[time-nuts] Fluke PM6681 'fault' or 'characteristic'?

Azelio Boriani azelio.boriani at gmail.com
Tue May 30 06:10:46 EDT 2017

The assumption is that you are using the time interval measurement or
phase measurement. The PM6681 datasheet says that the time interval
range is from 0ns and the phase range from -180 to 360 deg, usually it
is best to avoid the zero degrees zone. Say that your test is another
evidence that managing phase coincidence is not trivial.

On Tue, May 30, 2017 at 4:54 AM, Ed Palmer <ed_palmer at sasktel.net> wrote:
> I was comparing my Sulzer 2.5 to my Efratom FRT and saw something very odd.
> I don't know if my PM6681 has developed a fault or if I'm just measuring two
> oscillators that are good enought to show oddities in my measurement system.
> When the phase of the two signals drifts through zero, the measurement gets
> noisy.  The levels are very low as you can see in the attached graph.
> Without the averaging, you can barely see anything.  But the degradation is
> significant.
> I've checked my counter and can't find anything wrong.  Power supplies are
> clean.  I've worked through the voltage tests and adjustments in the service
> manual.  Nothing was out of adjustment and nothing improved.
> Does this look like a fault or is it just another reason to avoid phase
> wraps and the dead zone around zero degrees?
> Thanks,
> Ed
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