[time-nuts] Fluke PM6681 'fault' or 'characteristic'?
ed_palmer at sasktel.net
Mon May 29 22:54:13 EDT 2017
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
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?
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