National Instruments 9235 Calibration Procedure
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National Instruments 9235 Calibration Procedure

National Instruments 9235 Calibration Procedure

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NI 9235/9236 Calibration Procedure
Contents
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This document contains information about calibrating National
Instruments 9235/9236 modules using NI-DAQmx. This calibration
procedure is intended for metrology labs.
This document does not discuss programming techniques or compiler
configuration. The NI-DAQmx driver contains online help files that have
compiler-specific instructions and detailed function explanations. You can
install these help files when you install NI-DAQmx on the calibration
computer.
Conventions ............................................................................................ 2
Software .................................................................................................. 2
Documentation ........................................................................................ 3
Calibration Interval ................................................................................. 3
Test Equipment ....................................................................................... 4
Test Conditions ....................................................................................... 4
Calibration Procedure ............................................................................. 5
Calibration Process Overview ......................................................... 5
Initial Setup...................................................................................... 5
Connecting the Calibrator to the Module ........................................ 6
Verification Procedures ................................................................... 8
Measurement Accuracy Verification........................................ 8
Shunt Calibration Accuracy Verification ................................. 12
Excitation Voltage Verification................................................ 16
Specifications .......................................................................................... 17
Test Limits .............................................................................................. 18
Calibrator Output ............................................................................. 18
Nominal Value ................................................................................. 18
1-Year Limits ................................................................................... 18
Where to Go for Support......................................................................... 20
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  • Page 1: Table Of Contents

    Deutsch ni.com/manuals This document contains information about calibrating National Instruments 9235/9236 modules using NI-DAQmx. This calibration procedure is intended for metrology labs. This document does not discuss programming techniques or compiler configuration. The NI-DAQmx driver contains online help files that have compiler-specific instructions and detailed function explanations.

  • Page 2: Conventions

    You must have the proper device driver installed on the calibration system before calibrating the device. Note NI recommends that you install the NI-DAQmx driver software before physically installing the NI 9235/9236. NI-DAQmx, available at , configures ni.com/downloads and controls the NI 9235/9236.

  • Page 3: Documentation

    NI Web site at ni.com/manuals Calibration Interval The NI 9235/9236 should be calibrated at a regular interval as defined by the measurement accuracy requirements of your application. National Instruments recommends that you routinely perform a complete calibration at least once every year.

  • Page 4: Test Equipment

    Test Equipment National Instruments recommends that you use the following equipment for calibrating the NI 9235/9236. Table 1. Recommended Equipment Equipment Recommended Model Requirements Calibrator Fluke 5500A If this instrument is unavailable, use a calibrator with generation of resistances in the ranges of 108 Ω – 132 Ω...

  • Page 5: Calibration Procedure

    DAQ device to calibrate. This document uses to refer to the device name. In the following procedures, use the device name as it dev1 appears in MAX. © National Instruments Corporation NI 9235/9236 Calibration Procedure...

  • Page 6: Connecting The Calibrator To The Module

    Connect the AUX HI terminal of the calibrator to the EXC1 terminal of the module. You do not have to change the EXC terminal connections for each channel you Note verify, because the EXC terminals all connect to a common excitation supply inside the NI 9235/9236. NI 9235/9236 Calibration Procedure ni.com...
  • Page 7 Refer to Figure 1 for an illustration of the calibrator to module connections. AUX HI EXC1 EXC0 Fluke 5500A NI 9235/9236 AUX LO Figure 1. Calibrator to Module Connections Refer to Figure 2 for the terminal assignments of the NI 9235/9236. EXC0 EXC1 EXC2 EXC3 EXC4 EXC5 EXC6 EXC7 Figure 2.

  • Page 8: Verification Procedures

    Set the calibrator resistance output to 120 Ω for the NI 9235 or 350 Ω for the NI 9236. Set the calibrator to operate mode (OPR). Wait one minute to allow the bridge elements formed by the calibrator and the module completion resistor to thermally stabilize.
  • Page 9 DAQmx_Val_Cfg_Default minVal: –0.027 maxVal: 0.027 units: DAQmx_Val_Volts bridgeConfig: DAQmx_Val_QuarterBridge voltageExcitSource: DAQmx_Val_Internal voltageExcitVal: for the NI 9235 for the NI 9236 useExcitforScaling: TRUE customScaleName: NULL * x refers to the channel number. © National Instruments Corporation NI 9235/9236 Calibration Procedure...
  • Page 10 NULL data: FALSE Start the acquisition using the DAQmx Start Task VI, as shown in the following table. LabVIEW Block Diagram NI-DAQmx Function Call Call with the DAQmxStartTask following parameter: taskHandle: taskHandle NI 9235/9236 Calibration Procedure ni.com...
  • Page 11 14. Perform the following calculation for each test result value other than 0 V/V, using the results you recorded in step 11. Test Result – 0 V/V Test Result © National Instruments Corporation NI 9235/9236 Calibration Procedure...

  • Page 12: Shunt Calibration Accuracy Verification

    × GF 1 where V is the compensated reading from the NI 9235/9236 and GF is a gage factor of 2. 16. Repeat steps 3 through 15 for all channels. 17. Set the calibrator to standby mode (STBY). 18. Disconnect the calibrator from the device.
  • Page 13 DAQmx_Val_Cfg_Default minVal: –0.027 maxVal: 0.027 units: DAQmx_Val_Volts bridgeConfig: DAQmx_Val_QuarterBridge voltageExcitSource: DAQmx_Val_Internal voltageExcitVal: for the NI 9235 for the NI 9236 useExcitforScaling: TRUE customScaleName: NULL * x refers to the channel number. © National Instruments Corporation NI 9235/9236 Calibration Procedure...
  • Page 14 NULL data: FALSE Start the acquisition using the DAQmx Start Task VI, as shown in the following table. LabVIEW Block Diagram NI-DAQmx Function Call Call with the DAQmxStartTask following parameter: taskHandle: taskHandle NI 9235/9236 Calibration Procedure ni.com...
  • Page 15 = result with shunt calibration enabled Result = result with shunt calibration disabled = wire resistance measured in step 1 wire = 120 Ω for the NI 9235 and 350 Ω for the NI 9236 comp © National Instruments Corporation NI 9235/9236 Calibration Procedure...

  • Page 16: Excitation Voltage Verification

    × GF 1 where V is the compensated reading from the NI 9235/9236 and GF is a gage factor of 2. 16. Repeat steps 3 through 15 for all channels. 17. Set the calibrator to standby mode (STBY). 18. Disconnect the calibrator from the device.

  • Page 17: Specifications

    Module (Gain Error) (Offset Error) NI 9235/9236 0.04% max 0.002% max * Range equals 29.4 mV/V. Table 3. NI 9235/9236 Shunt Calibration Accuracy Module Percent of Reading (Gain Error) NI 9235 0.22% max NI 9236 0.20% max Table 4. NI 9235/9236 Excitation Voltage Accuracy...

  • Page 18: Test Limits

    For accuracy verification, Upper Limits and Lower Limits are given in units of V/V for verification and units of με for reference. Table 5. NI 9235 Measurement Accuracy Verification Test Limits 1-Year Limits Calibrator Nominal...
  • Page 19 49,977.8 50,022.1 Note: The Upper and Lower Limit (V/V) values are commonly used for verification. The Upper and Lower Limit (με) values are for reference. Table 7. NI 9235/9236 Shunt Calibration Accuracy Verification Test Limits 1-Year Limits Nominal Nominal Lower...

  • Page 20: Where To Go For Support

    United Kingdom 44 (0) 1635 523545 CVI, LabVIEW, National Instruments, NI, ni.com, the National Instruments corporate logo, and the Eagle logo are trademarks of National Instruments Corporation. Refer to the Trademark Information at ni.com/trademarks for other National Instruments trademarks. The mark LabWindows is used under a license from Microsoft Corporation.

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