Brooke, Maybe this helps. The clock prediction into the future is based on the past history and the current point. If the measured ADEV for a clock is, say 1e-13, for a measurement interval of 1 day (tau), then the prediction, within one standard deviation, is that you'll be within 1e-13 tomorrow. 1e-13 at one day is about 9 ns. I think this is right. Can someone double check?
It shouldn't matter what your divider does -- 9 ns of time error is 9 ns regardless if it's the zero-crossing of a 5 MHz RF output of the leading edge of a 1PPS signal. A divider postpones cycle wrapping but doesn't affect clock accuracy or stability (other than the obvious introduction of passive & active component noise in the signal path). /tvb ----- Original Message ----- From: Brooke Clarke To: Tom Van Baak ; Discussion of precise time and frequency measurement Sent: Thursday, November 30, 2006 13:31 Subject: Re: [time-nuts] Predicting clock stability from thevariouscharacterizationmethods Hi Tom: Is there a way to use the Allan plot to predict the variation in a reading? For example if you use the plot comparing the 1 PPS from a GPS receiver to a good Cesium frequency standard, then: (1) what size of variation would you expect if the Cesium standard was divided down to 1 kHz and that was compared to the GPS 1 PPS, or (2) what size of variation would you expect if the Cesium standard was divided down to 1 Pulse/1,000 seconds? Have Fun, Brooke Clarke _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
