[time-nuts] HP53132A vs SR625

Bob Camp lists at rtty.us
Sat Mar 16 20:25:20 EDT 2013


Hi

The whole "how to align the SR-620's" thing has been gone over in great length (and very precisely) on the list. The bottom line is that Stanford's alignment procedure is not quite as good as it should / could be. 

Oddly enough, I don't remember seeing the residual offset in any brand new SR-620. I've only seen it on repaired units. My guess is that the factory tech's did a bit better alignment than the repair manual outlines.

Bob

On Mar 16, 2013, at 7:06 PM, Volker Esper <ailer2 at t-online.de> wrote:

> 
> 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 counters?
> 
> 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?
> 
> Cheers
> 
> Volker
> 
> 
> 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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>>   
> 
> 
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