[time-nuts] Frequency referenced temperature regulator
Charles P. Steinmetz
charles_steinmetz at lavabit.com
Mon Nov 8 15:36:44 UTC 2010
Poul-Henning Kamp wrote:
> But since I happen to have access to much more stable frequencies
> than voltages, I thought of a different way:
>
> 1. Mount a X-tal-osc with really lousy tempco inside the enclosure.
>
> 2. Compare its output to a stable reference frequency.
>
> 3. Use the output of the phase comparator to drive the Peltier.
>
> It is basically a PLL where temperature is used as EFC...
>
> Has anybody tried that ?
Frequency comparison between two oscillators, one a low-tempco and
the other a high-tempco, is used by Dallas in the new version of the
infamous (to Time Nuts) DS1620 temperature sensor. See the current
datasheet and Dallas AN-105. I assume neither is an XO, nor do they
phase lock them. Instead, they count the higher-frequency,
low-tempco oscillator using the lower-frequency, high-tempco
oscillator as a time base, then correct for nonlinearities.
Best regards,
Charles
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