National Instruments SCXI-1141, SCXI-1142, SCXI-1143 Calibration Procedure

CALIBRATION PROCEDURE

™

SCXI -1141/1142/1143

This document contains the information and instructions needed to calibrate the SCXI-1141/1142/1143 using Traditional NI-DAQ (Legacy).

Calibrate the SCXI-1141/1142/1143 at a regular interval as defined by the measurement accuracy requirements of your application. NI recommends performing a complete calibration at least once every year. Based on your measurement accuracy needs, you can shorten this interval to 90 days or six months.

Conventions

The following conventions apply to this document:

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Software

Calibration requires the latest version of Traditional NI-DAQ (Legacy), which includes high-level function calls to simplify the task of writing software to calibrate devices. Traditional NI-DAQ (Legacy) supports many programming languages, including LabVIEW, LabWindows Microsoft Visual C++, Microsoft Visual Basic, and Borland C++.

If the SCXI-1141/1142/1143 is revision F or later, this procedure requires using a calibration software library. The library contains a function that is needed to adjust calibration circuitry on the module. If you do not have the software library files, you can download them from info code

exgpxj.

ni.com/info, using

The calibration software library consists of these files:

•

SCXIdpCal.dll

• SCXIdpCal.h

™

/CVI™,

Determine the revision of the SCXI-1141/1142/1143 by checking the part number

Note

of the module, which is located on the outside of the module case. For example, part number 182628C-01 is revision C.

SCXI-1141/1142/1143 Calibration Procedure 2 ni.com

Documentation

Test Equipment

The following documents are the primary references for writing your calibration utility:

• The Traditional NI-DAQ Function Reference Help includes information about the functions in Traditional NI-DAQ (Legacy).

• The DAQ Getting Started Guide provides instructions for installing and configuring NI-DAQ devices.

• The SCXI Quick Start Guide includes information for installing and configuring the SCXI chassis.

• The Traditional NI-DAQ User Manual includes information about creating applications that use Traditional NI-DAQ (Legacy).

You can add these help files when you install Traditional NI-DAQ (Legacy). After adding these help files, you can access them by selecting

Start»Programs»National Instruments NI-DAQ»Online-DAQ Support. The documents provide instructions about installing and

configuring DAQ devices. The documents also include detailed information about creating applications that use Traditional NI-DAQ (Legacy). For more information about the SCXI-1141/1142/1143, refer to the SCXI-1141/1142/1143 User Manual.

NI recommends using the equipment in Table 1 to verify and calibrate the SCXI-1141/1142/1143. If these instruments are not available, use the accuracy requirements listed to select a suitable substitute.

Table 1. Test Equipment

Recommended

Equipment

Calibrator Fluke 5700A 50 ppm

DMM NI 4060 5 1/2 digit, 15 ppm

DAQ Device NI 6030E 16-bit minimum

Terminal Block SCXI-1304 N/A

Model

Accuracy

Test Conditions

Follow these guidelines to optimize the connections and the environment during calibration:

• Keep connections to the SCXI terminal block and the rear connector of the SCXI module short. Long cables and wires act as antennae, picking up extra noise and thermal offsets that can affect measurements.

• Use shielded copper wire for all cable connections to the SCXI-1141/1142/1143. Use twisted-pair wire to reduce noise.

• Maintain the temperature between 18 and 28 °C.

• Keep relative humidity below 80%.

• Allow a warm-up time of at least 15 minutes for the SCXI module and 30 minutes for the DAQ device to ensure the measurement circuitry is at a stable operating temperature.

Calibration Procedure

This section provides step-by-step instructions for calling the appropriate calibration functions.

The steps used in the calibration procedure are as follows:

1. Setting up the SCXI-1141/1142/1143 for testing.

2. Verifying the existing operation of the SCXI-1141/1142/1143 to determine whether it is operating within its test limits.

3. Adjusting the offset and gain errors using a known external voltage source.

4. Verifying that the SCXI-1141/1142/1143 is operating within its test limits after adjustments.

Setting up the SCXI-1141/1142/1143 for Calibration

Complete the following steps, while referring to Figure 1 to set up the SCXI-1141/1142/1143 for calibration.

1. Make sure all components involved in the calibration procedure are powered-off.

2. Assemble the SCXI-1141/1142/1143, chassis, terminal block, and DAQ device as shown in Figure 1. The SCXI module you are calibrating must be connected directly to the DAQ device.

3. Power on the SCXI chassis and the external computer.

4. Make sure that all the appropriate driver and application software is installed.

SCXI-1141/1142/1143 Calibration Procedure 4 ni.com

5. You must configure the hardware properly with Measurement & Automation Explorer (MAX) under Traditional NI-DAQ (Legacy). Refer to the SCXI Quick Start Guide for details about configuring the SCXI chassis.

S C

X I

1 1

0 0

5 4 3 2 1

ADDRESS

M A

I N F

R A

M E

4345

1618

2123

91113

7 3 5 1

1 SCXI-1304 Terminal Block 2 SCXI-1141/1142/1143 Module 3 SCXI Chassis 4 SCXI-1349 Cable Adapter 5 Shielded 68-Pin Cable 6 NB1 Cable (50-Pin Ribbon Cable)

7 TBX 50-Pin Terminal Block 8 Cable to DMM 9 Cable to Calibrator 10 Calibrator 11 DMM 12 DAQ Device

Figure 1. Typical SCXI-1141/1142/1143 Setup for Calibration

Verifying the Operation of the SCXI-1141/1142/1143

The verification procedure determines how well the SCXI-1141/1142/1143 is meeting its specifications. You can use this information to select the appropriate calibration interval for your application.

Verifying Analog Input Measurements

Complete the following steps to verify the analog input offsets of the SCXI-1141/1142/1143:

1. Read the Test Conditions section in this document.

2. Refer to Table 9 for the specifications to test. Table 9 shows all acceptable settings for the module. NI recommends that you verify all ranges and gains. However, you can save time by checking only the ranges that your application uses.

3. Ensure that the E Series DAQ device is connected to the SCXI module.

4. Call

5. Call

6. Call

7. Call

8. Call

Calibrate_E_Series to minimize any uncertainty associated

with the E Series DAQ device. Set the following parameters:

• device—The Traditional NI-DAQ (Legacy) device number

assigned by MAX

• calOp—

ND_SELF_CALIBRATE

• setOfCalConst—ND_USER_EEPROM_AREA

• calRefVolts—0.0

MIO_Config to enable dithering on the E Series DAQ device

measurements. Set the following parameters:

• DAQdeviceNumber—The Traditional NI-DAQ (Legacy) device

number assigned by MAX

• dither—1

• useAMUX—0

SCXI_Single_Chan_Setup to configure the module for

single-channel measurements. Set the following parameters:

• SCXIchassisID—The chassis ID value obtained from MAX

• moduleSlot—1

• moduleChan—0

• DAQdeviceNumber—The cabled device number assigned by

MAX to the E Series DAQ device

SCXI_Set_Gain to configure the module to the gain value you

want to test. Set the following parameters:

• SCXIchassisID—The value obtained from MAX

• moduleSlot—1

• moduleChan—0

• gain—The gain value from Table 9 that you want to test

SCXI_Configure_Filter to disable the filter.

Set the following parameters: