[time-nuts] Re: Counter internal resolution error

[Demetrios Matsakis]

   On fact one of our best engineers concluded that there was leakage
   across the inputs, as Magnus mentioned.  I thought at the time he had
   measured it, but I am not 100% sure of that.

     On Mar 17, 2023, at 13:47, Magnus Danielson <magnus at rubidium.se>
     wrote:

   

     I also recall one paper relating to laser ranging measurement of the
     moon which also looked at temperature dependence of counters, and
     SR620 showed more sensitivity than some other counters. For some
     measurement purposes, the impact is less than for others.

     A fun experiment would be to use a delay-stepper to plot this. I
     accumulated equipment for that over the years, with increasing
     resolution and performance but never got around to it. Good little
     practical experiment now that I was able to steer the Colby DL10
     programmable trombone delay.

     There is two common reasons for non-linearity, one is from the
     interpolator itself where error-pulse shaper as well as
     pulse-to-voltage converter has non-linearities. Another one is du to
     leakage of either clock or other input shifts the trigger point due
     to lacking isolation. Such non-linearities can be handled through
     measurement setup and at times with averaging.

     Some properties can be managed through wise use of the
     autocalibration.

     Then again, most of the times I do not bother to go the extra
     stretch, but it is good to know the effects are there so one can
     consider them and if needed cope with them.

     So, time to close down computer, check out and leave Vancouver after
     a WSTS conference.

     Cheers,
     Magnus

   On 2023-03-17 16:57, Demetrios Matsakis wrote:

     I don’t know how SR counters are today, but when we were upgrading
     our infrastructure over a decade ago we found other counters had
     better linearity.  Rover et al’s open source article has a good
     discussion of these issues, although of course you need to have one
     if you are going to experiment.  See   G. D. Rovera, M. Siccardi, S.
     Romisch, and M. Abgrali, “Time delay measurements: estimation of the
     error budget”, Metrologia 56, 2019 035004

   On Mar 17, 2023, at 9:46 AM, Magnus Danielson via time-nuts
   [1]<time-nuts at lists.febo.com> wrote:

   Dear Michael,
   On 2023-03-16 08:17, Michael Wouters via time-nuts wrote:

     Dear time-nuts
     Counter specs often include an “internal resolution” error. For
     example,
     the SR620 specs say that it is 25 ps in single-shot, but this can be
     reduced to 4 ps with sufficient, repeated measurements. Can anyone
       offer
     any enlightenment as to the origin of this error, and the
     statistical
     distribution it has? I mentioned the SR620 but information about the
     53230A
     would be interesting too.

   First of all, the single-shot resolution is somewhat of a hallmark
   measure when it comes to counters.
   The interpolator resolution is part of this, but consider that there
   exists non-linearities in the interpolator which makes the error
   larger. I recall there being a plot of the non-linearity in the SR620
   manual.
   It is not uncommon to have interpolator resolution better than
   non-linearities, but the later may be more subtle to most.
   Averaging can help, but depending to specifics, it's hard to give a
   number.
   Cheers,
   Magnus

     Cheers
     Michael
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