 2 14 DAG aerer oe EES EE EENS SEA 2 14 Analog Output Fleet soeone EEN EES 2 15 Anti Imaging and Interpolation Filters eee eeeeereeteee 2 15 Filter Delay icici ins hese ssacecwoassatac eas Ee ed dite 2 17 FIFO and PCI Data Transfer 2 18 Power Off and Power LOSS 2 sccecsssecisnechesseseaeesiveebvneessescsedecttcecbevtescapeteecsiaes 2 18 Taming and Trig Bering osni rooier rni i a E E sabes eovaesbeevdivdaasiysoapdeeyecuseys 2 19 Sample Clock Timebases cisions oaia e 2 19 Extemal Clock sissi ianen Sun n foo dinette abd ais tice eee 2 19 Sharing the Sample Clock Timebase AAA 2 20 Tmgeepng euer aa a ae E e Ee RE a EE E E aE 2 20 III RK 2 20 AMNAlOS TRS Sr deene e ane vance vas E 2 21 Triggering and Filter Delay 0 0 0 cece eeeeceeseceeeeeeeeeeseeeeeeeeneeenees 2 23 SYMCHLOMIZAULON EE 2 24 Reference Clock Synchronization PXI PXTe Only sesser 2 24 Master Sample Clock Timebase Svnchron zapen 2 26 Chapter 3 Developing Your Dynamic Signal Acquisition Application Creating a Task Using the DAQ Assistant 0 0 0 eceeeeseeseeeseeeceeeeseceseteesnseeseeseeeaees 3 1 Analog Input Applications eieiei geeegeek a E steve EOE 3 1 Analog Input Application Overview ee eeeecceseceseeseeeseeeeeseceeeesesseeeaeesees 3 1 Analog Input Application Examples A 3 4 LabVIEW Examples eege tie AE E 3 4 LabWindows CVI Examples A 3 5 Analog Output Applications NI USB 4431 and NI 4461 Only 0 3 5 An
95. the digitized signal increasing the sampling rate might provide an easy solution by both improving the rejection from the analog filter and by repositioning the digital filter so that it can eliminate the alias Under most circumstances use the first figure to calculate the NI 446x alias rejection NI Dynamic Signal Acquisition User Manual A 12 ni com Appendix A Device Specific Information NI PXI 446x Reference Clock Synchronization NI PXI 446x devices employ onboard PLL circuitry The PLL circuitry locks the onboard 100 MHz voltage controlled crystal oscillator VCXO to the PXI 10 MHz reference clock signal PXI_CLK10 The VCXO output provides the source for the DDS chip which generates the sample clock timebase In this way the NI PXI 446x devices lock the sample clock timebase to PXI_CLK10 NI 446x Specifications Refer to the NI 446x Specifications for more detailed information about the NI 446x devices NI 447x Devices This section contains information about the NI 447x devices NI 447x Features The NI 447x devices are high performance high accuracy analog input devices for PXI and PCI The NI 447x devices have the following features e The NI 4472 features eight input channels e The NI 4472B features eight input channels with a lower cutoff frequency on AC coupled channels e The NI PCI 4474 features four input channels National Instruments Corporation A 13 NI Dynamic Signal Acquisition User Manual Append
96. to transition from 10 to 90 of the maximum signal amplitude A signal component with a positive slope that passes a threshold NI Dynamic Signal Acquisition User Manual G 10 ni com rms RTSI bus S sample rate self calibrating sensor SFDR Shannon Sampling Theorem signal conditioning single ended SMB SNR software trigger software triggering National Instruments Corporation G 11 Glossary Root mean square the square root of the average value of the square of the instantaneous signal amplitude a measure of signal amplitude Real time system integration bus the NI timing bus that connects devices directly for precise synchronization of functions Seconds Samples Sample rate is the rate at which data is sampled A property of a device that has an extremely stable onboard reference and calibrates its own A D and D A circuits without manual adjustments by the user A device that responds to a physical stimulus heat light sound pressure motion flow and so on and produces a corresponding electrical signal Spurious free dynamic range The dynamic range from full scale deflection to the highest spurious signal in the frequency domain See Nyquist Sampling Theorem The manipulation of signals to prepare them for digitizing A circuit that responds to the voltage on one input terminal and ground Sub miniature type B a type of coaxial connector Signal to noise ratio the ratio of
97. ts some form of data capture Transistor transistor logic Operating in a nominal range of 0 to 5 VDC with a signal below 0 8 V at logic low and a signal above 2 4 V at logic high Sampling at a rate lower than twice the Nyquist frequency can cause aliasing NI Dynamic Signal Acquisition User Manual G 12 ni com VCXO VDC VI Vin Vpk Vref W waveform Glossary Volts Voltage controlled crystal oscillator Volts direct current Virtual instrument a combination of hardware and or software elements typically used with a PC that has the functionality of a classic stand alone instrument a LabVIEW software module VI which consists of a front panel user interface and a block diagram program Volts in Voltage peak Reference voltage Multiple voltage readings taken at a specific sampling rate National Instruments Corporation G 13 NI Dynamic Signal Acquisition User Manual Index A AC coupling 2 3 ADC 2 8 AI EnhancedAliasRejectionEnable 2 10 alias rejection low frequency 2 10 analog 2 21 analog edge 2 21 analog edge with hysteresis 2 22 analog input 3 1 3 4 analog input features A 1 A 14 A 21 analog input filters 2 8 analog input programming 3 1 analog output 3 5 analog output NI PXI 4461 only 3 5 3 8 analog output features A 3 analog output filters 2 15 analog output programming NI PXI 4461 only 3 5 analog triggering 2 21 analog triggering modes
98. ts when it falls below 2 2 V as shown in Figure 2 9 Trigger ee E Figure 2 9 Analog Edge Triggering with Hysteresis on Rising Slope When using hysteresis with a falling slope the trigger is armed when the signal starts above Level plus the hysteresis value and asserts when the signal crosses below Level For example if you add a hysteresis of 1 V to a level of 3 2 V the signal must start at or rise above 4 2 V to arm the trigger The trigger asserts as the signal falls below 3 2 V and deasserts when it rises above 4 2 V as shown in Figure 2 10 4 2 V Hysteresis 3 2 V Level Trigger Eich Figure 2 10 Analog Edge Triggering with Hysteresis on Falling Slope Window Triggering A window trigger occurs when an analog signal either passes into enters or passes out of leaves a window defined by two levels Specify the levels by setting a value for the top and bottom window boundaries Figure 2 11 NI Dynamic Signal Acquisition User Manual 2 22 ni com Chapter 2 Dynamic Signal Acquisition Device Concepts demonstrates a trigger that acquires data when the signal enters the window You can also program the trigger circuit to acquire data when the signal leaves the window Window Top Window Bottom Trigger Figure 2 11 Window Triggering Triggering and Filter Delay Analog and digital triggering exhibit different behaviors with respect
99. tting Started Guide which you can download at ni com manuals The DAQ Getting Started Guide provides installation instructions and information on NI software tools and application development environments ADEs that you can use to configure and control DSA devices Installing Other Software If you are using other software such as another application development environment ADE refer to the installation instructions that accompany your software Installing the Hardware The DAQ Getting Started Guide contains general information on how to install PCI and PXI devices accessories and cables Device Pinouts Refer to the NI DAQmx Help for DSA device pinout information Select Start All Programs National Instruments NI DAQ NI DAQmx Help National Instruments Corporation 1 1 NI Dynamic Signal Acquisition User Manual Chapter 1 Getting Started Measurement System Overview A measurement system can consist of several components including a computer signal conditioning components and sensors Refer to the DAQ Getting Started Guide for a measurement system overview showing the path of physical phenomena to your measurement application Sensors and Transducers A sensor or transducer is a device that outputs an electrical signal in response to a measured physical phenomenon such as pressure or temperature The most common sensors for use with DSA devices include microphones for measuring sound pressure and acc
100. ual to 204 8 kS s the susceptible areas are centered around 32 64 96 and other multiples of 32 f NI 446x and NI 449x only because only the NI 446x and NI 449x devices support sample rates higher than 102 4 kS s e When you select a sample rate greater than 51 2 kS s and less than or equal to 102 4 kS s the susceptible areas are centered around 64 128 192 and other multiples of 64 f e When you select a sample rate greater than or equal to the minimum rate for the specific DSA device and less than or equal to 51 2 kS s the susceptible areas are centered around 128 256 384 and other multiples of 128 f ei Note On the NI USB 443x the susceptible areas are at multiples of 64 f regardless of the sample rate The susceptible frequency band is always one f wide For example if J 10 000 S s the digital filter can admit aliases from analog components between 1 275 MHz and 1 285 MHz In addition to the ADC built in digital filtering DSA devices feature a fixed frequency analog filter The analog filter removes high frequency components in the analog signal path before they reach the ADC This filtering addresses the possibility of high frequency aliasing from the narrow bands that are not covered by the digital filter Each input channel on a DSA device is equipped with a two pole lowpass Butterworth filter While the frequency response of the digital filter directly scales with the sample rate the analog filter 3 dB point
101. up Options directs you to pull down the File menu select the Page Setup item and select Options from the last dialog box National Instruments Corporation ix NI Dynamic Signal Acquisition User Manual About This Manual Ei A bold italic monospace NI USB 443x NI 446x NI 447x NI 449x Platform This icon denotes a note which alerts you to important information This icon denotes a caution which advises you of precautions to take to avoid injury data loss or a system crash When this symbol is marked on a product refer to the NI USB 443x Specifications NI 446x Specifications NI 447x Specifications or NI 449x Specifications for information about precautions to take Bold text denotes items that you must select or click in the software such as menu items and dialog box options Bold text also denotes parameter names Italic text denotes variables emphasis a cross reference or an introduction to a key concept Italic text also denotes text that is a placeholder for a word or value that you must supply Text in this font denotes text or characters that you should enter from the keyboard sections of code programming examples and syntax examples This font is also used for the proper names of disk drives paths directories programs subprograms subroutines device names functions operations variables filenames and extensions NI USB 443x refers to the NI USB 4431 and NI USB 4432 unless otherwise
102. us Figure A 22 NI 449x Block Diagram Connecting Signals to NI 449x Devices This section contains information about connecting signals to NI 449x devices NI 449x Fr ont Panels Figure A 23 shows the NI 4496 and NI 4498 front panels The NI 449x devices have Infiniband 4x connectors Refer to the NI DA Qmx Help for more information about the NI 449x connectors NI Dynamic Signal Acquisition User Manual A 22 ni com Appendix A Device Specific Information GA NATIONAL NATIONAL NATIONAL instruments INSTRUMENTS RS le NI PXI 4498 NI PXI 4498 NI PXle 4498 Ee PFIO PFIO Caution Connecting a signal that varies more than 5 V from the NI 449x ground reference to the ground shield of any input channel can result in damage to the device NI is not responsible for damage caused by such connections ZOU 4 0 LY O Cl e O HHH O 21 p Figure A 23 NI 449x Front Panels National Instruments Corporation A 23 NI Dynamic Signal Acquisition User Manual Appendix A Device Specific Information BNC Connector Polarity You can use an NI BNC 2144 or an Infiniband 4x to 8 BNC cable assembly to create BNC connectors from the NI 449x Figure A 24 shows the BNC connector polarity for all NI 4
103. y division on an internal signal Software that controls a specific hardware device such as a DAQ device or a GPIB interface device Dynamic signal acquisition Device under test The ratio of the largest signal level a circuit can handle to the smallest signal level it can handle usually taken to be the noise level normally expressed in decibels Electrostatic discharge The condition or state of an analog or digital signal A voltage pulse from an external source that triggers an event such as A D conversion A signal component with a negative slope that passes a threshold The frequency after the data passes through the DAC NI Dynamic Signal Acquisition User Manual Glossary Tes FIFO filter delay filtering Fin FIR floating signal sources fs G gain grounded source The effective sampling frequency First in first out memory buffer the first data stored is the first data sent to the acceptor FIFOs are often used on devices to temporarily store incoming or outgoing data until that data can be retrieved or output For example an AI FIFO stores the results of A D conversions until the data can be retrieved into system memory a process that requires the servicing of interrupts and often the programming of the DMA controller This process can take several milliseconds in some cases During this time data accumulates in the FIFO for future retrieval With a larger FIFO longer latencies can be tole

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