Programming instructions

Chapter 22 SCXI Calibration—Increasing Signal Measurement Precision
LabVIEW Data Acquisition Basics Manual 22-4
© National Instruments Corporation
SCXI Calibration Methods for Signal Acquisition
There are two ways you can calibrate your SCXI module—through
one-point calibration
or
two-point calibration
. The following illustration
explains why you may need to calibrate your SCXI module.
In this picture, you can see the difference between the ideal reading and the
actual reading. This difference is called V
os
, or the
binary offset
, before the
two readings intersect. The difference in slope between the actual and ideal
readings is called the
gain error
.
One-point calibration removes the V
os
(
binary offset
) by measuring a
0 volt signal and comparing the actual reading to it. Two-point calibration
removes the V
os
(
binary offset
)
and
corrects gain error by first performing
a one-point calibration. Then you measure a voltage at
x
volts and compare
it to the actual reading. The
x
must be as close as possible to the full-scale
range. The following sections explain how to perform a one-point and
two-point calibration.
Binary Reading
Binary Offset
Gain Error
V
os
Actual Voltage
in Binary Representation
Actual Reading
Ideal Reading