If your DAC spans the full EFC range than 1LSB is 1/2^20 ~ 1 PPM of the EFC range, and the EFC tuning range is 8/10E6 ~ 1 PPM full scale, so 1 LSB is ~1PPT. So, if everything else is stable the DAC code reflects changes solely due to the OCXO, which would be an aging of 24 PPT/day.
On Sat, Nov 5, 2016 at 9:57 PM, Bob Stewart <[email protected]> wrote: > Hi Scott, > > The 20 bits span about 6 volts. The EFC range spans about 8Hz (+/-4Hz). > I don't do these calculations every day, but that's about 4.5PPT? > > Bob > > ----------------------------------------------------------------- > AE6RV.com > > GFS GPSDO list: > groups.yahoo.com/neo/groups/GFS-GPSDOs/info > > > > > ------------------------------ > *From:* Scott Stobbe <[email protected]> > *To:* Bob Stewart <[email protected]>; Discussion of precise time and > frequency measurement <[email protected]> > *Sent:* Saturday, November 5, 2016 8:38 PM > *Subject:* Re: [time-nuts] Thermal impact on OCXO > > I think that's a nice plot, it looks like you have stepped 160 LSB over 7 > days or roughly 1 LSB per hour. With a 20bit dac you are trimming maybe 1 > ppt/LSB to 4 ppt/LSB? In allan devation terms, the case of 1ppt/LSB, solely > due to drift, you're at 1E-12 at 3600*sqrt(2) = 5000 s, in the case of > 4ppt/hour your at 1E-12 at 1280 s. Seems reasonable. > > On Sat, Nov 5, 2016 at 2:47 PM, Bob Stewart <[email protected]> wrote: > > Oh dear. I attached the wrong file. Here's the correct one. > ----------------------------- ------------------------------ ------ > AE6RV.com > > GFS GPSDO list: > groups.yahoo.com/neo/groups/ GFS-GPSDOs/info > <http://groups.yahoo.com/neo/groups/GFS-GPSDOs/info?soc_src=mail&soc_trk=ma> > > > > > ______________________________ _________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > <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.
