[time-nuts] Temperature controlled TCVCXO

[Bill Hawkins]

Note that the 3450B has an accuracy of 10E-5.

You're probably looking for something a lot better than that.

Bill Hawkins 

-----Original Message-----
From: David
Sent: Friday, May 13, 2016 8:28 PM

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:e
psg: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.