[time-nuts] Frequency Counter Errors

[Chris Albertson]

What happens if you feed the 10MHz external clock to the input.  If you
measure the reference frequency you should get 10MHz dead-on exact even if
the reference is not exactly 10MHz.     If you don't get this, the counter
has a problem.

I have seem my two counters disagree when I tried to measure the frequency
of an old Heatkit RF signal generator.   Turns out the problem
was because the RF sine wave was grossly not clean with much distortion on
the signal.  The two counters had their triggers set to different levels.

Test for triggering related problem by putting the signal into one counter
and then the marker output from the first counter in the the second
counter. This way only one trigger s used for both couters

On Wed, Mar 21, 2012 at 5:05 PM, Jerry Mulchin <jmulchin at cox.net> wrote:

> I have a question for the collective group.
>
> I have a HP 5372A and a HP 5328A frequency counters. Both counters use the
> same
> PRS-10 Rubidium frequency standard driving a 6 channel reference
> distribution amplifier
> to each counters reference input port. The problem is this;
>
> When I measure the same frequency on both counters, (done one at a time)
> the frequency
> is generally off by about 300 Hz or so between the counters. Now I would
> expect an error
> of +/- 1 digit, but 300Hz seems a bit strange to me. I can not find the
> problem and the
> difference exists even if I use the internal timebases of each counter,
> give or take the timebase errors.
> The frequency is always at least >200 to 300Hz off between the two
> counters and I don't know
> which one to believe. You know the "man with 2 clocks" problem.
>
> Anyone have any idea what may be causing this?
>
> Thanks
> Jerry
>
>
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-- 

Chris Albertson
Redondo Beach, California