Thanks Demetrios, that was a very interesting read. And thanks everyone else for responding. Cheers Michael On Sat, 18 Mar 2023 at 3:02 am, Demetrios Matsakis via time-nuts < time-nuts@lists.febo.com> 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 < > time-nuts@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 > >> _______________________________________________ > >> time-nuts mailing list -- time-nuts@lists.febo.com > >> To unsubscribe send an email to time-nuts-leave@lists.febo.com > > _______________________________________________ > > time-nuts mailing list -- time-nuts@lists.febo.com > > To unsubscribe send an email to time-nuts-leave@lists.febo.com > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-leave@lists.febo.com

On Thu, 16 Mar 2023 at 19:06, Michael Wouters via time-nuts < time-nuts@lists.febo.com> 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. > > Cheers > Michael I would have thought that if there were no systematic errors you could reduce the average error to zero with an infinite amount of samples. But a systematic error would prevent that. I don’t have an SR620, but it must have a maximum amount of averaging. I’m not a mathematician, but I if I had to take a guess, I would have thought that the average error would reduce as the square root of the number is samples. But (25/4)^2 is only 39, which is a lot less than the maximum averaging the instrument can do. It would be interesting to either find a formula, or even verify with a numerical simulation if I’m right about the square root relationship. I wonder if the 25 ps is based on a 95% (2 SD) confidence, 99.7% (3 SD) confidence or some other metric. -- Dr. David Kirkby, Kirkby Microwave Ltd, drkirkby@kirkbymicrowave.co.uk https://www.kirkbymicrowave.co.uk/ Telephone 01621-680100./ +44 1621 680100 Registered in England & Wales, company number 08914892. Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom

Hi The random errors have a standard deviation. The “one sigma” is often what is used to characterize them rather than the average. If they spec 10 ps resolution and that’s limited by the random stuff, they are talking about 10 ps one sigma . Bob > On Mar 19, 2023, at 9:27 AM, Dr. David Kirkby via time-nuts <time-nuts@lists.febo.com> wrote: > > On Thu, 16 Mar 2023 at 19:06, Michael Wouters via time-nuts < > time-nuts@lists.febo.com> 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. >> >> Cheers >> Michael > > > I would have thought that if there were no systematic errors you could > reduce the average error to zero with an infinite amount of samples. But a > systematic error would prevent that. I don’t have an SR620, but it must > have a maximum amount of averaging. > > I’m not a mathematician, but I if I had to take a guess, I would have > thought that the average error would reduce as the square root of the > number is samples. But (25/4)^2 is only 39, which is a lot less than the > maximum averaging the instrument can do. It would be interesting to either > find a formula, or even verify with a numerical simulation if I’m right > about the square root relationship. > > I wonder if the 25 ps is based on a 95% (2 SD) confidence, 99.7% (3 SD) > confidence or some other metric. > -- > Dr. David Kirkby, > Kirkby Microwave Ltd, > drkirkby@kirkbymicrowave.co.uk > https://www.kirkbymicrowave.co.uk/ > Telephone 01621-680100./ +44 1621 680100 > > Registered in England & Wales, company number 08914892. > Registered office: > Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United > Kingdom > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-leave@lists.febo.com