Hi The simple answer:
1) There are setups that increase the resolution of a counter 2) There are devices that are far more accurate at measuring frequency than a SR620 3) If you have three reasonably identical samples of a device you can indeed inter compare them once the resolution is there. Bob > On Dec 1, 2014, at 2:09 AM, Dr. David Kirkby (Kirkby Microwave Ltd) > <drkir...@kirkbymicrowave.co.uk> wrote: > > I think I have a flaw in my understanding of this. > > How can something like an SR620 measure the ADEV of an oscillator, if the > oscillator is of a similar or better than the reference fed into the SR620? > > I see plots of ADEV for hydrogen masers, but I can't understand how this > can be measured from the phase data unless the reference is better than the > DUT, which is not going to be possible with a good hydrogen maser. > > I was thinking it might be possible if one has 3 oscillators and 3 time > interval counters to perhaps solve 3 simultaneous equations. I can't prove > that, but it seems intuitively correct. > > I must be missing something! > > Also I have seen graphs of both Allan variance and Allen deviation. Both > are typically 10^-12 for a decent oscillator, but given the variance and > standard deviation are related by a square root, they can't both be around > 10^-12. I would expect to see values of 10^-6 or 10^-24, but I don't see > such dramatic differences from 10^-12. > > If I see numbers around 10^-12 on an OCXO, is that the Allen variance or > Allen Deviation? > > Dave > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
