[time-nuts] HP 5370B

Didier Juges didier at cox.net
Sat May 10 09:07:38 EDT 2008

> -----Original Message-----
> From: Magnus Danielson [mailto:magnus at rubidium.dyndns.org] 
> Sent: Saturday, May 10, 2008 5:09 AM
> To: time-nuts at febo.com; didier at cox.net
> Subject: Re: [time-nuts] HP 5370B
> From: "Didier Juges" <didier at cox.net>
> Subject: Re: [time-nuts] HP 5370B
> Date: Fri, 9 May 2008 20:11:42 -0500
> Message-ID: <005001c8b23a$cf4e6d90$0a01a8c0 at didierhp>
> > Mark,
> > 
> > The 5335 is specified at 9 digits/second of resolution, the 5370 is 
> > specified at 12 digits/second.
> That is severly overoptimistic on the 5370's part and just 
> about overoptimistic on the 5335's part. I think you should 
> not use those sales-numbers, as they are there to give you a 
> one-figure-of-merit hint, but they are not qualitative values.
> > That's 3 orders of magnitude better resolution. That brings 
> up noise 
> > that at 9d/s is simply negligible.
> I'd suspect something like 40 times better, not 1000 times better.
> The 5335 singel-shot resolution is 500 ps while the 5370 has 
> 25 ps, a factor of 20. The front-ends is not that good on the 
> 5335 thought, so let's add some noise there.
> I could make some tests if you like...
> > My two 5370s are rock stable if I only look at the 9 
> left-most digits.
> Maybe you should trim your multiplier chain?
> > While it would be nice to have the same stability at 12d/s 
> on the 5370 
> > as we get on the 5335 at 9d/s, that simply does not happen.
> I don't see how you could expect that. 10 digits stable 
> should be possible, but again it is just a very very rought 
> estimate of performance.
> Cheers,
> Magnus

Sorry if my answer was confusing. I did not mean to imply that the 5370 was
3 orders of magnitude more accurate than the 5335, simply that it attempts
to display data with 3 orders of magnitude greater resolution (3 orders of
magnitude more precise). The 5370 spec indicates 20 pS accuracy in
single-shot TI measurements, while it displays the data with 1 pS
resolution. In that mode, even with ideal signals coming in, there is
significant jitter on the displayed value.

That's a good illustration of the difference between precision and accuracy.

I think it shows where the limits of conventional technology lies. There are
a lot of 9 d/s counters, and most of those I have seen are perfectly stable
at that level. Some are even very simple and inexpensive. To get
significantly better requires exponentially more difficult technology, at
least considering what was available 20 years ago.

Didier KO4BB 

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