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NI PXIe-4339 User Manual

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1. 0 0 00 R Mod le Pout Gaia a air V O Connector Signal Description ooccicncnnnnnnncnnnnnnacononnnnonnnncononono cacao nncnnon caca ranas NEPX1e24339 Block Didpram simnotasioo tiles rec espada Wide Bandwidth Analog Output oooconconcnicnicnnonionnoncononncnn cono noonconnon non con ron ronncnnnonnnnnns Signal Acquisition Considerations Software Scaling and Equations Nyquist Frequency and Nyquist Bandwidth Analog Input Filters cece eesesseecnsesceecseseceecsesensecessesacnessceaesesecsesaceesaeeecsesessesaees Anti Alias Filters colita crecer Passbanid 1 ias Stopband eee Alias Free Bandwidth Filter Group Delay Supported Data Rates oooncicncnnnncicnococnnnonncncononanonacinon Hardware Timed Single Point Acquisitions Hardware Timed Single Point Acquisition Model o ononnccnnnnncnnnnnnccnncnnnocnnncnnononos Maximum HWTSP Rate AnalySis ccescessesessesceeeceeceeceeceseesesaeaeaecsecaecaeeaeeaeeneens 2 kHz Control Loop Rate Calculation Example oooconicnciccnoninncnnonaccnnacinonacnnn 2 29 O National Instruments v Contents Timing and Triggering ceececececcesseseeseesecsecaecsseseeeseeseceecseescescesceseeseceececeeeaeease 2 30 Sample Clock Timebase ooooooconnccicnnonicnnonoonoonoanonncnnonnonn cono nonnconnonnon non i nono 2 30 External Clock tt EE ero bn A 2 31 Digital Trigger ita e ride 2 31 Analog TIO ii id a
2. physical reading mx V When the calibration certificate of the sensor provides a table of more than two calibration points or a polynomial expression table or polynomial scaling can produce more accurate results by compensating for non linearity in the response of the sensor Table scaling requires providing NI DAQmx with a set of electrical values and corresponding physical values Polynomial scaling requires providing NI DAQmx with the forward and reverse coefficients ofa polynomial representing the response of the sensor If you only know one set of coefficients you can use the DAQmx Compute Reverse Polynomial Coefficients VI function to determine the other set Refer to the NMI DAQmx Help for more information about the DAQmx Compute Reverse Polynomial Coefficients VI function Shielding and Grounding Considerations A Caution To ensure the specified EMC performance operate this product only with shielded cables and accessories Cables connected to the NI PXIe 4339 using the TB 4339 B C terminal block must use only twisted shielded pair cables Use one twisted shielded pair for each EX EX RS RS AI AI PFIO DGND AO AOGND and T DGND that is cabled Cable shields must be terminated to chassis ground at both ends Module Pinout This is the pinout represented on the front connector of the NI PXIe 4339 Refer to the I O Connector Signal Description section for definitions of each signal Refer to the terminal block installatio
3. 7 pu KA Analog Comparison Reference Trigger 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 26 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 Figure 2 26 Window Triggering Window Top Window Bottom Analog Comparison Reference Trigger Triggering and Filter Delay The NI PXIe 4339 can use a digital trigger signal from the backplane or the PFI from the front connector as either a start trigger initiating an acquisition or a reference trigger in the middle of an acquisition The NI PXIe 4339 can also generate an analog trigger event from its digitized ADC data As a result of the way the NI PXIe 4339 modules adjust for its digital filter group delay analog triggers can only act as reference triggers In all cases the NI PXIe 4339 interprets triggers based on where they occur in time The hardware automatically compensates for its group delay such that data from this module will line up closely in time with the occurrence of the trigger event However the group delay affects how O National Instruments 2 33 Chapter 2 Using the Modul
4. g vwe WWW i 1 i 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 i 1 1 1 1 1 1 1 i 1 1 1 1 F The following symbols apply to the circuit diagram and equations R andR gt Half bridge completion resistors located inside the NI PXIe 4339 e R3 Quarter bridge completion resistor located inside the TB 4339 B C R must be equal to the nominal resistance of the active gage Ry e Rsc Shunt calibration resistor located inside the TB 4339 B C R Active element measuring tensile strain You provide this element R Lead resistance The resistance in the EX and QTR field wiring should match e GF Gage Factor specified by the gage manufacturer Vey Measured voltage of the bridge V x Excitation voltage provided by the NI PXIe 4339 Rpyotect 10 kQ resistor in series with the Shunt Cal A switch to protect against external fault voltages The total shunt cal resistance is equal to the Rgc and Rp otect series combination e V Offset compensated ratiometric bridge output defined by the following equation 7 pa P Ve X YA Note The ratio of the bridge output voltage and the excitation voltage is done internally on the NI PXIe 4339 O National Instruments 2 5 Chapter 2 Using the Module To convert module readings to strain use the following equation 4V strain GFO 27 r To compensate for lead resistance errors use shunt c
5. Rprotect The following symbols apply to the circuit diagram and equations R and R Half bridge completion resistors located inside the NI PXIe 4339 R Quarter bridge completion resistor located in close proximity to the active gage R must be equal to the nominal resistance of the active gage Ry Rsc Shunt calibration resistor located inside the TB 4339 B C R Active element measuring tensile strain 8 R Lead resistance GF Gage Factor specified by the gage manufacturer Vcy Measured voltage of the bridge Vexy Excitation voltage provided by the NI PXIe 4339 Rpyotect 10 KQ resistor in series with the Shunt Cal A switch to protect against external fault voltages The total shunt cal resistance is equal to the Rsc and Rpyotect series combination V Offset compensated ratiometric bridge output defined by the following equation 7 et A A Vg X Note The ratio of the bridge output voltage and the excitation voltage is done internally on the NI PXIe 4339 O National Instruments 2 7 Chapter 2 Using the Module To convert module readings to strain use the following equation 3 _ 47 strain GF 2V Half Bridge Type This section provides information for the half bridge strain gage configuration type I The half bridge type I measures either axial or bending strain Figure 2 7 shows how to position strain gage resistors in an axial and bending configurations F
6. Any application taking more than 480 us will fail to close the 2 kHz control loop When analyzing the bandwidth of the system you must consider the group delay of all the components of the system When using only the NI PXIe 4339 internal 2 kHz filter the bandwidth of the control loop is as follows 1 trol Bandwidth gt coniro Banawi Transfer Time Application Time Filter Group Delay 1 Control Bandwidth 20 us 480 us 120 us Control Bandwidth 1 613 kHz Note You can increase the bandwidth of the system by either reducing the application time or by using another filter option with lower group delay Timing and Triggering This section contains information about timing and triggering theory of operation Sample Clock Timebase The ADCs require an oversample clock to drive the conversion The oversample clock frequency is greater than the sample rate On the NI PXIe 4339 modules the oversample clock is produced from a 100 MHz reference clock This 100 MHz reference clock can be supplied 2 30 ni com NI PXle 4339 User Manual either by an onboard oscillator or by the PXIe backplane 100 MHz clock Multiple modules can be synchronized by selecting the PXIe backplane 100 MHz clock as the reference clock source for all the modules Refer to the Reference Clock Synchronization section for more information External Clock The NI PXIe 4339 ADCs cannot be clocked from external sources such as encoders or tachometers
7. 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 Digital Triggering You can configure the NI PXIe 4339 modules to start an acquisition in response to a digital trigger signal from one of the PXI Express backplane trigger lines or the PFI from the front connector The trigger circuit can respond either to a rising or a falling edge Analog Triggering Analog triggering allows you to trigger your application based on an input signal and trigger level you define You can configure the analog trigger circuitry to monitor any input channel acquiring data Choosing an input channel as the trigger channel does not change the input channel acquisition specifications The analog trigger signal can be used as a reference trigger only In a reference triggered acquisition you configure the module to acquire a certain number of pre trigger samples and a certain number of post trigger samples Reference triggered acquisitions can therefore only be configured as Finite tasks The analog trigger on the NI PXIe 4339 cannot be used as a start trigger This restriction is a result of the way the module compensates for the filter group delay When using an analog reference trigger the module first waits for the specified number of
8. that is of interest To accurately measure the ratiometric output of a bridge based sensor both the bridge output voltage V and the excitation voltage Vy must be known Determination of the excitation voltage can be accomplished by either using an accurate voltage source or by measuring it The NI PXIe 4339 uses circuitry that continuously measures the excitation voltage and applies it as a reference to its analog to digital converter ADC In this way the NI PXIe 4339 compensates for variations in the excitation voltage and the module returns data as a ratio of the bridge output voltage to the excitation voltage Connection Options to Correct for Resistance Errors The basic Wheatstone bridge in Figure 2 1 shows the excitation voltage impressed directly across the bridge However field wiring used to connect sensors to measurement devices have a non zero resistance and this resistance can create errors in bridge circuit measurements The NI PXIe 4339 provides two mechanisms to correct for these errors remote sensing and shunt calibration Remote Sensing Remote sensing continuously and automatically corrects for errors in excitation leads and generally is most appropriate for half and full bridge sensors Moreover its use is most critical in applications that employ long wires and or small gauge wires as these have higher resistance The resistance in the wires that connect the excitation voltage to the bridge causes a voltage drop
9. Description AIGND Analog Input Ground AOGND Analog Output Ground AI lt O 7 gt Input Analog Input Channels 0 to 7 AJF and Al are the AI lt O 7 gt positive and negative inputs of the differential analog input SCA lt 0 7 gt These pins provide the connection point to the shunt calibration switch EX lt 0 7 gt Output Provides the differential bridge excitation voltage EX lt 0 7 gt RS lt 0 7 gt Input Remote sense input The remote sense pins sense RS lt 0 7 gt the actual voltage applied to the bridge AO lt 0 7 gt Output Wide Bandwidth Analog Output Channels 0 to 7 ground referenced to AOGND This signal is a current limited and external voltage fault protected copy of the first gain stage output T lt 0 7 gt Input Output TEDS sensor digital communication lines referenced to DGND RSVD These pins are reserved for communication with the accessory DGND Digital ground these pins supply the reference for module digital signals and are connected to the module digital ground PFI Input Output 3 3 V digital signal for sending or receiving trigger and synchronization signals This line is referenced to DGND 2 22 ni com NI PXle 4339 User Manual NI PXle 4339 Block Diagram Figure 2 18 shows the analog input circuitry block diagram of the NI PXIe 4339 The NI PXIe 4339 has two measurement modes Voltage mode is used to measure voltag
10. E ENE 2 31 Triggering and Filter Delays penean asa ae 2 33 Synchro ZAN esini O E A 2 34 Reference Clock Synchronization ccececcessesseseceeceseeseseesecsecseeseeneeaeeneeseees 2 34 TEDS rera o A Ii E ee 2 35 Configuring and Using TEDS in Software ooooccicnonnoccnononnnononncnncononncnnncnnonnonnnns 2 36 Accessory Auto Detection ccccceccssessessecseescesceseeseeseeseeseeecesceeceeceaeeaecaecaeeaeenaenaente 2 36 Chapter 3 SC Express Considerations SC Express Clock and Trigger Signals ccccssessesseescescescesceseeeeeeeceeceaeeeeaeeaeenecaeensenee 3 1 PXTe _ CLK 100 kon honeta ansa a aa i a aA aaan aaa Aa 3 1 PRE SY NN 3 1 PIE CERO ayes O anstindtotenstes T O 3 1 PXI Ti GS OTS cirio an eE EEEE iii aii 3 1 IAN cccccecceeseescescescesceseeseeseesecaecaecsecaceseeesecsecseeseeseesceseeeeeeeteeseeeeeaees 3 2 PXTe DSTARSA Cota liado ados 3 2 Appendix A Offset Nulling Bridge Balancing Appendix B NI Services Figures Figure 2 1 Basic Wheatstone Bridge Circuit Diagram ooooncnncnicincnncnnncnncnncnnncnncnnon Figure 2 2 Connecting Remote Sense Wires to the NI PXIe 4339 Figure 2 3 Quarter Bridge Type I Measuring Axial and Bending Strain 2 4 Figure 2 4 Quarter Bridge I Circuit Diagram ee eeeeeseseeeceeeeeeseeeeceeeeeeseeeees 2 5 Figure 2 5 Quarter Bridge Type II Measuring Axial and Bending Strain 2 6 Figure 2 6 Quarter Bridge IT Circuit Diagram ee eeseseeseeeeee
11. IN THE OPERATION OF NUCLEAR FACILITIES AIRCRAFT NAVIGATION AIR TRAFFIC CONTROL SYSTEMS LIFE SAVING OR LIFE SUSTAINING SYSTEMS OR SUCH OTHER MEDICAL DEVICES OR ANY OTHER APPLICATION IN WHICH THE FAILURE OF THE PRODUCT OR SERVICE COULD LEAD TO DEATH PERSONAL INJURY SEVERE PROPERTY DAMAGE OR ENVIRONMENTAL HARM COLLECTIVELY HIGH RISK USES FURTHER PRUDENT STEPS MUST BE TAKEN TO PROTECT AGAINST FAILURES INCLUDING PROVIDING BACK UP AND SHUT DOWN MECHANISMS NI EXPRESSLY DISCLAIMS ANY EXPRESS OR IMPLIED WARRANTY OF FITNESS OF THE PRODUCTS OR SERVICES FOR HIGH RISK USES Contents Chapter 1 Getting Started Install A Aa A ari 1 Module Specifications Module Accessories iras 1 Chapter 2 Using the Module Connecting Signal snadin iaa n iiedivnsiiomsbondes A a O es 2 1 Wheatstone Bridgesin i on i 2 1 Connection Options to Correct for Resistance Errors oocoocincnonicnnoconinconcnnoncnnoncnann 2 2 REMOS C118 1105 vsce Sec A vp AS Shunt Calibration sss oaa es Sa Bihar oi he a eS Strain Gage Sensor Configurations Quarter Bridge Type I 00 Quarter Bridge Type II gt Half Bridge Type iii eta Half Bridge Ty pe llo io da F llEBridas IPs an a ted Full Bridge Type Ticoconi nioninond non cvacsctbvccsssscevcusce sevecsscd svsseacredecdecdsadecueesacvess Full Bridge Type IM oo cece eeeeeeeeseneeecteeneees Force Pressure and Torque Sensor Configurations Shielding and Grounding Considerations
12. R Protect The following symbols apply to the circuit diagram and equations R Active element measuring compressive strain s R Active element measuring tensile strain 8 R Active element measuring compressive strain s R Active element measuring tensile strain 8 Rsc Shunt calibration resistor located inside the TB 4339 B C R Lead resistance GF Gage Factor specified by the gage manufacturer Ve Measured voltage of the bridge Vix Excitation voltage provided by the NI PXIe 4339 Rprotec 10 KO resistor in series with the Shunt Cal A switch to protect against external fault voltages The total shunt cal resistance is equal to the Rgc and Rpyotect Series combination V Offset compensated ratiometric bridge output defined by the following equation 7 ea data e gt E gt _ __ Note The ratio of the bridge output voltage and the excitation voltage is done internally on the NI PXIe 4339 Vg X O National Instruments 2 13 Chapter 2 Using the Module To convert module readings to strain use the following equation strain e Full Bridge Type Il This section provides information for the full bridge type II strain gage configuration The full bridge type II only measures bending strain Figure 2 13 shows how to position strain gage resistors in a bending configuration Figure 2 14 shows the full bridge type II circuit wiring diagram Figure 2 13 Full Bridge
13. as the negative ratio of transverse strain to axial strain longitudinal strain Poisson s ratio is a material property of the specimen you are measuring Vey Measured voltage of the bridge Vix Excitation voltage provided by the NI PXIe 4339 Rpyotect 10 KO resistor in series with the Shunt Cal A switch to protect against external fault voltages The total shunt cal resistance is equal to the Rgc and Rpyotect series combination V Offset compensated ratiometric bridge output defined by the following equation 7 E strained V cp pa r A A Ve X al Note The ratio of the bridge output voltage and the excitation voltage is done internally on the NI PXTe 4339 O National Instruments 2 9 Chapter 2 Using the Module To convert module readings to strain use the following equation A V strain GF 1 v 2V v 1 Half Bridge Type II This section provides information for the half bridge strain gage configuration type II The half bridge type II only measures bending strain Figure 2 9 shows how to position strain gage resistors in a bending configuration Figure 2 10 shows the half bridge type II circuit wiring diagram Figure 2 9 Half Bridge Type II Rejecting Axial and Measuring Bending Strain Rejects Axial Measures Bending A half bridge type II configuration has the following characteristics e Two active strain gage elements One strain gage element is mounted in the direction of bending
14. differential star DSTAR lines and how they are used Table 3 1 PXle_DSTAR Line Descriptions Trigger Line Purpose PXIe DSTARA Distributes high speed high quality clock signals from the system timing slot to the peripherals input PXIe DSTARB Distributes high speed high quality trigger signals from the system timing slot to the peripherals input PXIe_ DSTARC Sends high speed high quality trigger or clock signals from the peripherals to the system timing slot output The DSTAR lines are only available for PXI Express devices when used with a PXI Express system timing module For more information refer to the PXI Express Specification at www pxisa org 3 2 ni com Offset Nulling Bridge Balancing When you install a bridge based sensor the bridge probably will not output exactly 0 V when not under load Slight variations in resistance among the bridge legs generate some nonzero initial offset voltage Use the DAQmx Perform Bridge Offset Nulling Calibration VI function or the DAQ Assistant to perform an offset nulling calibration which will apply software compensation for the bridge NI DAQmx will measure the bridge while not under load and then use this measurement as the initial bridge voltage when scaling readings from the bridge This method is simple fast and requires no manual adjustments The disadvantage of the software compensation method in contrast to hardware compensation is t
15. frequency aliasing from the narrow bands that are not covered by the digital filter While the frequency response of the digital filter directly scales with the sample rate the analog filter 3 dB point is fixed The NI PXIe 4339 automatically adjusts its oversample rate to maintain a high level of alias protection regardless of the current sampling rate Passband The signals within the passband have frequency dependent gain or attenuation The small amount of variation in gain with respect to frequency is called the passband flatness The digital filters of the NI PXIe 4339 adjust the frequency range of the passband to match the sample rate Therefore the amount of gain or attenuation at a given frequency depends on the sample rate Stopband The filter significantly attenuates all signals above the stopband frequency The primary goal of the filter is to prevent aliasing Therefore the stopband frequency scales precisely with the sample rate The stopband rejection is the minimum amount of attenuation applied by the filter to all signals with frequencies within the stopband Alias Free Bandwidth Any signal that appears in the alias free bandwidth of the NI PXIe 4339 is not an aliased artifact of signals at a higher frequency The alias free bandwidth is defined by the ability of the filter to reject frequencies above the stopband frequency and it is equal to the sample rate minus the stopband frequency Looser filters with degrad
16. 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 or contact your local office at ni com contact You also can visit the Worldwide Offices section of ni com niglobal to access the branch office websites which provide up to date contact information support phone numbers email addresses and current events B 2 ni com
17. physical and electrical physical These should be based on the calibration certificate of the sensor if one is available otherwise they can be based on the specifications or data sheet of the sensor Any two points can be used assuming that they are far enough apart to accurately determine the slope of the linear scaling equation For example e physical The zero point of the sensor zero force pressure or torque electrical The electrical output corresponding to the zero point of the sensor in mV V or V V e physical The maximum physical reading of the sensor or capacity maximum load pressure or torque electrical The electrical output corresponding to the maximum physical reading of the sensor in mV V or V V Note Some sensor calibration certificates specify the electrical output in mV or V not mV V or V V If this is the case divide the specified electrical output by the excitation voltage at which the calibration was performed The two point linear conversion uses the following equations physical physical m _ _ _ ___ electrical electrical b physical m x electrical Physical reading mxV b National Instruments 2 19 Chapter 2 Using the Module If offset nulling bridge balancing is used to compensate for offset then the zero point of the sensor can be assumed to output exactly 0 V V simplifying these equations physical m electrical
18. trigger lines may be divided into multiple independent buses Refer to the documentation for your chassis for details PXI_STAR Trigger In a PXI Express system the Star Trigger bus implements a dedicated trigger line between the system timing slot and the other peripheral slots The Star Trigger can be used to synchronize multiple modules or to share a common trigger signal among modules A system timing controller can be installed in the system timing slot to provide trigger signals to other peripheral modules Systems that do not require this functionality can install any standard peripheral module in this system timing slot An SC Express module receives the Star Trigger signal PXI_STAR from a System timing controller PXI_STAR can be used as a trigger signal for input operations An SC Express module is not a System timing controller An SC Express module can be used in the system timing slot of a PXI system but the system will not be able to use the Star Trigger feature PXle_DSTAR lt A C gt PXI Express devices can provide high quality and high frequency point to point connections between each slot and a system timing slot These connections come in the form of three low voltage differential star triggers that route between a PXI Express system timing controller and a peripheral device Using multiple connections simplifies the creation of applications because of the increased routing capabilities Table 3 1 describes the three
19. 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 National Instruments 2 25 Chapter 2 Using the Module 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 The NI PXIe 4339 modules employ both digital and analog lowpass filters to achieve this protection The NI PXIe 4339 modules 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 located at frequencies far above the sampling rate These frequencies are referred to as the ADC alias holes In addition to the digital filtering the NI PXIe 4339 modules 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
20. which is a source of gain error The NI PXIe 4339 includes remote sensing to compensate for this gain error Connect remote sense inputs of the NI PXIe 4339 to the excitation voltage wires of the sensor as close to the bridge circuit as possible Refer to the full bridge diagram in Figure 2 2 for an illustration of how to connect remote sense wires Figure 2 2 Connecting Remote Sense Wires to the NI PXle 4339 NI PXle 4339 RS EX Al Al i EX RS 2 2 ni com NI PXle 4339 User Manual The actual bridge excitation voltage measured at the bridge is smaller than the voltage sourced at the EX and EX connector pins This reduction in voltage is due to the voltage drop across the excitation lead wire resistance Rj qq If you do not use remote sensing of the actual bridge voltage the resulting reduction in gain is given by the following equations R e for half bridge sensors reaa g 2xR e for full bridge sensors AR Ro If you connect the remote sense signals directly to the bridge resistors the NI PXIe 4339 senses the actual bridge voltage using high impedance RS leads and eliminates the gain errors caused by the resistance of the EX and EX leads Shunt Calibration Shunt calibration can correct for errors from the resistance of both the excitation wiring and wiring in the individual resistors of the bridge While remote sensing only corrects for resistances from the EX leads on the NI PXIe 4339 to the senso
21. 0 50 T 0 2 T 20 x 80 20 0 5 50 200 1 10 1 000 4 000 Signal Acquisition Considerations This section contains information about signal acquisition concepts including software scaling and equations Delta Sigma converters Nyquist frequency and bandwidth timing triggering and synchronization Software Scaling and Equations After you have acquired the signal of interest you can scale this measurement to the appropriate units in software This is done automatically for you in NI DAQmx if using certain tasks such as strain or channel types You also can scale the measurements manually in your application using the measurement to strain conversion equations provided in this document for each 2 24 ni com NI PXle 4339 User Manual configuration type The NI PXIe 4339 also supports measurements for force pressure torque bridge V V and custom voltage with excitation Finally there are voltage to strain conversion functions included in LabVIEW and NI DAQmx In LabVIEW the conversion function Convert Strain Gage Reading VI is in the Data Acquisition Signal Conditioning subpalette The prototypes for the NI DAQ functions Strain_Convert and Strain_Buf_Convert are in the header file convert h for C C and convert bas for Visual Basic Refer to the Measurements Fundamentals book of the LabVIEW Help for more information The strain gage types in these sections directly correspond to bridge se
22. Finder Consider the following caveat to using Reference Clock synchronization The NI PXIe 4339 automatically compensates for its filter group delay However some other device families do not compensate for their filter delay In this case manually compensate for group delay in the waveforms when you synchronize between device families 1f this level of synchronization is required for your application TEDS The NI PXIe 4339 supports communicating with Transducer Electronic Data Sheet TEDS enabled sensors IEEE 1451 4 Class 2 TEDS enabled sensors carry a built in self identification EEPROM containing a table of parameters and sensor information This allows your data acquisition system to automatically detect and configure the 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 For more information about TEDS plug and play sensors refer to ni com pnp National Instruments 2 35 Chapter 2 Using the Module Configuring and Using TEDS in Software To manually configure TEDS in MAX right click on the NI PXIe 4339 module within the Configuration tree Then select Configure TEDS from the pop up menu To programmatically configure TEDS call the DAQmx Configure TEDS VI Accessory Auto Detection SC Expres
23. Refer to the NI PXTe 4339 Specifications for more information O National Instruments 2 27 Chapter 2 Using the Module When transferring data to the PXIe controller or computer HWTSP operations are used to read single samples at known time intervals While buffered operations are optimized for high throughput HWTSP operations are optimized for low latency These features make HWTSP ideal for real time control applications HWTSP operations in conjunction with the wait for next sample clock function provide more deterministic synchronization between the software layer and the hardware layer Refer to the N DAQmx Hardware Timed Single Point Lateness Checking document for more information To access this document go to ni com info and enter the Info Code daghwtsp Hardware Timed Single Point Acquisition Model The HWTSP data path is optimized for low latency applications and is different than that which is used in buffered acquisition model default When in HWTSP mode the filtering and sampling systems can be modeled as being decoupled which allows you to configure the filter and sampling rate independently Figure 2 19 shows the HWTSP data path model Figure 2 19 HWTSP Data Path Model Analog Front End gt el gn A A D gt PXle Controller or Computer The ADC samples the input stream and returns it to the PXIe controller or computer at every SampleClock signal Maximum HWTSP Rate Analysis When in HWTSP the
24. Reference Trigger i Analog Edge Triggering With Hysteresis When you add hysteresis to analog edge triggering you add a window above or below the trigger level This triggering mode often is used to reduce false triggering due to noise or jitter in the signal For example if you add a hysteresis of 1 mV V to the example in Figure 2 23 which uses a level of 3 2 mV V the signal must start at or drop below 2 2 mV V to arm the trigger The analog comparison becomes true when the signal rises above 3 2 mV V and becomes false when it falls below 2 2 mV V as shown in Figure 2 24 Figure 2 24 Analog Edge Triggering with Hysteresis on Rising Slope 3 2 mV V Level _ AO CA A EEIEIEE ae INS a Hysteresis 2 2 mV V si AN LEIEN EEEIEE EEE Analog Comparison Reference Trigger 2 32 ni com NI PXle 4339 User Manual 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 mV V to a level of 3 2 mV V the signal must start at or rise above 4 2 mV V to arm the trigger The analog comparison becomes true as the signal falls below 3 2 mV V and becomes false when it rises above 4 2 mV V as shown in Figure 2 25 Figure 2 25 Analog Edge Triggering with Hysteresis on Falling Slope 4 2 MVV ra rr fo see Hysteresis 3 2 mV V Level b
25. SC Express NI PXle 4339 User Manual 8 Ch 24 bit 25 6 kS s Universal Bridge Input Module April 2015 7 NATIONAL 376020B 01 DI INSTRUMENTS Worldwide Technical Support and Product Information ni com Worldwide Offices Visit ni com niglobal to access the branch office websites which provide up to date contact information support phone numbers email addresses and current events National Instruments Corporate Headquarters 11500 North Mopac Expressway Austin Texas 78759 3504 USA Tel 866 ASK MYNI 275 6964 For further support information refer to the M Services appendix To comment on National Instruments documentation refer to the National Instruments website at ni com info and enter the Info Code feedback O 20142015 National Instruments All rights reserved Legal Information Limited Warranty This document is provided as is and is subject to being changed without notice in future editions For the latest version refer to ni com manual s NI reviews this document carefully for technical accuracy however NI MAKES NO EXPRESS OR IMPLIED WARRANTIES AS TO THE ACCURACY OF THE INFORMATION CONTAINED HEREIN AND SHALL NOT BE LIABLE FOR ANY ERRORS NI warrants that its hardware products will be free of defects in materials and workmanship that cause the product to fail to substantially conform to the applicable NI published specifications for one 1 year from the date of invoice For a period of ninety 90 days f
26. Type II Rejecting Axial and Measuring Bending Strain Ro ve Rejects Axial Measures Bending A full bridge type II configuration has the following characteristics Four active strain gage elements Two are mounted in the direction of bending strain with one on one side of the strain specimen top and the other on the opposite side bottom The other two act together as a Poisson gage and are mounted transverse perpendicular to the principal axis of strain with one on one side of the strain specimen top and the other on the opposite side bottom e Rejects axial strain e Sensitivity 1 3 uV V per ps for GF 2 0 2 14 ni com NI PXle 4339 User Manual Figure 2 14 Full Bridge Type ll Circuit Diagram NI PXle 4339 Set Bridge Transducer TB 4339 B C Configuration to Full Bridge Al i g i Von D EX gt a i Al OS EX gt SCA a Shunt i Cal A SGA WW ew Rsc Ferotect i The following symbols apply to the circuit diagram and equations R Active element measuring compressive Poisson effect ve R Active element measuring tensile Poisson effect ve R Active element measuring compressive strain s R Active element measuring tensile strain 8 Rsc Shunt calibration resistor located inside the TB 4339 B C R Lead resistance GF Gag
27. VWV SW i Rprotect The following symbols apply to the circuit diagram and equations R through R Active elements of the bridge located inside the sensor e Rsc Shunt calibration resistor located inside the TB 4339 B C e R Lead resistance Vou Measured voltage sensor output Sensors that measure force pressure or torque through other means for example piezoelectric force sensors cannot be used with the NI PXIe 4339 2 Sensors that contain a built in voltage or current amplifier can be used with the NI PXIe 4339 in voltage mode 2 18 ni com NI PXle 4339 User Manual Vex Excitation voltage provided by the NI PXIe 4339 Rprotec 10 KO resistor in series with the Shunt Cal A switch to protect against external fault voltages The total shunt cal resistance is equal to the Rgc and Rproteo series combination V Offset compensated ratiometric bridge output defined by the following equation Vey under load V cy no load Mr Vix Note The ratio of the bridge output voltage and the excitation voltage is calculated internally on the NI PXIe 4339 Converting module readings to physical force pressure or torque readings can be performed using linear table or polynomial scaling In NI DAQmx linear scaling for bridge based force pressure and torque sensors is done based on two points which are specified as pairs of corresponding physical and electrical values electrical
28. Vg X Note The ratio of the bridge output voltage and the excitation voltage is done internally on the NI PXTe 4339 O National Instruments 2 11 Chapter 2 Using the Module To convert module readings to strain use the following equation 2V strain an Full Bridge Type This section provides information for the full bridge strain gage configuration type I The full bridge type I only measures bending strain Figure 2 11 shows how to position strain gage resistors in a bending configuration Figure 2 12 shows the full bridge type I circuit wiring diagram Figure 2 11 Full Bridge Type Rejecting Axial and Measuring Bending Strain Ro 8 Rejects Axial Measures Bending A full bridge type I configuration has the following characteristics e Four active strain gage elements Two strain gage elements are mounted in the direction of bending strain on one side of the strain specimen top while the other two are mounted in the direction of bending strain on the opposite side bottom Highly sensitive to bending strain e Rejects axial strain e Sensitivity 2 V V per pe for GF 2 0 2 12 ni com NI PXle 4339 User Manual Figure 2 12 Full Bridge Type Circuit Diagram Transducer TB 4339 B C NI PXle 4339 Set Bridge Configuration to Full Bridge Shunt Cal A WWW
29. a from the next Sample Clock being returned as the first point in the acquisition Refer to the Triggering and Filter Delay section for more details about how this affects analog trigger events On demand software sampling returns a single sample from an acquisition running at the maximum supported sample rate of the module For any on demand software timed acquisition the NI PXIe 4339 waits for the group delay to elapse before returning the sample As a result the data returned aligns closely in time with when the data was requested and is delayed by the sum of the analog input delay and digital filter delay The maximum sample rate of the NI PXIe 4339 is 25 6 kS s Supported Data Rates The NI PXIe 4339 supports rates of 1 S s to 25 6 kS s Hardware Timed Single Point Acquisitions Hardware Timed Single Point HWTSP is a hardware timed acquisitions mode in which a digital hardware signal SampleClock controls the rate of the acquisition and data that is transferred to a PXIe controller or computer through HWTSP operations The SampleClock signal is internally generated in the NI PXIe 4339 using the sample rate configured in the NI DAQmx task The maximum sample rate of the NI PXIe 4339 is 25 6 kS s In addition to the fixed analog input delay you must also account for the digital filter group delay For 25 6 kS s the digital filter group delay is 48 5 S Ifa 10 V range is used total delay is 3 8043 ms 6 1 us 3 8104 ms
30. alibration Quarter Bridge Type II This section provides information for the quarter bridge strain gage configuration type II The quarter bridge type II configuration measures either axial or bending strain Figure 2 5 shows how to position a strain gage resistor in an axial and bending configurations Figure 2 6 shows the quarter bridge type II circuit wiring diagram Figure 2 5 Quarter Bridge Type ll Measuring Axial and Bending Strain A quarter bridge type II has the following characteristics One active strain gage element and one passive quarter bridge element dummy gage used for temperature compensation The active element R4 is mounted in the direction of axial or bending strain The dummy gage R3 is mounted in close thermal contact with the strain specimen but not bonded to the specimen and is usually mounted perpendicular to the principal axis of strain e Completion resistors R and R provide half bridge completion These resistors are provided by the NI PXIe 4339 module e Sensitivity 0 5 1 V V per us for GF 2 0 2 6 ni com NI PXle 4339 User Manual Figure 2 6 Quarter Bridge II Circuit Diagram NI PXle 4339 Set Bridge Configuration to Transducer TB 4339 B C Quarter Bridge II or Half Bridge Al EX i Ry i R i EX 1 2 SCA rot i O Shunt i SCA i af CalA O WW Rsc
31. arter bridge type I measures either axial or bending strain Figure 2 3 shows how to position a strain gage resistor in an axial and bending configuration Figure 2 4 shows the quarter bridge type I circuit wiring diagram Figure 2 3 Quarter Bridge Type Measuring Axial and Bending Strain Bending A quarter bridge type I configuration has the following characteristics Asingle active strain gage element is mounted in the principal direction of axial or bending strain A passive quarter bridge completion resistor R3 is required in addition to half bridge completion resistors R and R3 e Halfbridge completion resistors R and R3 are provided by the NI PXIe 4339 module The quarter bridge completion resistor R3 is provided on the TB 4339 B C terminal blocks The shunt calibration resistor Rsc is provided on the TB 4339 B C terminal blocks The shunt cal A switch is provided on the NI PXIe 4339 module e Sensitivity 0 5 uV V per pe for GF 2 0 2 4 ni com NI PXle 4339 User Manual Figure 2 4 Quarter Bridge Circuit Diagram NI PXle 4339 Set Bridge Configuration Transducer TB 4339 B C to Quarter Bridge R i L Al a Ab i EX fe R4 3 i i i gage i i o i i i AL R3 i ma ETEA ja EX i a SCA A i i f Shunt i SCA Rsc 7 Ferotect g Cal A i
32. cation at www pxisa org PXle_SYNC100 PXIe SYNC100 is a common low skew 10 MHz reference clock with a 10 duty cycle for synchronization of multiple modules in a PXI Express measurement or control system The PXI Express backplane is responsible for generating PXle_SYNC100 independently to each peripheral slot in a PXI Express chassis PXIle SYNC100 allows modules using PXle_CLK100 as their reference to recreate the timing of the PXI_CLK10 signal while taking advantage of the lower skew of PXIe_CLK100 For more information refer to the PXI Express Specification at www pxisa org PXI_CLK10 PXI_CLK10 is a common low skew 10 MHz reference clock for synchronization of multiple modules in a PXI measurement or control system The PXI backplane is responsible for generating PXI_CLK10 independently to each peripheral slot in a PXI chassis In PXIe chassis the PXI_CLK10 signal is in phase with PXIe_CLK100 al Note PXI_CLK10 cannot be used as a reference clock for SC Express modules PXI Triggers A PXI PXTe chassis provides eight bused trigger lines to each module in a system Triggers may be passed from one module to another allowing precisely timed responses to asynchronous external events that are being monitored or controlled Triggers can be used to synchronize the operation of several different PXI peripheral modules O National Instruments 3 1 Chapter 3 SC Express Considerations In a PXI chassis with more than eight slots the PXI
33. cess Figure 2 21 Typical Control System Control Loop Time 500 us Al Measurement PXle Controller or Computer 4 gt DAQ Device gt Process AO Stimulus To successfully close a 2 kHz control loop make sure that the time between the time the AI sample is acquired and the time the AO stimulus is generated is lt 500 us Refer to Figure 2 22 Figure 2 22 Input and Output of a Control System with Bandwidth gt 2 kHz Time gt Sample 0 Sample 1 2 kHz Input 2 kHz Output Sample 0 Sample 1 Transfer Application lt 500 us O National Instruments 2 29 Chapter 2 Using the Module To make sure that your application can run and control a process at 2 kHz and that the first output is generated within the first sample period make sure that the following conditions are satisfied 500 us lt Transfer Time Application Time 2 1 Where Transfer Time the time it takes to transfer samples between the DAQ device and the PXIe controller or computer Application Time the time it takes for the PXIe controller or computer to analyze the acquired data and generate the AO stimulus Using Equation 2 1 and the Transfer Time from the sample system described in this section you can determine that an application time of 480 ys is required to close a 2 kHz control loop Application Time lt 500 us Transfer Time Application Time lt 500 us 20 us Application Time lt 480 us
34. ch as the NI PXIe 449x modules using Reference Clock Synchronization Reference Clock Synchronization With reference clock synchronization master and slave modules generate their ADC oversample clock from the shared 100 MHz reference clock from the PXIe backplane PXIe_CLK100 The backplane supplies an identical copy of this clock to each peripheral slot In addition multiple chassis can be synchronized by using a timing and synchronization board to lock the 100 MHz clock across chassis When you acquire data from multiple modules within the same NI DAQmx task NI DAQmx will automatically handle all of the Reference Clock Synchronization details required to synchronize the modules within the task This is known as a Multi Device Task To perform Reference Clock Synchronization when using multiple NI DAQmx tasks that are acquiring at the same rate complete the following steps to synchronize the hardware 1 Specify PXIe_CLK100 as the reference clock source for all modules to force all the modules to lock to the reference clock on the PXIe chassis 2 Choose an arbitrary NI PXIe 4339 master module to issue a sync pulse on one of the PXIe Trigger lines The sync pulse resets the ADCs and oversample clocks phase aligning all the clocks in the system to within nanoseconds 3 Configure the rest of the modules in your system to receive their sync pulse from the sync pulse master module This will ensure all ADCs are running in lockstep 4 C
35. e long it takes to receive data when starting an acquisition Since linear phase FIR filters are used in the digital filtering 1t is necessary to wait for the filter group delay to elapse after sending a sync pulse before the start trigger can be correctly handled in time Step 6 in the Reference Clock Synchronization section allows NI DAQmx to handle this delay automatically After the digital start trigger you cannot read data for the first sample in software until the digital filter group delay has elapsed Therefore it takes a total of twice the digital filter group delay to start an acquisition You can insert additional time between when the sync pulse occurs and when the start trigger occurs This will not affect the time it takes before samples are available after the start trigger which is always the group delay time Group delay time increases as sample rates decrease Refer to the MI PXTe 4339 Specifications document for details regarding the group delay at different sample rate Synchronization Some applications require tight synchronization between input and output operations on multiple modules Synchronization is important to minimize skew between channels or to eliminate clock drift between modules in long duration operations You can synchronize the analog input operations on two or more NI PXIe 4339 modules to extend the channel count for your measurements In addition the NI PXIe 4339 can synchronize with certain DSA modules su
36. e Factor specified by the gage manufacturer v Poisson s ratio defined as the negative ratio of transverse strain to axial strain longitudinal strain Poisson s ratio is a material property of the specimen you are measuring Vey Measured voltage of the bridge Vexy Excitation voltage provided by the NI PXIe 4339 Rpyotect 10 KQ resistor in series with the Shunt Cal A switch to protect against external fault voltages The total shunt cal resistance is equal to the Rsc and Rpyotect Series combination V Offset compensated ratiometric bridge output defined by the following equation r Note The ratio of the bridge output voltage and the excitation voltage is done internally on the NI PXIe 4339 Vg X ae 22223 d e O National Instruments 2 15 Chapter 2 Using the Module To convert module readings to strain use the following equation f 2V strain GFO v Full Bridge Type III This section provides information for the full bridge strain gage configuration type III The full bridge type HI only measures axial strain Figure 2 15 shows how to position strain gage resistors in an axial configuration Figure 2 16 shows the full bridge type HI circuit wiring diagram Figure 2 15 Full Bridge Type III Measuring Axial and Rejecting Bending Strain Measures Axial Rejects Bending A full bridge type III configuration has the following characteristics e Four active strain gage elements Tw
37. ed alias free bandwidth are used for sample rates lt 25 Hz This is done in order to reduce the large group delays associated with filtering at lower sample rates Refer to the NJ PXTe 4339 Specifications document for performance at lower rates 2 26 ni com NI PXle 4339 User Manual Filter Group Delay The digital filtering performed by the NI PXIe 4339 produces a delay of many samples worth of time between when an event occurs on the input signal going into the NI PXIe 4339 and when the data associated with that event is available at the output of the acquisition and filtering process This delay is called the group delay In order to simplify the process of acquiring data from the NI PXTe 4339 modules and correlating that data with data from other modules the NI PXIe 4339 compensates for this group delay in the following ways The Sample Clock output from the NI PXIe 4339 is generated at the point in time when the input signal is valid at the ADC input pins When acquiring data the NI PXIe 4339 generates a Sample Clock then waits for the data associated with that Sample Clock to be acquired then returns that data As a result any other acquisitions timed with this Sample Clock line up with the data returned by the NI PXIe 4339 e Any triggers generated or received by the NI PXIe 4339 are interpreted based on their relationship to the Sample Clock being generated For example a Start Trigger that starts an acquisition results in dat
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39. es and ratiometric mode is used to provide excitation and measure from bridge based sensors The programmable excitation block provides the excitation voltage for bridge based sensors The excitation voltage level is configurable on a per channel basis In ratiometric mode the excitation voltage is sensed locally or remotely via the remote sense terminals RS and RS and fed back to the ADC Analog to Digital Converter reference through a programmable gain amplifier The gain applied when sensing the excitation voltage is automatically selected based on the selected excitation voltage level and user specified input range Figure 2 18 NI PXle 4339 Signal Conditioning Block Diagram VO Connector Programmable Excitation EX Al Analog Reference Anti Alias Filter que ADE Al Gain 0 25 AO SCA SCA Te TEDS Interface x 8 Channels The bridge output voltage is sensed through the AI and AI pins and then amplified and filtered before being fed into the ADC input The ADC then performs a ratiometric measurement of the input signal versus the reference signal to determine the actual deflection of the bridge or sensor In voltage mode the ADC voltage reference is fed by a stable 2 5 V voltage source O National Instruments 2 23 Chapter 2 Using the Module The NI PXIe 4339 supports half quarter a
40. esereeseeseeesenenees 2 7 Figure 2 7 Half Bridge Type I Measuring Axial and Bending Strain coo 2 8 Figure 2 8 Half Bridge Type I Circuit Diagram 0 cee ceeseeeeeeeneeeceseneeeeeeees 2 9 Figure 2 9 Half Bridge Type II Rejecting Axial and Measuring Bending Strain 2 10 Figure 2 10 Half Bridge Type H Circuit Diagram ceecesseseeseeseeeceeeeeeeeeeeeeeees 2 11 Figure 2 11 Full Bridge Type I Rejecting Axial and Measuring Bending Strain 2 12 Figure 2 12 Full Bridge Type I Circuit Diagram ccccecessesceeeeeseeseeeeeteeeeeeeenees 2 13 Figure 2 13 Full Bridge Type II Rejecting Axial and Measuring Bending Strain 2 14 Figure 2 14 Full Bridge Type II Circuit Diagram ceeseseecesceseeeeeeeeeeeeeeees 2 15 Figure 2 15 Full Bridge Type HI Measuring Axial and Rejecting Bending Strain 2 16 vi ni com Figure 2 16 Figure 2 17 Figure 2 18 Figure 2 19 Figure 2 20 Figure 2 21 Figure 2 22 Figure 2 23 Figure 2 24 Figure 2 25 Figure 2 26 Tables Table 2 1 Table 2 2 Table 2 3 Table 3 1 NI PXle 4339 User Manual Full Bridge Type IM Circuit DiagraM ooooccnnnnnnnicinnonncnnnconcncnncnnnnconcnonos Force Pressure and Torque Sensor Circuit Diagram NI PXIe 4339 Signal Conditioning Block Diagram oonncnnnnnncinnncnn HWTSP Data Path Model 0 cece seceeereeecneeeeeeteees Transfer Time and Application Time Relationship Typical Control System i 2 3 ceive n a ie Input and Output of a Control Syste
41. f nature THE REMEDIES SET FORTH ABOVE ARE EXCLUSIVE AND THE CUSTOMER S SOLE REMEDIES AND SHALL APPLY EVEN IF SUCH REMEDIES FAIL OF THEIR ESSENTIAL PURPOSE EXCEPT AS EXPRESSLY SET FORTH HEREIN PRODUCTS ARE PROVIDED AS IS WITHOUT WARRANTY OF ANY KIND AND NI DISCLAIMS ALL WARRANTIES EXPRESSED OR IMPLIED WITH RESPECT TO THE PRODUCTS INCLUDING ANY IMPLIED WARRANTIES OF MERCHANTABILITY FITNESS FOR A PARTICULAR PURPOSE TITLE OR NON INFRINGEMENT AND ANY WARRANTIES THAT MAY ARISE FROM USAGE OF TRADE OR COURSE OF DEALING NI DOES NOT WARRANT GUARANTEE OR MAKE ANY REPRESENTATIONS REGARDING THE USE OF OR THE RESULTS OF THE USE OF THE PRODUCTS IN TERMS OF CORRECTNESS ACCURACY RELIABILITY OR OTHERWISE NI DOES NOT WARRANT THAT THE OPERATION OF THE PRODUCTS WILL BE UNINTERRUPTED OR ERROR FREE In the event that you and NI have a separate signed written agreement with warranty terms covering the products then the warranty terms in the separate agreement shall 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 prop
42. hat software compensation does not physically remove the offset of the bridge If the offset is large enough it limits the amplifier gain you can apply to the output voltage thus limiting the dynamic range of the measurement The NI PXIe 4339 does not have any internal hardware nulling circuitry however its input range is sufficiently wide so that the inputs will not saturate even with a relatively large initial bridge offset National Instruments A 1 NI Services National Instruments provides global services and support as part of our commitment to your success Take advantage of product services in addition to training and certification programs that meet your needs during each phase of the application life cycle from planning and development through deployment and ongoing maintenance To get started register your product at ni com myproducts As a registered NI product user you are entitled to the following benefits e Access to applicable product services Easier product management with an online account e Receive critical part notifications software updates and service expirations Log in to your National Instruments ni com User Profile to get personalized access to your services Services and Resources Maintenance and Hardware Services N helps you identify your systems accuracy and reliability requirements and provides warranty sparing and calibration services to help you maintain accuracy and mi
43. hoose one module to be the start trigger master This does not have to be the same module you chose in step 3 2 34 ni com 10 11 NI PXle 4339 User Manual Configure the rest of the modules in your system to receive their start trigger from the start trigger master module This ensures that all modules will begin returning data on the same sample Set the synchronization type of the Start Trigger slaves at DAQmx Trigger Advanced Synchronization Synchronization Type to Slave and that of the Master to Master Query DAQmx Timing More Synchronization Pulse Synchronization Time on all modules being synchronized choose the maximum value and set that as the DAQmx Timing More Synchronization Pulse Minimum Delay To Start on the module from which the synchronization pulse originates Commit all of the sync pulse slave module tasks using the DAQmxTaskControl VI Function This sets them up to expect the sync pulse from the master Commit the sync pulse master module task using the DAQmxTaskControl VI Function This will issue the sync pulse Start all of the start trigger slave module tasks This sets them up to expect the start trigger from the master Start the start trigger master module task You can now acquire data Q Tip Consider using a Multi Device task when synchronizing multiple devices at the same rate Q Tip You can find example VIs in the NI Example Finder Select Help Find Examples to launch the NI Example
44. igure 2 8 shows the half bridge type I circuit wiring diagram Figure 2 7 Half Bridge Type Measuring Axial and Bending Strain A half bridge type I has the following characteristics Two active strain gage elements One strain gage element is mounted in the direction of axial strain while the other acts as a Poisson gage and is mounted perpendicular to the principal axis of strain Halfbridge completion resistors R and R are provided by the NI PXIe 4339 e Sensitive to both axial and bending strain e Sensitivity 0 65 uV V per pe for GF 2 0 2 8 ni com NI PXle 4339 User Manual Figure 2 8 Half Bridge Type Circuit Diagram NI PXle 4339 Set Bridge Transducer TB 4339 B C Configuration to Half Bridge PL ama e At RA eww Ra e gage eo R ve gage e i WWW Ri i yms SCA i R i i WWW SOA WWW i AL Rsc The following symbols apply to the circuit diagram and equations R and R Half bridge completion resistors located inside the NI PXIe 4339 R Active element measuring compression from Poisson effect ve Rsc Shunt calibration resistor located inside the TB 4339 B C R Active element measuring tensile strain 8 R Lead resistance GF Gage Factor specified by the gage manufacturer v Poisson s ratio defined
45. lections in MAX and the LabVIEW Convert Strain Gage Reading VI Nyquist Frequency and Nyquist Bandwidth 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 2 This maximum frequency is known as the Nyquist frequency The bandwidth from 0 Hz to the Nyquist frequency is the Nyquist bandwidth ADC The NI PXIe 4339 ADCs use a conversion method known as delta sigma modulation This approach involves oversampling the input signal and then decimating and filtering the resulting data to achieve the desired sample rate Analog Input Filters The NI PXIe 4339 uses a combination of analog and digital filtering to provide an accurate representation of in band signals while rejecting out of band signals The filters discriminate between signals based on the frequency range or bandwidth of the signal The three important bands to consider are the passband the stopband and the alias free bandwidth The NI PXIe 4339 accurately represents signals within the passband as quantified primarily by passband flatness and phase nonlinearity All signals that appear in the alias free bandwidth are either unaliased signals or signals that have been filtered by at least the amount of the stopband rejection Anti Alias Filters A digitizer or ADC might sample signals containing frequency components above the Nyquist limit The
46. m with Bandwidth 22 kHz 2 29 Analog Level Trigger on Rising Slope ececeseesesceeceeceteeeeseeseeneene 2 32 Analog Edge Triggering with Hysteresis on Rising Slope 2 32 Analog Edge Triggering with Hysteresis on Falling Slope 2 33 Window Triggering oooocooccnccoccoocnononnnononnnnnonnnnnonnonn ono cnn corno non nc non nconnon conos 2 33 Front Connector Signal Pin Assignments omcocconcnncnconccnnanocncnnconcnncnncnnos 2 21 VO Connector Signal Descripti0NS 2 22 Wide Bandwidth Analog Output Nominal Gain 2 24 PXle DSTAR Line Descriptions oooocooccocnoocnononnnononnonncnncnnconcnnonnconconconos 3 2 O National Instruments vii Getting Started The NI PXIe 4339 has 24 bit resolution and supports sample rates from 1 S s to 25 6 kS s You can configure all settings on a per channel basis in software The channels support the following features e Voltage and ratiometric mV V measurements e Connecting sensors of all bridge configurations including quarter half and full bridge Quarter bridge configurations are supported with the TB 4339 B C Note For a complete list of terminal blocks supported by a specific release of NI DAQmx refer to the Readme available on the version specific download page or installation media e Balanced DC voltage excitation between 0 625 V and 10 V e Programmatic shunt calibration Shunt calibration resistors are p
47. maximum achievable acquisition rate without missing a sample is affected by both the transfer and application time Refer to Figure 2 20 1 Rate A A RO ee ee Max Transfer Time Application Time Note HWTSP can notify software if it cannot keep up with the acquisition rate Refer to the Hardware Timed Single Point Sample Mode topic in the NI DAQmx Help for more information 2 28 ni com NI PXle 4339 User Manual Figure 2 20 Transfer Time and Application Time Relationship Acquisition Rate Period Transfer Application Time Wait Time Idle 20 us N Next Sample Filter Group Delay 120 us Sample Sample Clock Clock Transfer time may vary depending on system 120 us is the approximate group delay of the 2 kHz filter for input frequencies lt 1 kHz passband of the filter Note For control applications it is important to consider the group delay of the data being acquired and analyzed when calculating the control system bandwidth Regardless of the sample rate the bandwidth of the system is as follows 1 bandwidth AAA aida Transfer Time Application Time Group Delay 2 kHz Control Loop Rate Calculation Example Figure 2 21 represents a typical control system in which you have a process to control a DAQ device to do the acquisitions and generate stimulus and a PXIe controller or computer to do the data processing and determine the proper AO value and returning it to the pro
48. n guide for signal locations on the terminal block 2 20 ni com NI PXle 4339 User Manual Table 2 1 Front Connector Signal Pin Assignments Front Connector Row Diagram Number Column A Column B Column C Channel 32 AIGND EX Al 31 SCA EX AL 0 Column A B G 30 SCA RS RS a aii 30 5 ja 29 AIGND EX AI 31 o o o 28 SCA EX AL 1 30 o o o 27 SCA RS RS Ae 2 e 26 AIGND EX A 28 o o o 27 3 5 25 SCA EX AL 2 26 o o o 24 SCA RS RS 25 Q Q 2 23 AIGND EX Al i eee 22 SCA EX AL 3 23 o o o 21 SCA RS RS 22 o o o 21 o o o 20 DGND TO T1 20 a o o 19 T4 T2 ES IO 18 T5 T6 T7 No 18 o o o 17 AOGND AO0 AOI Channel 17 o o o 16 o o o 16 AO4 AO2 AO3 15 o o o 15 AO5 AO6 AO7 0 Sh es 14 AIGND EX A 13 o o o 12 r 5 a 13 SCA EX AL 4 11 o o o 12 SCA RS RS 10 o o o 11 AIGND EX Al Ape 23 10 SCA EX AL 5 8 o o o 9 SCA RS RS F o o o 6 o o o 8 AIGND EX Al 5 o o a 7 SCA EX AL 6 Tale ae og 6 SCA RS RS 3 o o o 5 ro EX Al 2 o o o 1 o o o 4 SCA EX Al 7 Co 3 SCA RS RS 2 RSVD DGND RSVD No RSVD is reserved 1 RSVD RSVD RSVD Channel O National Instruments 2 21 Chapter 2 Using the Module I O Connector Signal Description Table 2 2 describes the signals found on the I O connector Table 2 2 I O Connector Signal Descriptions Signal Names Direction
49. nd full bridge measurements Half bridge completion and shunt calibration switches are provided on the NI PXIe 4339 Quarter bridge completion and shunt calibration resistors are provided on the TB 4339 B C terminal blocks AO is a single ended current limited external voltage fault protected copy of the front end gain stage Refer to the Wide Bandwidth Analog Output section for more information Each channel also provides a transducer electronic data sheet TEDS interface This interface can read the TEDS information from supported sensors to provide plug and play identification ofthe sensor and scaling information Wide Bandwidth Analog Output The wide bandwidth analog output voltage is a buffered version of the output of the first stage of the input signal chain The circuit consists of a unity gain differential to single ended stage with current limiting and external voltage fault protection The current limit is nominally 3 5 mA This circuit is always on and the gain is determined by configuration of the first stage The output state of the wide bandwidth analog output is undefined following power up Table 2 3 shows the nominal gain of the wide bandwidth analog output for the various input ranges of the module Table 2 3 Wide Bandwidth Analog Output Nominal Gain i Ratio Mode Input Range mV V Wide Bandwidth Voltage Mode Input Analog Output Gain Range V Vex gt 2 5 V Vex S 2 5 V 100 0 1 10 4
50. nimize downtime over the life of your system Visit ni com services for more information Warranty and Repair All NI hardware features a one year standard warranty that is extendable up to five years NI offers repair services performed in a timely manner by highly trained factory technicians using only original parts at a National Instruments service center Calibration Through regular calibration you can quantify and improve the measurement performance of an instrument NI provides state of the art calibration services If your product supports calibration you can obtain the calibration certificate for your product at ni com calibration 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 National Instruments B 1 Appendix B NI Services For information about other technical support options in your area visit ni com services Training and Certification The NI training and certification program is the most effective way to increase application development proficiency and productivity Visit ni com training for more information The Skills Guide assists you in identifying the proficiency requirements of your current application and gives you options for obtaining those skills consistent with your time and budget constraint
51. o strain gage elements are mounted in the direction of axial strain with one on one side of the strain specimen top while the other is on the opposite side bottom The other two act together as a Poisson gage and are mounted transverse perpendicular to the principal axis of strain with one on one side of the strain specimen top and the other on the opposite side bottom e Rejects bending strain e Sensitivity 1 3 pV V per ps for GF 2 0 2 16 ni com NI PXle 4339 User Manual Figure 2 16 Full Bridge Type III Circuit Diagram Transducer TB 4339 B C NI PXle 4339 Set Bridge Configuration to Full Bridge Al EX O Al EX SCA 2 Shunt SCA of Cal A WWW WW Rsc 1 Ferotect The following symbols apply to the circuit diagram and equations R Active element measuring compressive Poisson effect ve Rz Active element measuring tensile strain 8 R Active element measuring compressive Poisson effect ve R Active element measuring the tensile strain 8 R Lead resistance GF Gage Factor specified by the gage manufacturer v Poisson s ratio defined as the negative ratio of transverse strain to axial strain longitudinal strain Poisson s ratio is a material property of the specimen you are measuring Rsc Shunt calibration resistor loca
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53. pre trigger samples to be acquired Once enough pre trigger samples are acquired the reference trigger will occur the next time the analog trigger condition is met You also can route the resulting reference trigger event to supported digital terminals Refer to the device panels in MAX for additional information During repetitive triggering on a waveform you might observe jitter because of the uncertainty of where a trigger level falls 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 the NI PXIe 4339 modules for instance analog edge analog edge with hysteresis and window triggering National Instruments 2 31 Chapter 2 Using the Module Analog Edge Triggering For analog edge triggering configure the module to detect a certain signal level and slope either rising or falling Figure 2 23 shows an example of rising edge analog triggering The analog comparison becomes true when the signal starts below Level and then crosses above Level Figure 2 23 Analog Level Trigger on Rising Slope 3 2 MVN peste MI nnn iinan nnne ERSE Level Level and Slope of Signal Initiates Data Capture 0 Analog Comparison IO
54. r shunt calibration corrects for these errors and for errors caused by wire resistance within an arm of the bridge Shunt calibration is most useful with three wire quarter bridge sensors because there may be significant resistance in the wiring to the sensor and remote sense can not be used Refer to Figure 2 4 for a diagram of this setup The NI PXIe 4339 shunt calibration circuitry consists of a software controlled switch that is used in conjunction with the shunt calibration resistors provided on the TB 4339 B C terminal blocks Refer to the software help for information about enabling the shunt calibration resistors on the NI PXIe 4339 Shunt calibration involves simulating the input of a gage by changing the resistance of an arm in the bridge by some known amount This is accomplished by shunting or connecting a large resistor of known value across one arm of the bridge creating a known change in the bridge output This change is then measured and compared to the expected bridge output The result can be used to correct gain errors in the entire measurement path or to simply verify general operation in the setup National Instruments 2 3 Chapter 2 Using the Module Strain Gage Sensor Configurations This section describes the configurations and signal connection of various supported strain gage configuration types Quarter Bridge Type This section provides information for the quarter bridge strain gage configuration type I The qu
55. rom the date of invoice NI warrants that i its software products will perform substantially in accordance with the applicable documentation provided with the software and ii the software media will be free from defects in materials and workmanship If NI receives notice of a defect or non conformance during the applicable warranty period NI will in its discretion i repair or replace the affected product or ii refund the fees paid for the affected product Repaired or replaced Hardware will be warranted for the remainder of the original warranty period or ninety 90 days whichever is longer If NI elects to repair or replace the product NI may use new or refurbished parts or products that are equivalent to new in performance and reliability and are at least functionally equivalent to the original part or product You must obtain an RMA number from NI before returning any product to NI NI reserves the right to charge a fee for examining and testing Hardware not covered by the Limited Warranty This Limited Warranty does not apply if the defect of the product resulted from improper or inadequate maintenance installation repair or calibration performed by a party other than NI unauthorized modification improper environment use of an improper hardware or software key improper use or operation outside of the specification for the product improper voltages accident abuse or neglect or a hazard such as lightning flood or other act o
56. rovided on the TB 4339 B C terminal blocks Analog and digital filtering to reject out of band signals Remote sense of bridge excitation Installation Refer to the NI PXTe 4339 and TB 4339 B C Installation Guide and Terminal Block Specifications for step by step software and hardware installation instructions Module Specifications Refer to the NJ PXTe 4339 Specifications document for module specifications Module Accessories Refer to ni com scexpress for information about and a complete listing of supported accessories National Instruments 1 1 Using the Module This chapter describes how to connect Wheatstone bridge sensors to the NI PXIe 4339 in quarter half and full bridge configurations It also provides the I O connector signal pin assignments of the module Driver support for the NI PXIe 4339 was first available in NI DAQmx 14 2 For the list of devices supported by a specific release refer to the NI DAQmx Readme available on the version specific download page or installation media Connecting Signals This section includes a brief description of a general Wheatstone bridge and discusses how to connect the signals of supported strain gage configuration types It also discusses connecting leads for remote sensing and shunt calibration Refer to the NJ PXTe 4339 and TB 4339 B C Installation Guide and Terminal Block Specifications for more signal connection information Wheatstone Bridges Man
57. s and personal learning preferences Visit ni com skills guide to see these custom paths Nloffers courses in several languages and formats including instructor led classes at facilities worldwide courses on site at your facility and online courses to serve your individual needs Technical Support Support at ni com support includes the following resources Self Help Technical Resources 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 Software Support Service Membership the Standard Service Program SSP is a renewable one year subscription included with almost every NI software product including NI Developer Suite This program entitles members to direct access to NI Applications Engineers through phone and email for one to one technical support as well as exclusive access to online training modules at ni com self paced training NI also offers flexible extended contract options that guarantee your SSP benefits are available without interruption for as long as you need them Visit ni com ssp for more information Declaration of Conformity DoC A DOC
58. s modules automatically detect compatible accessories or terminal blocks The RSVD pins on the I O connector provide power to the accessories as well as digital communication lines This allows software to detect when accessories are inserted or removed In addition software can automatically identify the specific terminal block as well as access any calibration or scaling information associated with the terminal block MAX allows you to see what accessories are currently connected to your module In MAX expand Devices and Interfaces and locate your module Ifa terminal block is connected to your module it will be displayed beneath the module Unsupported terminal blocks appear in MAX with an X next to them NI DAQmx property nodes can be used to programmatically access information about connected accessories in your application Refer to the N DAQmx Help for documentation about programmatically accessing accessory status 2 36 ni com SC Express Considerations This chapter details the clock and trigger functionality available through the PXI Express chassis SC Express Clock and Trigger Signals PXle_CLK100 PXIe_CLK100 is a common low skew 100 MHz reference clock used for synchronization of multiple modules in a PXI Express measurement or control system The PXIe backplane is responsible for generating PXIe_CLK100 independently to each peripheral slot in a PXI Express chassis For more information refer to the PXT Express Specifi
59. stered of ARM Ltd or its subsidiaries LEGO the LEGO logo WEDO and MINDSTORMS are trademarks of the LEGO Group TETRIX by Pitsco is a trademark of Pitsco Inc FIELDBUS FOUNDATION and FOUNDATION are trademarks of the Fieldbus Foundation EtherCAT is a registered trademark of and licensed by Beckhoff Automation GmbH CANopend is a registered Community Trademark of CAN in Automation e V DeviceNet and EtherNet IP are trademarks of ODVA Go SensorDAQ and Vernier are registered trademarks of Vernier Software amp Technology Vernier Software amp Technology and vernier com are trademarks or trade dress Xilinx is the registered trademark of Xilinx Inc Taptite and Trilobular are registered trademarks of Research Engineering amp Manufacturing Inc FireWire is the registered trademark of Apple Inc Linux is the registered trademark of Linus Torvalds in the U S and other countries Handle Graphics MATLAB Real Time Workshop Simulink Stateflow and xPC TargetBox are registered trademarks and TargetBox and Target Language Compiler are trademarks of The MathWorks Inc Tektronix Tek and Tektronix Enabling Technology are registered trademarks of Tektronix Inc The Bluetooth word mark is a registered trademark owned by the Bluetooth SIG Inc The ExpressCard word mark and logos are owned by PCMCIA and any use of such marks by National Instruments is under license The mark LabWind
60. strain on one side of the strain specimen top while the other is mounted in the direction of bending strain on the opposite side bottom Half bridge completion resistors R and R are provided by the NI PXIe 4339 Sensitive to bending strain e Rejects axial strain e Sensitivity 1 V V per pe for GF 2 0 2 10 ni com NI PXle 4339 User Manual Figure 2 10 Half Bridge Type II Circuit Diagram NI PXle 4339 Set Bridge Transducer TB 4339 B C Configuration to Half Bridge wn SCA R i WWA fa 2A RL i The following symbols apply to the circuit diagram and equations R and R Half bridge completion resistors located inside the NI PXIe 4339 R Active element measuring compressive strain s Rsc Shunt calibration resistor located inside the TB 4339 B C R Active element measuring tensile strain 8 R Lead resistance GF Gage Factor specified by the gage manufacturer Ve Measured voltage of the bridge Viex Excitation voltage provided by the NI PXIe 4339 Rprotec 10 KO resistor in series with the Shunt Cal A switch to protect against external fault voltages The total shunt cal resistance is equal to the Rgc and Rpyotect series combination V Offset compensated ratiometric bridge output defined by the following equation 7 a dicten R A
61. ted inside the TB 4339 B C Vcu Measured voltage of the bridge Viex Excitation voltage provided by the NI PXIe 4339 Rprotec 10 KO resistor in series with the Shunt Cal A switch to protect against external fault voltages The total shunt cal resistance is equal to the Rsc and Rpyotect series combination V Offset compensated ratiometric bridge output defined by the following equation r Note The ratio of the bridge output voltage and the excitation voltage is done internally on the NI PXIe 4339 Vg X y Aa tia O National Instruments 2 17 Chapter 2 Using the Module To convert module readings to strain use the following equation o 27 strain e GF v 1 V v D Force Pressure and Torque Sensor Configurations The NI PXIe 4339 can be used with force sensors such as load cells pressure sensors or torque sensors that have the following characteristics e Wheatstone bridge based e Unamplified mV V or V V output These sensors typically use a full bridge configuration with a 350 Q nominal bridge resistance but other configurations and nominal bridge resistances can be used Figure 2 17 shows the force pressure torque sensor circuit diagram Figure 2 17 Force Pressure and Torque Sensor Circuit Diagram NI PXle 4339 Set Bridge Transducer TB 4339 B C Configuration to Full Bridge R AM a Ri b Shunt d Cal A MW el SCA
62. y sensors including strain gages load cells pressure sensors and torque sensors are based on the concept of a Wheatstone bridge There are four elements or legs in a Wheatstone bridge In general these elements can be resistive or reactive but in the majority of bridge based sensors the elements are resistive Most Wheatstone bridge based sensors use all four legs of the bridge as active sensing elements However common strain gage configurations include one two or four active sensing elements Figure 2 1 shows a resistive Wheatstone bridge circuit diagram Figure 2 1 Basic Wheatstone Bridge Circuit Diagram The Wheatstone bridge is the electrical equivalent of two parallel voltage divider circuits R and R compose one voltage divider circuit and R4 and R compose the second voltage divider circuit The output of a Wheatstone bridge is measured between the middle nodes of the two voltage dividers A physical phenomena such as a change in strain or temperature applied National Instruments 2 1 Chapter 2 Using the Module to a specimen changes the resistance ofthe sensing elements in the Wheatstone bridge resulting in a bridge output voltage that is proportional to the physical phenomena The output voltage of the bridge scales with the excitation voltage However the ratio of the bridge output Vc and the excitation voltage Vy remains fixed over variations in excitation voltage and it is this unitless ratio Vcy V gy

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