[time-nuts] Temperature measurement crystals

Murray Greenman murray at rakon.co.nz
Sun Dec 9 13:12:56 EST 2007


Y-cut crystals are commonly used for temperature measurement.

One typical application is to mount a Y-cut and an AT-cut device in the
same housing with two identical oscillators, and use one to predict
(with limitations) the frequency of the other over temperature.

You can also use two oscillation modes in the one crystal, for example
fundamental and 3rd overtone in AT cut, or B-mode in SC-cut. Much more
complex to achieve desired results in practice though!

The limitation to this type of technique is that while the static
performance of Y-cut temperature sensors (and AT-cut too) is reasonable,
the response to temperature velocity differs with the cut or oscillation
mode, and so presents a limit to how well one can be used to predict or
compensate the other. Some applications, such as fast time-to-first-fix
GPS or indoor GPS, require better than average short-term stability,
achievable only with excellent temperature velocity performance.

Murray Zl1BPU



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