On Mar 21, 7:36 pm, unruh <un...@invalid.ca> wrote: > On 2012-03-21, Alby VA <alb...@empire.org> wrote: > > > > > > > > > > > On Mar 21, 3:55?pm, unruh <un...@invalid.ca> wrote: > >> On 2012-03-21, David J Taylor <david-tay...@blueyonder.co.uk.invalid> > >> wrote: > > >> > "unruh" <un...@invalid.ca> wrote in message > >> >news:itmar.5841$yd7....@newsfe15.iad... > >> > [] > >> >> But -19 is about 2 microseconds if I understand it correctly. That means > >> >> that the clocks are incapable of delivering more than about 2 > >> >> microseconds of accuracy. What is you ?that last decimal digit of > >> >> accuracy in the offset is thus pure noise-- dominated by clock reading > >> >> noise. Why is it important for you then? > > >> > When I can see the decimal places, then I will know whether the precision > >> > estimate is reasonable. ?Just getting values such as -1, 0, 1 > >> > microseconds > >> > is insufficient to make that call. > > >> And how will the extra decimals help? The -19 was determined by making > >> successive calls to the clock and seeing how much it changed between > >> successive readings. That gives a good estimate of how long it takes to > >> make a call to the clock. Any precision in the answer beyond that is not > >> accuracy. I could give you the time to 60000 decimal places, each one of > >> the diffetent, but the last 5995 just being garbage (random numbers) > >> Would that tell yo uanything? > >> If for some reason you do not believe ntpd's estimation of your clock > >> accuracy, develope a better algorithm for determining it. It is a bug is > >> ntpd is reporting an accuracy much worse than it actually is. > > >> Ie, you have no data to make that call even if you get more digits. > > >> > David > > > unruh: > > > My take is the precision output might say your device is -19 so you > > know its > > accuracy is around 2/microseconds. But the offset several decimal > > places > > allows you to see its ever changing accuracy within that 2/microsecond > > band > > But that is not accuracy. That is presumably (if that -19 is accurate > and not a bug) is simply noise. If your measurement technique is only > good to 2us, then any additional precision is just noise. It may be fun > to see the noise, but not terribly useful. If it is not noise, then that > -19 is wrong, and one has a bug in the determination of the accuracy of > the clock reading. > > > to a greater detail than just -1, 0, or 1 microseconds. I guess its > > just a matter > > of getting more granular details for cool MRTG charting. :) > > It could well be that charting looks better without just bands on the > page. But is it worth it if that detail is just junk? It certainly is > not great art.
It there any good way to determine what is noise and what isn't? _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions