National Instruments SCXI-1120/D Calibration Procedure
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National Instruments SCXI-1120/D Calibration Procedure

National Instruments SCXI-1120/D Calibration Procedure

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CALIBRATION PROCEDURE
™
SCXI -1120/D
Introduction
What Is Calibration?
Why Should You Calibrate?
How Often Should You Calibrate?
™
™
National Instruments
, NI
, ni.com
are trademarks or trade names of their respective companies.
370268B-01
This document contains information and step-by-step instructions for
calibrating the National Instruments (NI) SCXI-1120 and SCXI-1120D
modules.
Calibration consists of verifying the measurement accuracy of a module
and adjusting for any measurement error. Verification is measuring the
performance of the module and comparing these measurements to the
factory specifications. During calibration, you supply and read voltage
levels using external standards, then you adjust the module calibration
circuitry. This circuitry compensates for any inaccuracies in the module,
and returns the accuracy of the module to the factory specifications.
The accuracy of electronic components drifts with time and temperature,
which can affect measurement accuracy as a module ages. Calibration
restores these components to their specified accuracy and ensures that the
module still meets NI standards.
The measurement requirements of your application determine how often
the SCXI-1120/D module needs to be calibrated to maintain accuracy.
NI recommends that you perform a complete calibration at least once every
year. You can shorten this interval to 90 days or six months based on the
demands of your application.
™
™
, and SCXI
are trademarks of National Instruments Corporation. Product and company names mentioned herein
© 2000, 2001 National Instruments Corp. All rights reserved.
September 2001

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Summary of Contents for National Instruments SCXI-1120/D

  • Page 1 National Instruments , NI , ni.com , and SCXI are trademarks of National Instruments Corporation. Product and company names mentioned herein are trademarks or trade names of their respective companies. 370268B-01 © 2000, 2001 National Instruments Corp. All rights reserved.

  • Page 2: Test Equipment

    Equipment and Other Test Requirements This section describes the test equipment, software, documentation, and test conditions required for calibrating the SCXI-1120/D modules. Test Equipment Calibration requires a high-precision voltage source with at least 50 ppm accuracy and a multiranging 5 1/2 digit digital multimeter (DMM) with 15 ppm accuracy.

  • Page 3: Test Conditions

    Maintain the temperature between 18–28 °C. • Keep relative humidity below 80%. • Allow a warm-up time of at least 15 minutes for the SCXI-1120/D module to ensure the measurement circuitry is at a stable operating temperature. Calibration The calibration procedure for the SCXI-1120/D module consists of the following steps: Set up the module for testing.

  • Page 4: Setting Up The Module

    Remove the cover on the module to access the potentiometers. 1 Grounding screw 2 Module cover Figure 1. Grounding Screw and Module Cover Removal Remove the side plate of the SCXI chassis. Install the SCXI-1120/D into slot 4 of the SCXI chassis. SCXI-1120/D Calibration Procedure ni.com...
  • Page 5 3 Side plate Figure 2. Side Plate Removal and Module Installation The SCXI-1120/D module does not need to be connected to a data acquisition (DAQ) device. Leave the configuration of the digital jumpers W41–W43 and W46 unchanged because they do not affect this procedure.
  • Page 6 To change the gain setting of a specified channel on the module, move the appropriate jumper on the module to the position indicated in Table 2. Refer to Table 1 for jumper reference designators, and Figure 3 for the location of the jumpers. SCXI-1120/D Calibration Procedure ni.com...
  • Page 7 5 Second-Stage Filter Jumpers 12 Terminal Block Mounting Hole 6 Rear Signal Connector 13 Grounding Screw Figure 3. SCXI-1120/D Parts Locator Diagram The SCXI-1120D module has an additional fixed pre-stage gain of 0.5. Note © National Instruments Corporation SCXI-1120/D Calibration Procedure...
  • Page 8 Configuring the Filter Jumpers Each input channel also has two user-configurable filter stages. The SCXI-1120 module ships in the 4 Hz position and the SCXI-1120/D module ships in the 4.5 kHz position. Refer to Table 3 or 4 to find the correct jumper setting for the desired cutoff frequency.
  • Page 9 Refer to the Setting Up the Module section for information on how to configure the channel filter and channel gain. Complete the following steps to verify the operation of the SCXI-1120/D module: Read the Test Conditions section in this document.
  • Page 10 For example, the positive input for channel 0 is pin A32, which is labeled CH0+. The negative input for channel 0 is pin C32, which is labeled CH0–. Table 5. SCXI-1120/D Front Connector Pin Assignments Pin Number Column A Column B...
  • Page 11 Table 5. SCXI-1120/D Front Connector Pin Assignments (Continued) Pin Number Column A Column B Column C RSVD RSVD MTEMP CHSGND DTEMP NP—No pin; NC—No connect Connect the DMM to the output of the same channel to which the calibrator was connected in step 5. Refer to Figure 4 to determine the pins on the 50-pin rear connector that correspond to the positive and negative outputs for the specified channel.
  • Page 12 45 46 47 48 49 50 Figure 4. SCXI-1120/D Rear Connector Pin Assignments Set the calibrator voltage to the value specified by the Test Point entry listed in Table 7 for the SCXI-1120 module or Table 8 for the SCXI-1120D module.
  • Page 13 0 ±3.0 mV. Refer to Figure 3 for the potentiometer location and Table 6 for the potentiometer reference designator. Table 6. Calibration Potentiometers Reference Designators Input Channel Number Input Null Output Null Set the channel gain on all channels to 1000.0. © National Instruments Corporation SCXI-1120/D Calibration Procedure...
  • Page 14 Verifying the Operation of the Module section. Verifying the adjusted values ensures the module is operating within its specifications after adjustments. If the SCXI-1120/D module fails after calibration, return it to NI for repair or Note replacement. SCXI-1120/D Calibration Procedure...

  • Page 15: Specifications

    –0.008840 –23.25 –4.686775 –4.613225 –4.689056 –4.610944 4.686353 4.613647 4.688626 4.611374 0.006138 –0.006138 0.008410 –0.008410 –9.3 –4.686353 –4.613647 –4.688626 –4.611374 4.65 4.691704 4.608296 4.693926 4.606074 0.011488 –0.011488 0.013710 –0.013710 –4.65 –4.691704 –4.608296 –4.693926 –4.606074 © National Instruments Corporation SCXI-1120/D Calibration Procedure...
  • Page 16 4.689464 4.610536 4.691936 4.608064 0.009248 –0.009248 0.011720 –0.011720 –0.02325 –4.689464 –4.610536 –4.691936 –4.608064 0.0186 4.689313 4.610687 4.692016 4.607984 0.009097 –0.009097 0.011800 –0.011800 –0.0186 –4.689313 –4.610687 –4.692016 –4.607984 0.0093 4.689443 4.610557 4.692731 4.607269 0.009227 –0.009227 0.012515 –0.012515 SCXI-1120/D Calibration Procedure ni.com...
  • Page 17 4.768769 4.531231 0.05 0.006720 –0.006720 0.077700 –0.077700 0.05 –93 –4.697789 –4.602211 –4.768769 –4.531231 46.5 4.698899 4.601101 4.841289 4.458711 0.007830 –0.007830 0.150220 –0.150220 –46.5 –4.698899 –4.601101 –4.841289 –4.458711 0.25 18.6 4.701669 4.598331 5.028819 4.271181 © National Instruments Corporation SCXI-1120/D Calibration Procedure...
  • Page 18 –0.530350 0.330350 –0.330350 –0.18 –5.070004 –3.929996 –4.870004 –4.129996 0.086 4.360392 4.239608 4.825892 3.774108 0.022500 –0.022500 0.488000 –0.488000 –0.086 –4.360392 –4.239608 –4.825892 –3.774108 0.038 3.879624 3.720376 4.810624 2.789376 0.039800 –0.039800 0.970800 –0.970800 –0.038 –3.879624 –3.720376 –4.810624 –2.789376 SCXI-1120/D Calibration Procedure ni.com...
  • Page 19 –0.006 –3.273770 –2.726230 –4.810770 –1.189230 1000 0.0029 3.416058 2.383942 4.895058 0.904942 1000 0.342000 –0.342000 1.821000 –1.821000 1000 –0.0029 –3.416058 –2.383942 –4.895058 –0.904942 Value available only when used with the SCXI-1327 high-voltage terminal block © National Instruments Corporation SCXI-1120/D Calibration Procedure...

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