Yes, I'm aware of the problems with AC drive to a Peltier. However, the 3450A drives the chamber to 43 degC with DC, so that isn't a problem. In fact, it's a pretty simple drive circuit, runing stable state at 1.5 - 2 volts.
My interest is in how best to fix the components to the Peltier. Seeing a picture of the innards of the 3450A chamber would help. I have a few 12V Peltier junctions of various powers ratings, and have no other thoughts as to what to use them for. Making a small chamber to ascertain the zero tempco point of my reference zeners seems to be an easy project. This isn't for a constantly-on instrument; it's for short-term data gathering. Thanks, Dave M Poul-Henning Kamp wrote: > -------- > In message <F57B1617EE984B10AAD5379A2402DFE6@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 > *really* confused. _______________________________________________ volt-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
