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National Instruments Corporation
7
NI 5421/5441 Calibration Procedure
External Calibration Options
External calibration involves both verification and adjustment. Verification
is the process of testing the device to ensure that the output accuracy is
within certain specifications. You can use verification to ensure that the
adjustment process was successful or to determine if the adjustment
process needs to be performed.
Adjustment is the process of measuring and compensating for device
performance to improve the output accuracy. Performing an adjustment
updates the calibration date, resetting the calibration interval. The device is
guaranteed to meet or exceed its published specifications for the duration
of the calibration interval.
This document provides two sets of test limits for most verification stages,
the
calibration test limits
and the
published specifications
. The calibration
test limits are more restrictive than the published specifications. If all of
the output errors determined during verification fall within the calibration
test limits, the device is guaranteed to meet or exceed its published
specifications for a full calibration interval (two years). For this reason,
you must verify against the calibration test limits when performing
verification after adjustment.
If all of the output errors determined during verification fall within the
published specifications, but not within the calibration test limits, the
device meets its published specifications. However, the device may not
remain within these specifications for another two years. The device will
meet published specifications for the rest of the current calibration interval.
In this case, you can perform an adjustment if you want to improve
the output accuracy or reset the calibration interval. If some output
errors determined during verification do not fall within the published
specifications, you must perform an adjustment to restore the device
operation to its published specifications.
The
section describes the recommended
calibration procedure. The
section describes
alternative procedures that allow you to skip adjustment if the device
already meets its calibration test limits or published specifications.
