Fluke PM6681 'fault' or 'characteristic'?
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
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@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
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Hi Ed,
Looks kind of reasonable. Signal level and slow phase-drift can
illustrate some interesting properties which is sometimes hidden.
You have cross-talk and that can interact in interesting ways. You
mention low signal levels, and well, this would be consistent with that.
You should square the signal up using gain, stage. See the Wentzel
approach, as being used at the clock input of the TAPR TADD-2 for instance.
Cheers,
Magnus
On 05/30/2017 04:54 AM, Ed Palmer 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
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.