On Mon, 6 Dec 2004, Eric Smith wrote:

> Paul wrote:
>> transfer my pid control into my solding iron and found
>> such a good try.  With my solding iron been pid controlled, the
>> temperature goes within 3 degree and give such perfect, small sodling.
>> It is much better perforomance than expensive Weller products (it gives
>> 20C deg moving normally). By the better controlling, I now can set my iron
>> at 197 C and get all kind of benefit with this temperature.
>
> I don't know, but perhaps PID control is used in Metcal soldering
> equipment.  They certainly seem to have much better temperature
> regulation than anything else I've used.

Afaik they use the same Curie effect as Weller/Cooper do, but unlike 
Weller the sensor *and* the heater is the bit itself. This means that 
temperature regulation depends on the Curie point (very sharply defined) 
at a very small distance from the work (fractions of a millimeter 
probably). F.ex. it should be possible for the left half of a 0.8mm bit to 
be colder by 0.1 degrees C than the right and it to receive power from the 
rf heater source, while the other half doesn't.

Peter
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