Hi The math is pretty straightforward.
Let's say the clock is 10 MHz, that's 100 ns. Say a handful is 5 +/- 3 (2 to 8) Your measure will bounce up and down by 6x100 ns = 600 ns. Over a 100 second period that's going to be 6.0 x10^-9 bounce in the data. If you run a 100 second loop as well, that's the noise in the loop (just from one source). Six times faster clock, you get 1.0x10^-9. Step up the "handful" for the faster clock's pipeline and you may be back at the same place. Take a bunch of readings (you only get one a second) and average - things get better by square root of the samples. That's IF you have enough jitter / dither in the system to smooth things out. If you have "lumpy" noise (as is often the case with interrupts) you may get very little gain from averaging. With a 100 second loop, a TBolt is doing sub 1x10^-11, so you are at least 100X worse. Bob On Dec 6, 2012, at 5:57 PM, Chris Albertson <albertson.ch...@gmail.com> wrote: > You'd have to seriously divide down the output from the 10MHz OCXO if you > were going to use it as an interrupt. Maybe to divide by 10,000? and even > at the higher clock rate you'd still have poor resolution. > > I image each interrupt handler would sample some internal counter and the > background task would look at the delta between the two and adjust the DAC > to drive the OCXO to close the difference. The resolution would be > (maybe?) a "handful" of clock cycles. Given enough time, say a 1000 > second period it might wrk well enough. I can't know without doing a more > detailed design > > > On Thu, Dec 6, 2012 at 1:59 AM, Don Latham <d...@montana.com> wrote: > >> Chris: >> >>> The question I have again is about a simple phase detector. >> >> I did ask if the arduino interrupt ports could be used as a phase >> detector; one on the GPS and one on the OXCO. Too much jitter? If the 12 >> MHz clock is too slow, would an 80 MHz clock ARM arduino style processor >> work? I'm simply too new at this to decide. >> >> Don >> >> -- >> "Neither the voice of authority nor the weight of reason and argument >> are as significant as experiment, for thence comes quiet to the mind." >> De Erroribus Medicorum, R. Bacon, 13th century. >> "If you don't know what it is, don't poke it." >> Ghost in the Shell >> >> >> Dr. Don Latham AJ7LL >> Six Mile Systems LLP >> 17850 Six Mile Road >> POB 134 >> Huson, MT, 59846 >> VOX 406-626-4304 >> www.lightningforensics.com >> www.sixmilesystems.com >> >> >> >> _______________________________________________ >> 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. >> > > > > -- > > Chris Albertson > Redondo Beach, California > _______________________________________________ > 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.