[time-nuts] Temperature controlled TCVCXO

[David]

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.