[volt-nuts] Traveling Standards

[Charles P. Steinmetz]

Demian wrote:

>To make a real PPM standard has so many technique pitfalls that it may be a
>really frustrating experience.  *   *   *
>If you look at the manuals and construction efforts for these things there
>is a lot of experience in details that's hard to just copy. Even the circuit
>layouts and managing the thermocouples in all the connections is not
>trivial. Here is a good starting point for understanding it:
>http://cds.linear.com/docs/Application%20Note/an74f.pdf

Linear Technology's Application Notes AN42, AN82, AN86, and AN124 
also contain valuable information on the topic.  The Linear 
Technology Design Note DN229 discusses reference hysteresis, 
including the thermal shock from soldering.

>I also have a 732A, a Prema DVM and a Fluke 8506a, all of which use 
>LTZ1000 references.

I believe the 732A uses a common-substrate zener + transistor in an 
oven assembly that contains the whole reference circuit.

Best regards,

Charles