[time-nuts] Question about effect of sample interval on ADEV
Tom Van Baak
tvb at LeapSecond.com
Sun Jul 7 16:06:41 EDT 2013
Hi Bob,
Send me the raw data and I'll have a look to confirm or explain your results.
I've seen this in some of my FTS 1050 also; it's always been the fault of the battery charger circuit.
/tvb
----- Original Message -----
From: "Robert Darby" <bobdarby at triad.rr.com>
To: <time-nuts at febo.com>
Sent: Sunday, July 07, 2013 12:27 PM
Subject: [time-nuts] Question about effect of sample interval on ADEV
> This is a question that has probably been addressed on the list and in
> various texts but I've been unable to find an answer that I can fathom
> so here's a request for some info about the behavior of TimeLab (and
> probably all other similar programs).
>
> I have been trying to find the source of some periodic noise that
> appears when using a 5370B to measure an FTS 1050B against a 5065B. The
> noise manifests itself varying from 12s to 20s in a repetitive fashion.
> I asked C. Dawson about this and one of his suggestions was to try a
> longer sampling period. Down the rabbit hole I went!
>
> I ran four trials in succession at sample intervals of .07s, .25s, .5s,
> and 1s. The result is as if the adev ,modified, and Hadamard curves
> have been slid down and to the right along the noise floor of the 5370.
>
> My assumption, apparently incorrect, was that the software would take
> the sampling interval into account so that I would get essentially the
> same plot. When I edit a plot changing the sample interval, the trace
> remains essentially unchanged and this seems inconsistent with the
> results noted above. Can anyone explain in relatively simple terms what
> I'm missing?
>
> Thanks,
> Bob Darby
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