[time-nuts] Cheap Rubidium

[Bob Camp]

Hi

I may be looking in the wrong places for my parts. The ones I have seen appear to use about a watt to pump a watt at zero delta T. That still means putting a lot of DC current into the system. 

I'm thinking that a recirculating water loop with a radiator (or TE cooler) remote from the rubidium may be a reasonable way to go. I still need to do some homework on cost. 

Bob

 
On Dec 24, 2009, at 11:54 AM, J. Forster wrote:

> 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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> 
> 
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