This section discusses the calibration of the PXI-6683 and PXI-6683H.

Calibration consists of verifying the measurement accuracy of a device and correcting for any measurement error. The PXI-6683 Series are factory calibrated before shipment at approximately 25 °C to the levels indicated in the Specifications. 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 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-olvatile 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 PXI-6683 Series module is configured to use GPS, IEEE 1588, IEEE 802.1AS, 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 the time reference and is selected as the 1588 master with 1588's BMCA, the device will be free running and use its calibration constant.

Additional Information

Refer to ni.com/calibration for additional information on NI calibration services.