[volt-nuts] HP3450A Reference Peltier Chambers
phk at phk.freebsd.dk
Fri Nov 27 14:12:35 EST 2015
In message <F57B1617EE984B10AAD5379A2402DFE6 at D77M7BF1>, "Dave M" writes:
>I was intrigued by the use of a Peltier chamber to control
>the temperature [...]
It's a very obvious idea, but it runs into one of the widely unknown
footnotes about peltiers: Don't feed them AC.
The thermal/mechanical stress when you change direction of the
current significantly shortens their life.
I should add that I have not found any studies which say to what
degree this depends on the magnitude of the current, so an oven
balancing around a couple of mA may not be a problem, but switching
polarity on several amps will be.
One complication is the difference in directional efficiency: The
warm side receives about 4 times as much energy as is removed from
the cold side.
Unless you electrically compensate for this, your PID will be
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