Hi The counter is not the big issue in DMTD. We seem The problems lies elsewhere. I think we've gone into that pretty deeply in various recent threads.
As a practical bench instrument, the Pendulums are a very good choice. That's independent of anything having to do with DMTD. Bob On Feb 5, 2010, at 11:53 PM, Bruce Griffiths wrote: > Read the data sheet and the various application notes/white papers on the > Pendulum site. > The intrinsic resolution of the Pendulum counter (50ps) is slightly inferior > to that of the SR620 and HP5370A/B. > What they do is statistically process the results of a series of measurements > of the input phase taken at short intervals. > They actually fit a regression line to the resultant series of phase > measurements. > This process inherently filters out some of the noise of the counter. > If it were possible to do the same thing using an SR620 or HP5370 the noise > in the output resolution would be even lower. > > If one is building a conventional DMTD one doesn't actually need resolution > for the timestamping device/counter much better than 10ns or so to achieve a > resolution of around 1E-13/Tau with say a 100Hz beat frequency and 10MHz > inputs to the mixer/phase detector. > > Bruce > > Bob Camp wrote: >> Hi >> >> At least from what I've seen, the Pendulum's seem to work a bit better than >> the other counters you mention. That may simply be a function of their being >> designed much more recently. It could also be the issue of comparing beat >> up stuff on the bench to brand new stuff on the bench. The CNT-81 is rated >> to have a much better single shot time resolution than the others. >> >> Yes I realize that in no way addresses the question you asked. >> >> MDEV and ADEV measure slightly different things. Depending on what you are >> looking for MDEV may give you better insight. >> >> Bob >> >> >> On Feb 5, 2010, at 10:59 PM, Pete Rawson wrote: >> >> >>> Efforts are underway to develop a low cost DMTD apparatus with >>> demonstrated stability measurements of 1E-13 in 1s. It seems that >>> existing TI counters can reach this goal in 10s. (using MDEV estimate >>> or 100+s. using ADEV estimate). The question is; does the MDEV tool >>> provide an appropriate measure of stability in this time range, or is >>> the ADEV estimate a more correct answer? >>> >>> The TI performance I'm referring to is the 20-25 ps, single shot TI, >>> typical for theHP5370A/B, the SR620 or the CNT81/91. I have data >>> from my CNT81showing MDEV< 1E-13 in 10s. and I believe the >>> other counters behave similarly. >>> >>> I would appreciate any comments or observations on this topic. >>> My motivation is to discover the simplest scheme for making >>> stability measurements at this performance level; this is NOT >>> even close to the state-of-the-art, but can still be useful. >>> >>> Pete Rawson >>> >>> _______________________________________________ >>> 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. >>> >>> >> >> _______________________________________________ >> 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. >> >> > > > > _______________________________________________ > 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. > _______________________________________________ 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.
