[time-nuts] poor-man's oven

[jimlux]

On 6/4/17 10:01 PM, Chris Albertson wrote:
> Voltage is proportional to the product of resistance and absolute
> temperature.   As an experiment place a voltage across a high value
> resister like say one 1M  raise the volts until you are near the limit of
> the resister and connect it via a coupler cadaster to an audio amplifier.
> You will hear white noise in the speakers.

As in Johnson noise - vrms = sqrt(4kTR)

>
> There is a similar effect in semi conductors.  The best example of this is
> visual noise in digital camera, when you tern the gain way up (set the ISO
> high) you can see it in the photo.

I believe that's a different mechanism, shot noise.

>
> All of this is proportion; to absolute.
>
> As I remember we ran the "oven" at -20C There was a valve used to flash out
> the air inside with inert welding gas to reduce ice.
>
> Some people use vacuum and get to cryogenic temperatures.  But that is
> expensive and way-hard without an institutional size budget.
>
>

cryogenic (as in LN2 temps) is very hard with TEC it takes many stacked 
devices that wind up looking like a ziggurat.

near vacuum isn't that tough at home - refrigeration vacuum pumps are 
inexpensive.  If it's a one time thing, a sorption pump and one time Ln2 
or Dry Ice can get you pretty empty as a one shot. Then you seal it off 
and it's done.
the Bell Jar - http://www.belljar.net/  is a handy reference of vacuum 
hacking stuff


>
>
>
>> What is the reason why you'd expect less noise with a TEC?
>>
>>                         Attila Kinali
>>
>> --
>> You know, the very powerful and the very stupid have one thing in common.
>> They don't alters their views to fit the facts, they alter the facts to
>> fit the views, which can be uncomfortable if you happen to be one of the
>> facts that needs altering.  -- The Doctor
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