11-19-2014 06:36 AM
Hi,
I have a question about the performance verification of the PXI 6608.
This is what I was able to perceive from the manual.
We have two modules:
CTR0: referenced to an external clock that has a minimum uncertainty of 0.75 ppb and generates a 400 s pulse to CRT1.
CTR1: is referenced to the internal 10 MHz OCXO and counts the number of cycles in that 400 s window: 400 * 10 MHz=4*10^9 . Any result different from this means an error.
Now to my understanding the performance verification is comparing the 10 MHz OCXO with the external clock. So by looking at the manual we have a uncertainty of 75ppb when the 10 MHz OCXO is on the slot 2: 0.75ppb * 10 MHz = +/- 0.75 Hz. BUT the performance verification assumes a tolerance of 0.1 Hz (10,000,000.1 < Hz < 9,999,999.9 Hz)
The calibration execute has the same approach as the performance verification,
Why does the PXI 6608 have a tolerance different from the manual?
Are we not testing the 10 MHz OCXO?