Hi That paper is the basis for the MCXO. It is an interesting way to do a TCXO. The drift between the two modes makes it a difficult thing to master in an OCXO. Plating a pair of electrodes (one pair per mode) is also an approach that has been tried.
Bob > On Jun 5, 2017, at 7:20 PM, Chris Caudle <ch...@chriscaudle.org> wrote: > > On Mon, June 5, 2017 5:38 pm, Charles Steinmetz wrote: >> Some years ago, I consulted for a research group that was using a number >> of non-contact technologies to measure the temperature of oscillating >> quartz crystals. > > In most cases what you really care about is the stability of the > frequency, and the temperature of the crystal is just a proxy for that, > correct? > I thought there was some effect where different modes of oscillation > shifted by different amounts with temperature, and if you had two > oscillation circuits running from the same crystal but different modes, > you could use the shift in difference frequency between the two modes to > infer the temperature change. > > Found a reference in the Vig tutorial: > S. Schodowski, "Resonator Self-Temperature-Sensing Using a > Dual-Harmonic-Mode Crystal Oscillator," Proc. 43rd Annual Symposium on > Frequency Control, pp. 2-7, 1989, IEEE Catalog No. 89CH2690-6. > > From page 48 of Vig tutorial version 8.5.5.3 May 2013: > As is shown in chapter 4, see Effects of Harmonics on f vs. T, the f > vs. T of the fundamental mode of a resonator is different from that of > the third and higher overtones. This fact is exploited for > self-temperature sensing in the microcomputer compensated crystal > oscillator (MCXO). The fundamental (f1) and third overtone (f3) > frequencies are excited simultaneously (dual mode excitation) and a > beat frequency fb is generated such that fb = 3f1 - f3 (or fb = f1 - > f3/3). The fb is a monotonic and nearly linear function of > temperature, as is shown above for a 10 MHz 3rd overtone (3.3. MHz > fundamental mode) SC-cut resonator. > > The graph shows a line with slope of around 80ppm/deg C. Not sure what > that translates to in terms of what you could realistically measure and > use for frequency compensation. I guess you could use that information to > either control an oven or just let the crystal run free and control a > synthesizer for the used output. > > -- > Chris Caudle > > > > > _______________________________________________ > 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.