Chapter 5
Using the SCXI-1521/B
©
National Instruments Corporation
5-13
Calibrating the SCXI-1521/B
The SCXI-1521/B is shipped with a calibration certificate and is calibrated
at the factory to the specifications described in Appendix A,
Calibration constants are stored inside the calibration EEPROM and
provide software correction values your application development software
uses to correct the measurements for errors in the module.
External Calibration
Most external calibration documents for SCXI modules are available to
download from
ni.com/calibration
by clicking
Manual Calibration
Procedures
. For external calibration of modules not listed there, Basic
Calibration Service or Detailed Calibration Service is recommended. You
can get information about both of these calibration services from
ni.com/
calibration
. NI recommends performing an external calibration once a
year.
Calibrating the System
You should perform offset null compensation or shunt calibration on
transducers in the system to improve accuracy. This is considered system,
or end-to-end, calibration.
Offset Null Compensation
Performing an offset null compensation removes offset in the measurement
system. Factors such as imperfections in the strain gauge, electrical offset
in the measurement system, signal leads with significant lead resistance, as
well as other system variables can create offset. Refer to the
, for information
about how to perform offset null compensation.
Shunt Calibration
Performing shunt calibration removes gain or amplitude errors in the
measurement system. Factors such as non-ideal gauge resistance and
temperature fluctuations, as well as other system variables can create these
errors. Refer to the
, for information about how to perform shunt calibration.