Hi Doing the repetition may give you a more fine grained idea of what the clocks are doing. It does not impact the resolution of the single measurement.
A single ns in 100,000 seconds is indeed 1.0x10^-14… Bob On Oct 4, 2012, at 6:11 PM, Azelio Boriani <[email protected]> wrote: > OK, because you think: (Y-X)/100K is the drift of the two clocks for each > second over 100K seconds and for each second I have a 1nS/100K resolution. > Now think about this: repeat the measure over and over and after each 100K > seconds you have your table. This table (your counter is 1nS) can have > figures like, say, 52nS, 53nS, 58nS, that is with a 1nS step. Your drift > maybe not exactly 52: it maybe 52.1 52.3 52.4 but you only see 52. So you > are loosing an entire nS between 52nS and 53nS. If you have a 100pS counter > you can see 52.0, 52.1 and so on. > > On Thu, Oct 4, 2012 at 10:13 PM, Bob Camp <[email protected]> wrote: > >> Hi >> >> If I have two clocks: >> >> 1) I know they are X ns apart at time = 0 >> 2) I know they are Y ns apart at time = 100,000 seconds >> 3) The resolution of the X and Y measurements is 1 ns >> >> I know the relative time between the two clocks to a lot better than >> 5.0x10^10... >> >> Bob >> >> -----Original Message----- >> From: [email protected] [mailto:[email protected]] On >> Behalf Of Azelio Boriani >> Sent: Thursday, October 04, 2012 3:43 PM >> To: Discussion of precise time and frequency measurement >> Subject: Re: [time-nuts] Best counter setting for ADEV? >> >> If you take 2 samples out of a 1nS counter than you can estimate your >> measure with a 500pS resolution (5E-10) with an uncertainty (noise) of >> 7E-10. >> >> On Thu, Oct 4, 2012 at 8:58 PM, Bob Camp <[email protected]> wrote: >> >>> Hi >>> >>> What if I only take two single measurements: >>> >>> One at time = 0, the other at time = 100,000 seconds. >>> >>> No averaging, no signal processing just two measurements. I look at the >>> time >>> difference between the two signals at time = 0, and then again a bit >> more >>> than a day later. >>> >>> Bob >>> >>> -----Original Message----- >>> From: [email protected] [mailto:[email protected]] On >>> Behalf Of Azelio Boriani >>> Sent: Thursday, October 04, 2012 2:48 PM >>> To: Discussion of precise time and frequency measurement >>> Subject: Re: [time-nuts] Best counter setting for ADEV? >>> >>> You're right: it is better to put it down correctly: >>> for a theoretical resolution of 10E-14@100K seconds, start with a 1nS >>> counter that takes 1 second samples for 100K seconds and average those >> 100K >>> samples. You have your resolution and a noise (an error bar) of 3E-12. If >>> you use a 100pS counter and do the same run, you will end up with a >> 10E-15 >>> reolution and 3E-13 noise, and so on. It turns out that to have a real >>> 10E-14 measure (@100K seconds), not blurred with noise, you must start >> with >>> a 10pS counter. >>> >>> On Thu, Oct 4, 2012 at 6:41 PM, Bob Camp <[email protected]> wrote: >>> >>>> Hi >>>> >>>> Maybe we're talking about two different things here. >>>> >>>> Simplistically, resolution is simply what the counter puts out as a >>> usable >>>> LSB. There are a lot of examples out there that will do a one >> nanosecond >>>> single shot measurement. That measurement includes the normal trigger >>> noise >>>> and "stuff" in the counter. There are a few assumptions about slew rate >>> of >>>> the input. >>>> >>>> If I take two one shot measurements spaced 100,000 seconds apart, my >>>> resolution over that period is 1.0x10^-14. The measurement is >>>> representative >>>> of what the sources have done to that level. Weather the sources are >>> stable >>>> to that level is independent of the resolution of the measurement. >>>> >>>> Bob >>>> >>>> -----Original Message----- >>>> From: [email protected] [mailto:[email protected]] >> On >>>> Behalf Of Azelio Boriani >>>> Sent: Thursday, October 04, 2012 12:27 PM >>>> To: Discussion of precise time and frequency measurement >>>> Subject: Re: [time-nuts] Best counter setting for ADEV? >>>> >>>> Yes, for a theoretical resolution of 10E-14@100K sec start with a 1nS >>> and >>>> average for 100K seconds but ending up with a noise (an error bar) of >>>> 3E-12. >>>> >>>> On Thu, Oct 4, 2012 at 4:25 PM, Bob Camp <[email protected]> wrote: >>>> >>>>> Hi >>>>> >>>>> For a *resolution* of 1.0 x 10^-14 at 1.0 x 10^5 seconds I only need >> a >>>> 1.0 >>>>> x >>>>> 10^-9 second reading out of the counter. Indeed, 5 or 10X more than >>> that >>>>> would be better if I was after a 1 x 10^-14 accuracy. >>>>> >>>>> Bob >>>>> >>>>> -----Original Message----- >>>>> From: [email protected] [mailto:[email protected]] >>> On >>>>> Behalf Of Azelio Boriani >>>>> Sent: Thursday, October 04, 2012 7:58 AM >>>>> To: Discussion of precise time and frequency measurement >>>>> Subject: Re: [time-nuts] Best counter setting for ADEV? >>>>> >>>>> Taking 10 samples from a 1nS counter leads you to a 100pS resolution >>> but >>>>> the noise at best (if it is really random) is reduced by SQRT(10). >> So, >>> as >>>>> already pointed out here, there is no real substitute for lower >> noise, >>>>> higher resolution measurements. >>>>> >>>>> On Thu, Oct 4, 2012 at 3:01 AM, Bob Camp <[email protected]> wrote: >>>>> >>>>>> Hi >>>>>> >>>>>> A 1 ns resolution TI counter will do the measuring part just fine. >>>>> Hitting >>>>>> the number, is where it gets a bit crazy. A *good* GPSDO might get >>> near >>>>>> that. >>>>>> >>>>>> Bob >>>>>> >>>>>> On Oct 3, 2012, at 8:56 PM, Kevin Rosenberg <[email protected]> >>>> wrote: >>>>>> >>>>>>> On Oct 3, 2012, at 6:52 PM, Kevin Rosenberg <[email protected] >>> >>>>> wrote: >>>>>>>> Nice plot! Yes, I'd have trouble measuring 10E-14 at 10E5 >> seconds. >>>>>>> >>>>>>> Sorry, 1E-14 at 1E5. >>>>>>> >>>>>>> >>>>>>> _______________________________________________ >>>>>>> time-nuts mailing list -- [email protected] >>>>>>> To unsubscribe, go to >>>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>>>> and follow the instructions there. >>>>>> >>>>>> >>>>>> _______________________________________________ >>>>>> time-nuts mailing list -- [email protected] >>>>>> To unsubscribe, go to >>>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>>> and follow the instructions there. >>>>>> >>>>> _______________________________________________ >>>>> time-nuts mailing list -- [email protected] >>>>> To unsubscribe, go to >>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>> and follow the instructions there. >>>>> >>>>> >>>>> >>>>> _______________________________________________ >>>>> time-nuts mailing list -- [email protected] >>>>> To unsubscribe, go to >>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>> and follow the instructions there. >>>>> >>>> _______________________________________________ >>>> time-nuts mailing list -- [email protected] >>>> To unsubscribe, go to >>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>> and follow the instructions there. >>>> >>>> >>>> >>>> _______________________________________________ >>>> time-nuts mailing list -- [email protected] >>>> To unsubscribe, go to >>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>> and follow the instructions there. >>>> >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >>> >>> >>> >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >>> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
