Adjustment Procedure; Adjusting Analog Input Offsets - National Instruments SCXI-1121 Calibration Procedure

Adjustment Procedure

© National Instruments Corporation
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
The adjustment procedure adjusts the analog input offsets, the voltage
excitation limits, and the current excitation limits.

Adjusting Analog Input Offsets

Complete the following steps to adjust the offset null value:
1. Set the channel gain on the channel you are adjusting to a gain of 1.
Set the filter value to 4 Hz.
2. Connect the calibrator to the analog input channel you want to adjust.
Refer to Table 13 to determine the pins on the 96-pin front connector
that correspond to the positive and negative inputs of the specified
channel. 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–.
3. Set the DMM to voltage mode, and connect it to the output of the same
channel to which the calibrator was connected in step 2. Refer to
Table 14 to determine the pins on the 50-pin rear connector that
corresponds to the positive and negative outputs for the specified
channel. For example, the positive output for channel 0 is pin 3, which
is labeled CH 0+. The negative output for channel 0 is pin 4, which is
labeled CH 0–.
4. Set the calibrator voltage to 0.0 V.
5. Adjust the output null potentiometer of the channel until the DMM
reading is 0.0 ±3.0 mV. Refer to Figure 3 for the potentiometer
location and Table 10 for the potentiometer reference designator.
Table 10. Calibration Potentiometers Reference Designators
Input Channel Number
0
1
2
3
6. Set the channel gain to a gain of 1000.0 on the channel you are
adjusting. Refer to Tables 3, 4, and 5 for more information.
Input Null
R02
R16
R26
R36
13
section.
Output Null
R03
R04
R05
R06
SCXI-1121 Calibration Procedure