On Fri, 13 May 2016 11:38:06 -0500, you wrote: >David wrote: >> I was thinking of holding the temperature right at 25C or maybe a >> little higher at an inflection point to minimize the possibility of >> condensation. The difficulty is that the ambient temperature could >> vary above or below that so the TEC has to both heat and cool but that >> is a solved problem. > >The HP 3450A & B model digital multimeters used a Peltier device to control >the temperature of the voltage reference zener diode. You can download the >manual for the "B" model from Keysight's web site to get an idea of the >control circuitry >(http://www.keysight.com/main/techSupport.jspx?searchT=3450B&id=3450B:epsg:pro&pid=3450B:epsg:pro&cc=US&lc=eng). > >There's also a sales bulletin for that model that gives a bit more >information about the Peltier device and chamber >(http://www.ko4bb.com/getsimple/index.php?id=manuals). Search for 3450A on >that site. > >The chamber is controlled to 43C by the Peltier device, allowing quite fast >warmup times for the instrument, and operation above normal environmental >temperatures. > >Cheers, >Dave M
It figures that HP would have done this if anybody had. I am not that familiar with their design history so thanks for bringing this to my attention. I did not find anything in the theory section of the original service manual although it does have the schematic but K04BB has a supplement which discusses the 3450A peltier chamber and circuit in detail. They even sort of mention that the gain of the peltier differs significantly between heating and cooling. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
