Programming instructions

Chapter 22 SCXI Calibration—Increasing Signal Measurement Precision
© National Instruments Corporation 22-5 LabVIEW Data Acquisition Basics Manual
One-Point Calibration
These steps show you how to perform a one-point calibration calculation in
LabVIEW. You should use one-point calibration when you only need to
adjust the binary offset in your module. If you need to adjust both the binary
offset and the gain error of your module, read the
Two-Point Calibration
section later in this chapter.
Note
If you are using an AT-MIO-16F-5, AT-MIO-64F-5, AT-MIO-16X device or
an E-series device, you should calibrate your DAQ device first using either the
MIO Calibrate VI or E-Series Calibrate VI.
1. Make sure you set the SCXI gain to the gain you want to use in your
application. If your modules have gain jumpers or DIP switches, they
must be set appropriately. Refer to your SCXI module user manual for
jumper or switch setting information. If your modules have
software-programmable gain, use the
input limits
parameter in the
AI Config VI to set gain.
2. Program the module for a single-channel operation by using the
AI Config VI with the channel that you are calibrating as the channels
parameter in the VI.
3. Ground your SCXI input channel to determine the binary zero offset.
You should ground inputs because offset can vary at different voltage
levels due to gain error. If you are using an SCXI-1100 or SCXI-1122,
you can ground your input channels without external hookups by
substituting the channel string with
calgnd
as the channel number.
For other modules, you need to wire the positive and negative channel
inputs together at the terminal block and wire them to the chassis
ground.