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This chapter discusses the calibration of the NI PXIe-6672.

Calibration consists of verifying the measurement accuracy of a device 
and correcting for any measurement error. The NI PXIe-6672 is 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.

The factory calibration of the NI PXIe-6672 involves calculating and 
storing four calibration constants. These values control the accuracy of 
four features of the device, which are discussed in the following sections.

The TCXO frequency can be varied over a small range. The output 
frequency of the TCXO is adjusted using this constant to meet the 
specification listed in Appendix A, 

. This calibration 

applies only to the NI PXIe-6672.

When using the PLL to lock PXI_CLK10 to an external reference clock, the 
phase between the clocks can be adjusted. The time between rising edges 
of PXI_CLK10 and the input clock is minimized using this constant.

To start the DDS reliably, the DDS start trigger must arrive within a certain 
window of time. The phase of the DDS start trigger is controlled by this 
constant to meet the setup and hold-time requirements of the DDS.