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5
Calibration
This chapter discusses the SCXI-1120/D calibration procedures.
Calibration Equipment Requirements
For best measurement results, calibrate the SCXI-1120/D so that its offset
is adjusted to 0 ± 3 mV RTO and 0 ± 6 µV RTI. No special equipment is
needed other than a regular voltmeter with the following specifications:
•
Range: 30 mV to 300 mV
•
Resolution: 3.5 digits or greater
A multiranging 3.5-digit digital multimeter can provide you with the
necessary function as described previously. We will refer to the measuring
instrument as a digital multimeter (DMM).
Each channel on the SCXI-1120/D has two potentiometers dedicated for
calibration. One potentiometer is used to null the output offset; the other is
used to null the input offset.
Re-calibrate your SCXI-1120/D once a year.
Offset Null Adjust
To avoid erroneous results when nulling the amplifier, follow these steps in
the order indicated. To null the offset of the amplifier channels, complete
the following steps:
1.
Set the DMM range to the smallest range that can measure ±3 mV.
2.
Short the inputs of the DMM together and then to chassis ground.
3.
Record the measurement indicated by the DMM display. This is the
DMM inherent offset and it should be subtracted from subsequent
measurements.
4.
Short the desired channel inputs together and then to chassis ground.
5.
Set the amplifier gain to 1.