Chapter 5
Calibration
SCXI-1102/B/C User Manual
5-2
©
National Instruments Corporation
To calibrate the SCXI-1102/B/C module, you need a voltmeter with the
following specifications:
•
Accuracy
±
6 ppm standard reading
±
15 ppm sufficient reading
•
Range
–10 to +10 V
•
Resolution
8.5 digits
A multiranging 8.5-digit digital multimeter (DMM) can perform the
necessary calibrations.
To make sure that the DMM does not introduce an additional offset, you
can determine the offset error of the DMM by shorting its leads together
and reading the measured value. This value, the DMM offset, must be
subtracted from all subsequent measurements.
You will need to measure the module’s output between MCH0+ and
MCH0–. To access these pins, connect a 50-pin ribbon cable from the
CB-50 I/O connector block to the module rear signal connector or to the
rear signal adapter. Then connect to MCH0+ and MCH0– on the CB-50
pins 3 and 4, respectively.
Gain and Offset Calibration
To determine the offset and gain calibration factors of the
SCXI-1102/B/C module for a given gain, perform the following steps
for a two-point calibration. For two-point calibration, it is best to use
input voltages that correspond to the signal range of interest. For
example, if you are planning to measure bipolar voltages over the
module’s full input range, choose –9.9 V/G (negative full-scale) and
+9.9 V/G (positive full-scale) as your two input voltages.
1.
Select the desired channel. Set the channel gain to the desired gain.
2.
Apply the input for the first calibration point. To select negative
full scale as the calibration point, apply –9.9 V/G for an input
voltage.
a.
Apply the input voltage to the channel selected in step 1.
Note:
To make one of your calibration points the zero point, connect the positive
and negative channel leads to one of the chassis ground pins on the front
connector or terminal block.
b.
Measure the input voltage with the DMM. Call the measured
voltage
input1
.
