[time-nuts] HP 5370B vs SR620

Chuck Harris cfharris at erols.com
Tue May 19 20:58:56 UTC 2009


There is an interesting application note on the differential linearity
issue. Apparently the problem was found by a Tektronix engineer, and HP
provided a correction to fix the problem in the 5370A.  That correction,
I believe, is available on Bama.

-Chuck Harris

Pete wrote:
> Roy,
> 
> The 5370s have a few quirks that you should know about to avoid
> possible surprises. These aren't newly discovered & have been the
> subject of various postings a few years ago.
> 
> 1) Both instruments have some front end coupling with the data path
>    & the timebase. This was mostly corrected in the 5370B.
> 2) Both instruments have a low level issue with non-linearity of the
>    interpolator which provides the ~20ps resolution.
> 
> The result of these imperfections is jitter readings taken on the 
> reference output signal (this is used in performance verification)
> will display the lowest readings you'll ever see. Real world signals
> locked to this source behave the same way. These readings are
> satisfying, but not real. When H-P spec'd the jitter floor at 30-
> 35ps, that's the true performance limit. Still quite good by any
> measure.
> 
> Another candidate counter you should check out is the Fluke/
> Pendulum PM6681. These aren't common, but sometimes are
> on *bay for reasonable ($500-600) prices. This is a much more versatile 
> instrument than the 5370s with lower front end
> noise, thus somewhat better jitter floor.
> 
> Regards,
> Pete Rawson
> 
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