Hi There’s no particular reason to stop at the 100:1 point. You can run multiple loops at the same time and get out to essentially any level of precision. The only question is over what averaging interval the precision applies. In some cases this elastic definition does just fine.
Bob > On Nov 2, 2017, at 3:32 PM, Tom Van Baak <t...@leapsecond.com> wrote: > >>> The DS3231 has an 8 bit register that will change its frequency in >>> increments of about 0.1ppm. Thus you could discipline it to get its pps >>> aligned with your reference. >> >> That sounds like you just designed the worst GPSDO ever. > > You could argue that the worst GPSDO ever is an operating system running NTP > ;-) A PC running NTP at +/- 10 us is a thousand times worse in time accuracy > and a million times worse in frequency stability than a TBolt GPSDO. > > But back to the DS3231. If the 0.1 ppm increment sounds too coarse to you, > then just step between N-1 / N / N+1, similar to how PWM works. Don't laugh. > Some microcontrollers also have programmable oscillator tuning and I tested > this on a PIC -- microstepping 100 times a second -- as part of my "best > worst GPSDO" project. > > http://leapsecond.com/pic/src/pg41.asm > > /tvb > > _______________________________________________ > 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.