Adjusting Voltage Excitation - National Instruments SCXI-1121 Calibration Procedure

This step calibrates the 10 V excitation level at the same time, but the accuracy
Note
achieved is limited to ±0.2%. To achieve better accuracy at the 10 V level, follow steps 1
through 4 but set the excitation level to 10 V instead of 3.333 V. If you do so, the 3.333 V
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 3.333 V.
SCXI-1121 Calibration Procedure
7. Adjust the input null potentiometer of channel 0 until the DMM
reading is 0.0 ±6.0 mV. Refer to Figure 3 for the potentiometer
location and Table 10 for the potentiometer reference designator.
8. Repeat steps 1 through 7 for the remaining analog inputs.
You have completed adjusting the analog input offsets.

Adjusting Voltage Excitation

When you adjust the excitation channels, always start with the voltage
excitation and then proceed to the current excitation. Use the voltage
excitation reference as the voltage reference for the current excitation.
Complete the following steps to adjust the voltage excitation:
Connect the 120 Ω resistor across the output of the excitation channel
1.
you are adjusting.
2. Configure the excitation channel to 3.333 V excitation level.
3. Set the DMM to voltage mode, and connect the DMM leads to the
excitation outputs as closely as possible to the resistor body.
4. Adjust the excitation voltage potentiometer until the voltage reading
falls between 3.334333 V and 3.331667 V. Refer to Figure 3 for the
potentiometer location and Table 11 for the potentiometer reference
designator.
Table 11. Excitation Calibration Potentiometer Reference Designators
Input Channel
Number
0
1
2
3
5. Repeat steps 1 through 4 for all remaining channels.
You have completed adjusting the voltage excitation channels.
Excitation Channel
Voltage Mode
R10
R20
R30
R40
14
Current Mode
R7
R17
R27
R37
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