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© National Instruments Corporation 3 NI PXI-5422 Calibration Procedure
What Is Calibration?
Calibration consists of verifying the output accuracy of a device and
correcting for any output error. Verification is measuring the performance
of a device and comparing the results to the specifications of the device.
NI calibrates every NI PXI-5422 at the factory. During the factory
calibration process, the calibration constants are stored in an onboard
EEPROM. These values are loaded from this EEPROM and used as needed
by the NI PXI-5422.
The NI PXI-5422 supports two types of calibration: self-calibration (or
internal calibration) and external calibration.
Self-Calibration
Self-calibration, also known as internal calibration, uses a software
command and requires no external connections. Self-calibration improves
output accuracy by compensating for variables, such as temperature and
time, that may have changed since the last external calibration.
Self-calibration retains the traceability of the external calibration.
External Calibration
External calibration is generally performed at either NI or a metrology lab.
This procedure replaces all calibration constants in the EEPROM and is
equivalent to a factory calibration at NI. Because the external calibration
procedure changes all EEPROM constants, it invalidates the original
calibration certificate. If an external calibration is done with a traceable
instrument, a new calibration certificate can be issued.
Why Should You Calibrate?
The accuracy of electronic components drifts with time and temperature,
which can affect output accuracy as a device ages. Calibration verifies
that the NI PXI-5422 still meets its specified accuracy and NI standards. If
adjustments are necessary, calibration makes the adjustments to restore
the accuracy.
How Often Should You Calibrate?
Self-calibration can be performed as necessary to compensate for
environmental changes.
Caution Although you can use self-calibration repeatedly, self-calibrating the
NI PXI-5422 more than a few times a day may cause excessive wear on the relays over
time.