Hmmm... If I measured a 10MHz oscillator for a 1/10 second, I could achieve, at best, 1ppm accuracy. Now my measuring system has a non accumulating error in the ms range, say <1s, so this would be totally unworkable. If I sampled for 1s, best would be .1ppm accuracy, but my measuring errors would still swamp the result. To make my measuring errors small, I could make the 1s overhead very small compared to the measing time period by, say, sampling for 10^6s thereby making the 1s error 1ppm. Now the 1s error is probably considerably smaller than that, probably by the order of at least a decade or two. If it was just .1s error, I could get a result to 1ppm in about a day and better if I sample of a number of days.
Cheers, Steve 2008/10/2 Scott McGrath <[EMAIL PROTECTED]>: > It depends on how accurately you want to measure the oscillator > frequency with your approach short term you probably would not be able > to measure the oscillator offset any better than a few parts in 10-5 > longer term probably a few parts in 10-7 might be possible as you > could compute the allen deviation and fit a curve through the median > values. > > NTP from a stratum 3 clock is only going to be precise to a few > milliseconds and for meaningful accuracy you need another order of > magnitude. This is part of the function of the drift file in xntpd > in which the daemon attempts to compensate for the drift and offset > inherent in cheap oscillators used in computer applications. > > > - Fellow nuts am I all wet here or have I missed a technique -- Steve Rooke - ZL3TUV & G8KVD Omnium finis imminet _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
