Tom Van Baak wrote: > 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 > time-nuts@febo.com > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > Tom
Surely the time standard deviation should be: TDEV = TAU*MODADEV(TAU)/SQRT(3) ?? At least this appears to be so in the link you gave: http://www.wriley.com/paper2ht.htm Bruce _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts