[time-nuts] Cheap Rubidium... more

[J. Forster]

Let me expand a bit:


OSC ==== TE ==== Heat Sink
@T1                @T2

If you configured the system this way and applied NO power to the TE
device and T1 > T2, heat would STILL flow from the Oscillator to the Heat
Sink. The TE will just have a thermal resistance like a block of aluminum
or cheese. (this assumes REASONABLE temperatures, below the melting point
of the solder in the TE device)

Now, if the Osc is too hot, you apply some power to the TE device to
increase the heat transfer to the HS. If too cold, do the opposite. If the
Osc temperature is just right, don't power the TE at all.

Note: With TE refrigerators, the fact that the TE element conducts heat
even when switched off is a serious fault. Here it helps.

-John

================

Exactly.

You use the TE device as a fine control element. The fact that it is
thermally bipolar makes loop design a whole lot easier. It is also FAST,
unlike fans and circulating water.

-John

================


>>The problem with cooler chips is ...
>
> The Real Problem seems to be some don't have much practical sense. A
peltier would work GREAT, (along with many other simple active ways).
You don't need to make a refrigerator with it.
> You just need to just keep the temperature of what it is attached constant.
> One way to do that, is to mount one side of a  peltier to a working
unit's heat sink
> AND Adjust everything so that the nominal power into the peltier  is
near ZERO.
> Now it can cool or heat the THING it is attached to just a little to
make up for the room temp variation.
>
> Then some simple person may ask why bother with the cooling side at all,
why not make it unipolar and just use the heat side,
> by using a little larger heat sink on the thing or running the nominal
Temperature a little higher?
>
> ws
>
> *********************
>
> Hi
>
> THe problem with cooler chips is that the heat still has to go
somewhere. On the "other side" of the device you need to deal with both
the original 10 or 20 watts plus the heat from the cooler. To move 10 or
20 watts and get a significant delta T you need a pretty big cooler
chip. Since they are low voltage, that gets you right back to lots of
current and thus magnetic fields.
>
> The idea of putting the cooler a distance from the cell and coupling
with moving air is still an option though.
>
> Bob
>
>
> On Dec 24, 2009, at 9:28 AM, Steve Rooke wrote:
>
>> I wonder how peltier devices would work for this application. Coupled
with a temperature feedback servo they could be used to heat/cool the
rubidium. Does anyone know if they have any electromagnetic field
issues with them, the ones I have seen seem to be completely enclosed
in aluminium which should act as a Faraday cage. They have the
>> potential of providing a large thermal transfer capability compared
with passive devices.
>>
>> 73,
>> Steve
>>
>> 2009/12/25 Joe Gwinn <joegwinn at comcast.net>:
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