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.
