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National Instruments Corporation
15
SCXI-1121 Calibration Procedure
Adjusting Current Excitation
Complete the following steps to adjust the current excitation:
1.
Remove the resistor from the excitation channel if you have not
already done so.
2.
Configure the channel for 0.150 mA current excitation level.
3.
Set the DMM to current mode, and connect it to the excitation channel
output you want to adjust.
4.
Adjust the excitation current potentiometer until the current reading
falls between 0.150060 mA and 0.149940 mA. Refer to Figure 3 for
the potentiometer location and Table 11 for the potentiometer
reference designator.
Note
This step calibrates the 450 µA level at the same time, but the accuracy achieved is
limited to ±0.2%. To achieve better accuracy at the 450
μ
A level, follow steps 1 through 4
but set the excitation level to 450 µA instead of 150 µA. If you do so, the 150 µA 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 150 µA.
5.
Repeat steps 1 through 4 for all remaining channels.
You have completed adjusting the current excitation channels.
Verifying Adjusted Values
After completing the adjustments, it is important to verify the analog
input operation, the voltage excitation, and the current excitation again by
repeating the steps listed in the
. Verifying the
adjusted values ensures that the 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.
