HI
On Mar 2, 2014, at 4:00 PM, Magnus Danielson <mag...@rubidium.dyndns.org> wrote: > On 02/03/14 21:45, Bob Camp wrote: >> Hi >> >> The gotcha is that there are second order temperature effects. If you are >> going to run the crystal very far off turn, you need to keep it more stable >> than you might think. > > "hysteresis", "memory effect", "restart of frequency drift” In addition to those there is actually a “temperature rate of change” dependent frequency change coefficient. It varies with the angle of cut and the temperature. > > Yeah, it puts a limit on how good a TCXO can track-and-compensate. > > I was also considering the use of XOs for temperature sensing, it has the > benefit that it is relatively easy to sense with resolution, but after that > frequency/phase measures is in, getting a good temperature reading isn't as > easy. > > Is there a good temperature-sensing set of modes in AT-cut crystals, as I > know being used in SC-cut crystals? As Jim mentions in another post, you can run on the fundamental and the third (or 5th or 7th) and get a thermometer out of the delta between the two modes. The gotcha is that a change in load impedance will shift the frequencies unequally. That will give you an apparent temperature change. Bob > > Cheers, > Magnus > > _______________________________________________ > 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.
