[time-nuts] HP53132A vs SR625

Volker Esper ailer2 at t-online.de
Sat Mar 16 19:06:37 EDT 2013

What "small error" are we speaking about? The statement that SRS users 
have to tolerates a small error while HP users don't seems a little to 
general to me. IMHO we might be a bit more precise. Anyone who's already 
done an error analysis for - say - a 10MHz count and a comparison of the 

In real life every type of equipment has it's domain, where it has it's 
specific advantage. Could it be, that's the case for these counters, too?



Am 16.03.2013 19:57, schrieb Rick Karlquist:
>>> 1) I paid quite a bit of money and I had it "calibrated" and fixed by
>>> SRS,
>>> and it still exhibits a significant frequency offset with a "perfect"
>>> reference  and "perfect" DUT!!!
>>> SRS says a small frequency error is "normal", well that prevents me from
>>> using the unit as a frequency counter, for me it's only useful as a
>>> relative
>>> display frequency counter. HP doesn't have such a frequency error, so no
>>> worries there.
> I worked with the guy who designed the HP53132A.  He would
> never tolerate as "normal" a so-called small error.  The term
> "frequency counter" brings to mind something that digitally counts
> zero crossings and should never have an error.  First of all, even
> if that is all you do, it is still possible to screw it up.
> Secondly, "counters" have relied on analog interpolation even going
> back to the HP524 circa 1950.  There is no theoretical basis of having zero
> error in this case, but the idea is that you display the number of
> digits that are commensurate with the worst case accuracy of your
> interpolator.  Again, my colleague who designed the interpolator
> did very high quality work.  I am pleased to learn that our stuff
> is better than the stuff from the company up the road.
> Rick Karlquist N6RK
> HP Santa Clara Division 1979-1998
> (still working for Agilent!)
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