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5
Calibration
This chapter discusses the calibration of the NI PXI-6683 and NI PXI-6683H.
Calibration consists of verifying the measurement accuracy of a device and correcting for any
measurement error. The NI PXI-6683 and NI PXI-6683H are factory calibrated before shipment
at approximately 25 °C to the levels indicated in Appendix A,
. The associated
calibration constants—the corrections that were needed to meet specifications—are stored in the
onboard nonvolatile memory (EEPROM). The driver software uses these stored values.
Factory Calibration
All NI PXI-6683 Series boards go through factory calibration. During that process the TCXO
frequency is adjusted so that it matches a reference 10 MHz atomic clock. A calibration constant
is then stored in on-board, non-volatile memory, along with other calibration metadata, such as
calibration date and temperature.
The calibration constant is used at start-up when the board is configured for free running mode.
When the NI PXI-6683 Series board is configured to use GPS, IEEE 1588, IRIG-B, or PPS as
its time reference, the TCXO frequency is adjusted according to the time reference and the
calibration constant is no longer used. If the board returns to free running mode, because it was
so configured or the time reference is no longer present, then the last applied TCXO voltage is
retained (it does not revert to the calibration constant).
Note
If the board is configured to use IEEE 1588 as time reference, and selected as
1588 Master through 1588's Best Master Clock algorithm, the board will be
free running and use its calibration constant.
Additional Information
Refer to
ni.com/calibration
for additional information on NI calibration services.