Hi Poul,
By replying to my reply to Leigh, and clipping out everything
that I wrote (but my name), you seem to be attributing to me,
what Leigh wrote.
You then rephrased my statement about heaters in the physics
package, restated my statement about extra cooling increasing
the power drawn by the heaters.
You then clarified things greatly by advising to not run the Rb
too hot, but also don't cool it too much.
???
If you have so much to say to the original author, and nothing to
say about my reply, wouldn't it have been be better to just reply
to his message, instead of mine?
-Chuck Harris
Poul-Henning Kamp wrote:
In message <[email protected]>, Chuck Harris writes:
I ran the device today for about half an hour, and used an infrared
sensing thermometer to measure the external case temperature.
Be very careful about trusting this: you need to do some tricky
calibrations to get anywhere near precise when you measure metal
surfaces.
The easy way, is to put a piece of duc[kt]tape on the metal surface
and make sure your thermometer can see only that surface.
Unfortunately, the tape will also act as insulation, so the result
you get is not precise even then.
It got up to 48 C externally in the physics package area.
That's quite normal.
Those small Rb's keep the internal temperature constant using
heaters, which can raise the temperature and by being able to dump
excess heat through their heat-sink to lower the temperature.
You shouldn't run your Rb too hot, as this decreases the electronics
lifetime and reduces the wiggle-room of the thermal management
inside the device.
On the other hand, cooling it too much will only increase the
power drain for the heaters and increase the thermal gradients
inside the unit, likely degrading thermal stability.
Poul-Henning
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