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National Instruments SCXI-1520 Calibration Procedure
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National Instruments SCXI-1520 Calibration Procedure

National Instruments SCXI-1520 Calibration Procedure

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CALIBRATION PROCEDURE
SCXI -1520
™
Equipment and Other Test Requirements
Test Equipment
If you do not have custom connection hardware, you need an SCXI-1314 terminal
Note
block and a shielded 68-pin connector cable. These components give easy access to the
individual pins on the SCXI-1520 front connectors. You also need an SCXI-1349 cable
adapter to connect the SCXI-1520 to the DAQ device.
Software and Documentation
This document contains information and step-by-step instructions for
calibrating the National Instruments SCXI-1520 module.
This section describes the equipment, software, documentation, and test
conditions required for calibrating the SCXI-1520.
Calibration requires a high-precision voltage source with at least 50 ppm
accuracy, a multiranging 5 1/2 digit digital multimeter (DMM) with
15 ppm accuracy, and a 16-bit data acquisition (DAQ) device.
NI recommends the following instruments for calibrating the SCXI-1520.
•
Calibrator—Fluke 5700A
•
DMM—NI 4060 or Agilent 34401A
•
16-bit DAQ device
If these instruments are not available, use the accuracy requirements listed
above to select a substitute calibration standard.
Use the following software and documentation to calibrate the SCXI-1520.
You can find them on the NI Web site at
•
The latest version of the NI-DAQ driver software
•
NI-DAQ Function Reference Help
.
ni.com/support

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Summary of Contents for National Instruments SCXI-1520

  • Page 1 Note block and a shielded 68-pin connector cable. These components give easy access to the individual pins on the SCXI-1520 front connectors. You also need an SCXI-1349 cable adapter to connect the SCXI-1520 to the DAQ device. Software and Documentation Use the following software and documentation to calibrate the SCXI-1520.

  • Page 2: Test Conditions

    NI-DAQ driver. These are your primary references for writing your calibration utility. For more information on the SCXI-1520, refer to the SCXI-1520 User Manual. Test Conditions Follow these guidelines to optimize the connections and the environment during calibration.
  • Page 3 Verifying that the device is operating within its specifications after adjustments. Setting Up the SCXI-1520 for Testing Complete the following steps to set up the SCXI-1520 for testing. Install the SCXI-1520 in slot 1 of the SCXI chassis. Using an SCXI-1349 cable adapter, connect a 68-to-68-pin cable between the SCXI-1520 module and the DAQ device installed in the host computer, as shown in Figure 1.
  • Page 4 DAQ device and the SCXI-1520. Verifying Gain and Offset Errors The verification procedure determines how well the SCXI-1520 module is meeting its specifications. You can use this information to select the appropriate calibration interval for your application.
  • Page 5 Set the following parameters: • SCXIchassisID—The value assigned by MAX • moduleSlot—1 Array notation: {X} denotes a one-element array initialized with the value X; [Y] denotes an uninitialized array of size Y. © National Instruments Corporation SCXI-1520 Calibration Procedure...
  • Page 6 Table 2. 15. Set the calibrator to output the test point voltage from Table 2. 16. Call to acquire the data. Set the following parameters: SCAN_Op • deviceNumber—The value assigned by MAX • numChans—{1} SCXI-1520 Calibration Procedure ni.com...
  • Page 7 EEPROM and can be read by application software and used for software correction. You cannot physically adjust the excitation on the SCXI-1520. If the measured values of the excitation fall outside the limits given in Table 3, the module is not ©...
  • Page 8 Read the Test Conditions section. Connect the DAQ device to the SCXI-1520 using an SCXI-1349 cable adapter and a 68-to-68-pin cable. Connect the DMM to the appropriate excitation output terminals, starting with channel 0. Refer to Table 1 to determine which pins on the 96-pin front connector correspond to the positive and negative excitation terminals of the specified channel.
  • Page 9 The Determining Gain Errors and Adjusting Calibration Constants sections explain how to determine the gain, offset, and excitation errors of the SCXI-1520 and how to adjust the calibration constants to correct for these errors. Determining Gain Errors Complete the following steps to determine the gain errors of the SCXI-1520.
  • Page 10 MAX • moduleSlot—1 • channel—The channel from step 7 • filterMode—0 • freq—0 • cutoffDivDown—0 • outClkDivDown—0 returns the actual cutoff frequency that SCXI_Configure_Filter the module uses as a 64-bit floating-point number, actualFreq. SCXI-1520 Calibration Procedure ni.com...
  • Page 11 • SCXIchassisID—The value assigned by MAX • moduleSlot—1 • channel—The channel number from step 7 • gain—The gain value you want to test. Refer to Table 2 for gain values and test points. © National Instruments Corporation SCXI-1520 Calibration Procedure...
  • Page 12 Gain Calibration Constants section. 23. Repeat steps 14 through 22 for the remaining gains you want to adjust on this module. 24. Repeat steps 7 through 23 for the remaining channels you want to adjust on this module. SCXI-1520 Calibration Procedure ni.com...
  • Page 13 2 and index is the index from Table 2 that corresponds to the gain you are adjusting Repeat steps 1 and 2 for the remaining gains and channels. © National Instruments Corporation SCXI-1520 Calibration Procedure...
  • Page 14 • moduleClass—2 • address—3 • numBytes—4 • data—The array that returns the value of the SCXI-1520 2.5 V reference voltage. The data is returned as 4 bytes in a 4-element array stored little-endian. • whichAccess—0 • regMethod— –1 •...
  • Page 15 Use –1 if the index corresponds to an empty slot. Use 51 if the index corresponds to a slot containing an SCXI-1520. © National Instruments Corporation SCXI-1520 Calibration Procedure...
  • Page 16 DAQ device Verifying Adjusted Values After completing the adjustments to the SCXI-1520, it is important that you verify the analog input operation by repeating the steps listed in the Verifying Gain and Offset Errors Verifying Voltage Excitation sections.
  • Page 17 SCB5 SCA4 SCA4 RSVD S5– RSVD RS5– RS5+ RSVD P5– RSVD SCA5 SCA5 SCB6 S6– SCB6 RS6– RS6+ SCB7 P6– SCB7 SCA6 SCA6 RSVD S7– RSVD RS7– RS7+ RSVD P7– RSVD SCA7 SCA7 © National Instruments Corporation SCXI-1520 Calibration Procedure...

  • Page 18: Specification Tables

    Specification Tables Table 2 contains the specifications you should use when verifying and calibrating the gain and offset of the SCXI-1520. If the module has been calibrated within the last year, the test point value should fall between the Lower Limit (V) Upper Limit (V) values.
  • Page 19 Table 2. SCXI-1520 Gain and Offset Calibration Table (Continued) Test Point (V) Gain Lower Limit (V) Upper Limit (V) Index –2.041670 –2.045375 –2.037958 1.814810 1.811519 1.818111 0.000000 –0.001481 0.001481 –1.814810 –1.818111 –1.811519 1.580650 1.577774 1.583516 0.000000 –0.001290 0.001290 –1.580650 –1.583516 –1.577774...
  • Page 20 Table 2. SCXI-1520 Gain and Offset Calibration Table (Continued) Test Point (V) Gain Lower Limit (V) Upper Limit (V) Index –0.490060 –0.490890 –0.489110 0.426090 11.5 0.425313 0.426861 0.000000 11.5 –0.000348 0.000348 –0.426090 11.5 –0.426861 –0.425313 0.376920 0.376238 0.377608 0.000000 –0.000308 0.000308...
  • Page 21 Table 2. SCXI-1520 Gain and Offset Calibration Table (Continued) Test Point (V) Gain Lower Limit (V) Upper Limit (V) Index –0.158060 –0.158352 –0.157777 0.136110 0.135864 0.136358 0.000000 –0.000111 0.000111 –0.136110 –0.136358 –0.135864 0.116670 0.116455 0.116879 0.000000 –0.000095 0.000095 –0.116670 –0.116879 –0.116455...
  • Page 22 Table 2. SCXI-1520 Gain and Offset Calibration Table (Continued) Test Point (V) Gain Lower Limit (V) Upper Limit (V) Index –0.037690 –0.037788 –0.037597 0.032670 0.032577 0.032756 0.000000 –0.000057 0.000057 –0.032670 –0.032756 –0.032577 0.027220 0.027139 0.027305 0.000000 –0.000056 0.000056 –0.027220 –0.027305 –0.027139...
  • Page 23 Table 2. SCXI-1520 Gain and Offset Calibration Table (Continued) Test Point (V) Gain Lower Limit (V) Upper Limit (V) Index –0.011670 –0.011731 –0.011603 0.008750 0.008689 0.008811 0.000000 –0.000052 0.000052 –0.008750 –0.008811 –0.008689 0.007540 0.007479 0.007598 0.000000 –0.000052 0.000052 –0.007540 –0.007598 –0.007479...
  • Page 24 *370396B-01* trademarks of National Instruments Corporation. Product and company names mentioned herein are trademarks or trade names of their respective companies. For patents covering National Instruments products, refer to the appropriate location: Help»Patents in your software, the patents.txt file on...