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How Often Should You Calibrate?
Calibration Options: External Versus Internal
NI 6711/6713/6731/6733 Calibration Procedure
The measurement requirements of your application determine how often
the NI 6711/6713/6731/6733 must be calibrated to maintain accuracy.
NI recommends that you perform a complete calibration at least once every
year. You can shorten this interval to 90 days or six months based on the
demands of your application.
The NI 6711/6713/6731/6733 has two calibration options: an internal,
or self-calibration, and an external calibration.
Internal Calibration
Internal calibration is a much simpler calibration method that does not rely
on external standards. In this method, the device calibration constants are
adjusted with respect to a high-precision voltage source on the
NI 6711/6713/6731/6733. This type of calibration is used after the device
has been calibrated with respect to an external standard. However, external
variables such as temperature can still affect measurements. The new
calibration constants are defined with respect to the calibration constants
created during an external calibration, ensuring that the measurements can
be traced back to the external standards. In essence, internal calibration is
similar to the auto-zero function found on a digital multimeter (DMM).
External Calibration
External calibration requires using a high-precision DMM. During external
calibration, the DMM supplies and reads voltages from the device.
Adjustments are made to the device calibration constants to ensure that the
reported voltages fall within the device specifications. The new calibration
constants are then stored in the device EEPROM. After the onboard
calibration constants have been adjusted, the high-precision voltage source
on the device is adjusted. An external calibration provides a set of
calibration constants that you can use to compensate for the error in the
measurements taken by the NI 6711/6713/6731/6733.
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