[time-nuts] Airflow around oscillators.

Poul-Henning Kamp phk at phk.freebsd.dk
Sun May 22 13:24:24 EDT 2005

In message <004601c55ef0$ebc14100$0500a8c0 at darius.domain.actdsltmp>, "Bill Hawk
ins" writes:

>If you put thermal insulation around the oscillators then the fan
>will be of little use. Poul-Henning Kamp's suggestion of a 
>relatively large insulated box with some internal air circulation
>is excellent. 
>Now, if you could mathematically model
>the effect of ambient temperature, you could measure ambient and
>pass it through the time-dependent model to become feed-forward
>for the oscillator ovens. You'd have to rebuild the oven controllers.

For the old fridge model there is a much easier way:  Run water of
constant temperature through the in-side loop and control the temperature
of the water actively in both directions.

I heard about this setup from some professional metrology people who
have managed milli-kelvin stability that way.

They also advocate putting one of the small "pin-hole" CCD cameras in
there so you don't have to open the door to see that nothing has fallen

Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.

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