[volt-nuts] Traveling Standards

[Andreas Jahn]

Hello Fred,

> It is now 24/7 on for about 5 weeks.

5 weeks is nothing in the life of a reference.
During the first year my 2 LM399 references drifted 500uV against each other

The 2nd year it was only 220uV
now I know that LM399 #1 is drifting much more (200uV) than LM399 #2 (20uV) 
in the 2nd year.

In the 3rd year LM399#1 drifted around 140uV and LM399#3 less than 10uV.

So not all references seem to be usable for precision measurement.
Its shurely no fault to start with a set of several references and select 
out the bad ones.

With best regards

Andreas