National Instruments SCXI-1121 Calibration Procedure
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National Instruments SCXI-1121 Calibration Procedure

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CALIBRATION PROCEDURE
SCXI -1121
™
Contents
This document contains information and instructions for calibrating the
National Instruments SCXI-1121 signal conditioning module.
Introduction ............................................................................................. 2
What Is Calibration? ........................................................................ 2
Why Should You Calibrate? ............................................................ 2
How Often Should You Calibrate? .................................................. 2
Software and Documentation.................................................................. 2
Test Equipment ....................................................................................... 3
Test Conditions ....................................................................................... 3
Calibration Process ................................................................................. 4
Initial Setup...................................................................................... 4
Configuring the Gain Jumpers.................................................. 7
Configuring the Filter Jumpers................................................. 8
Configuring the Excitation Jumpers ......................................... 9
Verification Procedure ..................................................................... 10
Verifying Analog Input Offsets ................................................ 10
Verifying Voltage Excitation Limits ........................................ 11
Verifying Current Excitation Limits......................................... 12
Adjustment Procedure...................................................................... 13
Adjusting Analog Input Offsets................................................ 13
Adjusting Voltage Excitation ................................................... 14
Adjusting Current Excitation.................................................... 15
Verifying Adjusted Values .............................................................. 15
Test Limits .............................................................................................. 16
SCXI-1121 Front and Rear Panel Diagrams........................................... 19

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Summary of Contents for National Instruments SCXI-1121

  • Page 1: Table Of Contents

    Verifying Voltage Excitation Limits ........11 Verifying Current Excitation Limits......... 12 Adjustment Procedure..............13 Adjusting Analog Input Offsets..........13 Adjusting Voltage Excitation ........... 14 Adjusting Current Excitation............ 15 Verifying Adjusted Values .............. 15 Test Limits ....................16 SCXI-1121 Front and Rear Panel Diagrams........... 19...

  • Page 2: Introduction

    NI standards. How Often Should You Calibrate? Calibrate the SCXI-1121 at a regular interval as defined by the measurement accuracy requirements of your application. NI recommends that you perform a complete calibration at least once every year. You can shorten this interval based on the accuracy requirements of your application.

  • Page 3: Test Equipment

    Maintain the ambient temperature between 18 °C and 28 °C. • • Keep relative humidity below 80%. • Allow a warm-up time of at least 15 minutes for the SCXI-1121 to ensure that the measurement circuitry is at a stable operating temperature. © National Instruments Corporation SCXI-1121 Calibration Procedure...

  • Page 4: Calibration Process

    Refer to Figure 1 for steps 1 and 2 and Figure 2 for steps 3 and 4. Remove the grounding screw from the SCXI-1121. Remove the cover on the SCXI-1121 so that you have access to the potentiometers. 1 Grounding Screw 2 Module Cover Figure 1.

  • Page 5: Configuring The Half-Bridge Completion Jumpers

    3 Side Plate Figure 2. Side Plate Removal and Module Installation You do not need to cable the SCXI-1121 to a DAQ device. Leave the configuration of the digital jumpers W32, W38, and W45 unchanged because they do not affect this calibration procedure.
  • Page 6 15 Half-Bridge Completion Jumpers 7 Rear Signal Connector 16 Input Null Adjust Potentiometers 8 Product Name, Assembly Number, Revision Letter 17 Excitation Mode Jumpers 9 SCXIbus Connector 18 Grounding Screw Figure 3. SCXI-1121 Parts Locator Diagram SCXI-1121 Calibration Procedure ni.com...

  • Page 7: Configuring The Gain Jumpers

    1, 10, 50, and 100. The second-stage gain provides gains of 1, 2, 5, 10, and 20. The SCXI-1121 ships with the first-stage gain set to 100 (position A) and the second-stage gain set to 10 (position D).

  • Page 8: Configuring The Filter Jumpers

    Configuring the Filter Jumpers Each input channel also has two user-configurable filter stages. The SCXI-1121 ships in the 4 Hz position. Refer to Table 5 for the correct jumper setting for the desired cutoff frequency. Refer to Figure 3 for the locations of the jumper blocks on the SCXI-1121.

  • Page 9: Configuring The Excitation Jumpers

    Set both jumpers in the same mode for correct operation of the excitation channel. Refer to Table 6 to determine how to set up the SCXI-1121 in the desired mode. The SCXI-1121 ships to you in the voltage mode.

  • Page 10: Verification Procedure

    In the voltage mode—3.333 V or 10 V After selecting the excitation mode of the desired operation—voltage or current, refer to Table 7 to set the SCXI-1121 for the level of operation. The SCXI-1121 ships with the voltage mode set to 3.333 V.

  • Page 11: Verifying Voltage Excitation Limits

    SCXI-1121. Refer to Table 12 for available gains. Set the channel filter for all channels on the SCXI-1121 to 10 kHz. Connect the calibrator to the analog input channel you are testing, starting with channel 0.

  • Page 12: Verifying Current Excitation Limits

    Compare the DMM reading to the limits for excitation shown in Table 8. If the reading falls between the Upper Limit and the Lower Limit values, the SCXI-1121 passed the test. Table 8. SCXI-1121 Voltage Excitation Limits Test Point (V)

  • Page 13: Adjustment Procedure

    You have completed verifying the current excitation limits. If any of your measurements fall outside the limits listed in Table 9, adjust the SCXI-1121 as described in the Adjusting Current Excitation section. Adjustment Procedure The adjustment procedure adjusts the analog input offsets, the voltage excitation limits, and the current excitation limits.

  • Page 14: Adjusting Voltage Excitation

    4 but set the excitation level to 10 V instead of 3.333 V. If you do so, the 3.333 V level of this channel will then be calibrated to ±0.2% instead of to ±0.04%. In the factory, the SCXI-1121 is calibrated for 3.333 V. Repeat steps 1 through 4 for all remaining channels.

  • Page 15: Adjusting Current Excitation

    SCXI-1121 is operating within its test limits after adjustments. Note If the SCXI-1121 fails after calibration, return it to NI for repair or replacement. For more information about how to contact NI for repair or replacement, refer to the Technical Support Information document.

  • Page 16: Test Limits

    Test Limits Table 12 contains test limits for the SCXI-1121. If the module was calibrated within the last year, the output should fall between the Upper Limit and Lower Limit values. Table 12. SCXI-1121 Test Limits 4 Hz Filter Setting...
  • Page 17 Table 12. SCXI-1121 Test Limits (Continued) 4 Hz Filter Setting 10 kHz Filter Setting Upper Lower Upper Lower Gain Test Point (V) Limit (V) Limit (V) Limit (V) Limit (V) 0.9000 4.534293 4.465707 4.535706 4.464294 0.0000 0.005142 –0.005142 0.006555 –0.006555 –0.9000...
  • Page 18 Table 12. SCXI-1121 Test Limits (Continued) 4 Hz Filter Setting 10 kHz Filter Setting Upper Lower Upper Lower Gain Test Point (V) Limit (V) Limit (V) Limit (V) Limit (V) 2000 0.00000 0.022238 –0.022238 0.029480 –0.029480 2000 –0.00225 –4.448611 –4.551389 –4.441369...

  • Page 19: Scxi-1121 Front And Rear Panel Diagrams

    SCXI-1121 Front and Rear Panel Diagrams Table 13 shows the pin assignments for the SCXI-1121 front panel connector. Table 14 shows the pin assignments for the SCXI-1121 rear signal connector. © National Instruments Corporation SCXI-1121 Calibration Procedure...
  • Page 20 Pin Number Column A Column B Column C CH0+ CH0– Column EX0+ EX0– EGND0 CH1+ CH1– EX1+ EX1– EGND1 CH2+ CH2– EX2+ EX2– EGND2 CH3+ CH3– EX3+ EX3– EGND3 RSVD SCAL RSVD MTEMP NC—No Connection CGND DTEMP SCXI-1121 Calibration Procedure ni.com...
  • Page 21 Connection RSVD—Reserved 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.

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