[time-nuts] Picket fence ADEV measurement on 5370 counters

[Poul-Henning Kamp]

In message <PKEGJHPHLLBACEOICCBJCEGJCBAC.jmiles at pop.net>, "John Miles" writes:

>2) Something peculiar that my 5370B does: when the A-B time interval is
>about 60 milliseconds either side of coincidence, the counter fails to
>report a measurement at every other second.  E.g.:

I have done picket-fencing for years on my 5370B and never seen this
problem.

I usually use a 1Hz signal as start and a 10MHz from my house reference
as the stop.

I clock the HP5370B from a third source (usually the internal OCXO)
to avoid synchronicity.

I will caution you, that the IEEE488 implementation on the 5370B
is one of the more interesting I have encountered.

You can easily loose measurements, like what you see, by not being
ready when the counter is.

You should put the counter in talk mode, and have the computer continuously
in read mode to prevent this.

Also, you should timestamp the measurements in the computer with
fractional second granularity, there is a big difference between

	12:34:49
	12:34:50
	12:34:52
	12:34:53
	12:34:54

and
	12:34:49.985...
	12:34:50.995...
	12:34:52.005...
	12:34:53.015...
	12:34:54.025...

Poul-Henning

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Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
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