[time-nuts] Hobbyist grade or homebrew temperature testing chamber?

Neville Michie namichie at gmail.com
Tue Sep 6 01:55:32 EDT 2016


Constant temperature chambers are not hard to build.
I assume you want stability in the range 0.001 to 0.01 degC.
I have made a few of these chambers, about 1 cubic feet, out of 3/4 inch particle board,
it is not a brilliant insulator, but you want some heat loss.
Make a partition at one end with both ends open as a radiation wall.
Behind the radiation wall instal one or two tungsten filament lamps,
about 50 watts for heaters, these have low thermal mass and fast response.
Instal a computer sized fan, behind the wall to reduce any radiant output to circulate the air in the box.
You want a small hurricane. On the far side of the box from the partition place a small bead thermistor, 
glass encapsulated are good. In the air flow this should have a response time of a second.
A proportional controller sets the temperature. Air velocity of up to 1m/s will not disturb items being tested 
but ensures low temperature gradients.
The trick is to have fast response in heater and measurement and no hysteresis in the controller.

cheers,
Neville Michie




> On 6 Sep 2016, at 12:48 PM, Richard (Rick) Karlquist <richard at karlquist.com> wrote:
> 
> As we all know, step #1 in making a clock is NOT
> to build a thermometer :-)
> 
> I thought I would check the brain trust here to see
> if anyone has seen a hobbyist grade temperature
> testing chamber or kit or homebrew design.  I
> have some crystals, oscillators, and other
> electronics I would like to characterize over
> temperature.  I know this reflector has discussed
> homebrew stabilization ovens; however, they
> have tended to have very long time constants
> (which makes sense for that application).  I
> need to be able to change temperature in a
> reasonable amount of time, and I don't need
> extreme stability.  Looking for any ideas,
> maybe in the "maker" spirit.  I think the
> size I need would be perhaps 1/2 the size
> of a shoebox.
> 
> BTW, in case someone has a chamber to sell,
> let me know...
> 
> Rick Karlquist N6RK
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