[time-nuts] Cheap Rubidium

[J. Forster]

The trick is you use the TE devices at near zero delta-T. They will pump
much more heat and dissipate little power.

-John

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


> 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>:
>>> At 10:06 PM +0000 12/23/09, time-nuts-request at febo.com wrote:
>>>>
>>>> Date: Thu, 24 Dec 2009 09:46:13 +1300
>>>> From: Bruce Griffiths <bruce.griffiths at xtra.co.nz>
>>>> Subject: Re: [time-nuts] Cheap Rubidium
>>>> To: Discussion of precise time and frequency measurement
>>>>        <time-nuts at febo.com>
>>>>
>>>> Joe Gwinn wrote:
>>>>>>
>>>>>>  Date: Thu, 24 Dec 2009 08:57:42 +1300
>>>>>>  From: Bruce Griffiths <bruce.griffiths at xtra.co.nz>
>>>>>>  Subject: Re: [time-nuts] Cheap Rubidium
>>>>>>  To: Discussion of precise time and frequency measurement
>>>>
>>>>  >> <time-nuts at febo.com>
>>>>>>
>>>
>>> [snip]
>>>
>>>>>  >> Distributed heating using wire wound or printed heaters perhaps,
>>>>> but
>>>>> to
>>>>>>>
>>>>>>>  reduce the associated magnetic field bifilar winding should be
>>>>>>>  considered.
>>>>>>
>>>>>>  Non-inductive power resistors, which are commercially available,
>>>>>> have
>>>>>>  very low magnetic fields.
>>>>>>
>>>>>>  The low-inductance resistors have Ayrton-Perry windings, which are
>>>>>>  bifilar.
>>>>
>>>> No, Ayrton-Perry windings arent bifilar.
>>>>
>>>> Classically a flattened helical winding was made on a insulating card.
>>>> An identical winding was then wound in the opposite direction on top
>>>> of
>>>> the first winding and the 2 were connected in parallel.
>>>> The idea being that the small magnetic field produced by one flattened
>>>> helix is cancelled by that of the other flattened helix.
>>>
>>> True enough - while there are two conductors, they are not close and
>>> parallel.
>>>
>>> Anyway, the point is that non-inductive components by definition have
>>> low
>>> magnetic fields, and that non-inductive power resistors are common.
>>>
>>> To eliminate the field from the loop of resistors, one can have a
>>> linear
>>> string of A-P resistors in series, with a pair of return wires in
>>> parallel,
>>> with the return wires on either side of the resistor string, thus
>>> reducing
>>> the effective loop area.
>>>
>>> Joe
>>>
>>>
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>>
>>
>>
>> --
>> Steve Rooke - ZL3TUV & G8KVD
>> A man with one clock knows what time it is;
>> A man with two clocks is never quite sure.
>>
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>
>
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