[time-nuts] Characterising frequency standards
Ulrich Bangert
df6jb at ulrich-bangert.de
Fri Apr 10 16:59:46 UTC 2009
Steve,
> So why would my counter show any significant differences
> between a 1 sec or 2 sec gate time?
suppose your source has a 0.5 Hz frequency modulation. Would you see it with
2 s gate time or a integer multiple of it? Would you notice it with 1 s gate
time or an odd integer of it?
> I've just done a Google search for "dead time correction
> scheme" and I just turn up results relating to particle
> physics where it seems measurements are unable to keep up
> with the flow of data, hence the need to factor in the dead
> time of system.
Google for the STABLE32 manual. THIS literature will bring you a lot
further, many well documented source examples in Forth and PL/1, hi. F.e.
you may look here:
http://www.wriley.com/
Best regards
Ulrich Bangert
> -----Ursprungliche Nachricht-----
> Von: time-nuts-bounces at febo.com
> [mailto:time-nuts-bounces at febo.com] Im Auftrag von Steve Rooke
> Gesendet: Freitag, 10. April 2009 12:55
> An: Discussion of precise time and frequency measurement
> Betreff: [!! SPAM] Re: [time-nuts] Characterising frequency standards
>
>
> Ulrich,
>
> 2009/4/10 Ulrich Bangert <df6jb at ulrich-bangert.de>:
> > Steve,
> >
> >> I think the penny has dropped now, thanks. It's
> interesting that the
> >> ADEV calculation still works even without continuous data
> as all the
> >> reading I have done has led me to belive this was sacrosanct.
> >
> > The penny may be falling but it is not completely dropped:
> Of course
> > you can feed your ADEV calculation with every second sample removed
> > and setting Tau0 = 2. And of course you receive a result
> that now is
> > in "harmony" with your all samples / Tau0 = 1 s
> computation. Had you
> > done frequency measurements the reason for this appearant
> "harmony" is
> > that your counter does not show significant different behaviour
> > whether set to 1 s gate time or alternate 2 second gate time.
>
> So why would my counter show any significant differences
> between a 1 sec or 2 sec gate time?
>
> > Nevertheless leaving every second sample out is NOT exactly
> the same
> > as continous data with Tau0 = 2 s. Instead it is data with
> Tau0 = 1 s
> > and a DEAD TIME of 1s. There are dead time correction schemes
> > available in the literature.
>
> I've just done a Google search for "dead time correction
> scheme" and I just turn up results relating to particle
> physics where it seems measurements are unable to keep up
> with the flow of data, hence the need to factor in the dead
> time of system. This form of application does not appear to
> correlate with the measurement of plain oscillators. Yes
> there is dead time, per say, but I fail to see how this can
> detract significantly from continuous data given a sufficient
> data set size (as for a total measurement time).
>
> I guess what we need is a real data set which would show that
> this form of ADEV calculation produces incorrect results, IE.
> the proof of the pudding is in the eating.
>
> 73,
> Steve
>
> > Best regards
> > Ulrich Bangert
> >
> >> -----Ursprungliche Nachricht-----
> >> Von: time-nuts-bounces at febo.com
> [mailto:time-nuts-bounces at febo.com]
> >> Im Auftrag von Steve Rooke
> >> Gesendet: Donnerstag, 9. April 2009 14:00
> >> An: Tom Van Baak; Discussion of precise time and frequency
> >> measurement
> >> Betreff: Re: [time-nuts] Characterising frequency standards
> >>
> >>
> >> Tom,
> >>
> >> 2009/4/9 Tom Van Baak <tvb at leapsecond.com>:
> >> > The first argument to the adev1 program is the sampling
> >> interval t0.
> >> > The program doesn't know how far apart the input file
> samples are
> >> > taken so it is your job to specify this. The default is 1 second.
> >> >
> >> > If you have data taken one second apart then t0 = 1.
> >> > If you have data taken two seconds apart then t0 = 2.
> >> > If you have data taken 60 seconds apart then t0 = 60, etc.
> >> >
> >> > If, as in your case, you take raw one second data and
> remove every
> >> > other sample (a perfectly valid thing to do), then t0 = 2.
> >> >
> >> > Make sense now? It's still "continuous data" in the
> sense that all
> >> > measurements are a fixed interval apart. But in any ADEV
> >> calculation
> >> > you have to specify the raw data interval.
> >>
> >> I think the penny has dropped now, thanks. It's
> interesting that the
> >> ADEV calculation still works even without continuous data
> as all the
> >> reading I have done has led me to belive this was sacrosanct.
> >>
> >> What I now believe is that it's possible to measure oscillator
> >> performance with less than optimal test gear. This will
> enable me to
> >> see the effects of any experiments I make in the future.
> If you can't
> >> measure it, how can you know that what your doing is good or bad.
> >>
> >> 73,
> >> Steve
> >> --
> >> Steve Rooke - ZL3TUV & G8KVD & JAKDTTNW
> >> Omnium finis imminet
> >>
> >> _______________________________________________
> >> time-nuts mailing list -- time-nuts at 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 at febo.com
> > To unsubscribe, go to
> > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> > and follow the instructions there.
> >
>
>
>
> --
> Steve Rooke - ZL3TUV & G8KVD & JAKDTTNW
> Omnium finis imminet
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
More information about the time-nuts
mailing list