Hello rorOttowa,
What exactly do you mean by the calibration period of the device? Are you refering to the amount of time after calibration that the device is considered calibrated? If so, the
PXI-4060 specifications specify the accuracy of the device at 24 hour, 90 day and 1 year points. After 1 year the device should go through calibration again to correct for loss of calibration.
National Instruments reccomends that you calibrate your device at least once a year, but if you wanted to maintain a higher level of accuracy you could calibrate your device more often.