Hi Yes, that's it exactly.
I knew we must be talking about to different things... Bob -----Original Message----- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Azelio Boriani Sent: Friday, October 05, 2012 5:25 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Best counter setting for ADEV? OK, now I understand: you are not interested in anything less than 100K seconds with your 1nS counter. Taking samples every 100K seconds from very stable sources with a 1nS counter hides the entire step between (for example) a 1E-14 and 2E-14. You can't see 1.1E-14, 1.2E-14, 1.3E-14 but, yes, you have a 1E-14 resolution at 100K seconds. On Fri, Oct 5, 2012 at 1:19 AM, Bob Camp <li...@rtty.us> wrote: > 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 <azelio.bori...@screen.it> > 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 <li...@rtty.us> 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: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] 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 <li...@rtty.us> 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: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] > 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 <li...@rtty.us> 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: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] > >> 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 <li...@rtty.us> 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: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] > >>> 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 <li...@rtty.us> 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 <ke...@rosenberg.net> > >>>> wrote: > >>>>>> > >>>>>>> On Oct 3, 2012, at 6:52 PM, Kevin Rosenberg <ke...@rosenberg.net > >>> > >>>>> wrote: > >>>>>>>> Nice plot! Yes, I'd have trouble measuring 10E-14 at 10E5 > >> seconds. > >>>>>>> > >>>>>>> Sorry, 1E-14 at 1E5. > >>>>>>> > >>>>>>> > >>>>>>> _______________________________________________ > >>>>>>> time-nuts mailing list -- time-nuts@febo.com > >>>>>>> To unsubscribe, go to > >>>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > >>>>>>> and follow the instructions there. > >>>>>> > >>>>>> > >>>>>> _______________________________________________ > >>>>>> time-nuts mailing list -- time-nuts@febo.com > >>>>>> To unsubscribe, go to > >>>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > >>>>>> and follow the instructions there. > >>>>>> > >>>>> _______________________________________________ > >>>>> time-nuts mailing list -- time-nuts@febo.com > >>>>> To unsubscribe, go to > >>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > >>>>> and follow the instructions there. > >>>>> > >>>>> > >>>>> > >>>>> _______________________________________________ > >>>>> time-nuts mailing list -- time-nuts@febo.com > >>>>> To unsubscribe, go to > >>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > >>>>> and follow the instructions there. > >>>>> > >>>> _______________________________________________ > >>>> time-nuts mailing list -- time-nuts@febo.com > >>>> To unsubscribe, go to > >>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > >>>> and follow the instructions there. > >>>> > >>>> > >>>> > >>>> _______________________________________________ > >>>> time-nuts mailing list -- time-nuts@febo.com > >>>> To unsubscribe, go to > >>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > >>>> and follow the instructions there. > >>>> > >>> _______________________________________________ > >>> time-nuts mailing list -- time-nuts@febo.com > >>> To unsubscribe, go to > >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > >>> and follow the instructions there. > >>> > >>> > >>> > >>> _______________________________________________ > >>> time-nuts mailing list -- time-nuts@febo.com > >>> To unsubscribe, go to > >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > >>> and follow the instructions there. > >>> > >> _______________________________________________ > >> time-nuts mailing list -- time-nuts@febo.com > >> To unsubscribe, go to > >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > >> and follow the instructions there. > >> > >> > >> > >> _______________________________________________ > >> time-nuts mailing list -- time-nuts@febo.com > >> To unsubscribe, go to > >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > >> and follow the instructions there. > >> > > _______________________________________________ > > time-nuts mailing list -- time-nuts@febo.com > > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
