[time-nuts] HP 5370B
magnus at rubidium.dyndns.org
Sat May 10 14:26:37 EDT 2008
From: "Didier Juges" <didier at cox.net>
Subject: Re: [time-nuts] HP 5370B
Date: Sat, 10 May 2008 08:07:38 -0500
Message-ID: <007f01c8b29e$d337b740$0a01a8c0 at didierhp>
> 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.
You must recall that the 5370 is not a pure multiple of 1, 2 or 5 ps and this
requires additional digits for propper decimal representation.
Tossing up as much as 12 digits for a 1 s measurement while having about 20 ps
of resolution does not give 12 digits per second.
> 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.
I think you need to go even longer back in time for the 5370.
Advances have been made and 200 fs resolution have been manufactured. However,
those are ill suited for "normal" TI and frequency counter applications.
Achieving true 12 digits/s performance is possible but a bit challanging.
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