[volt-nuts] Traveling Standards

[Fred Schneider]

So I have nothing to complain, after the first week changing " much" it now goes up/ down a bit with temp and probably humidity. At 10V, 1ppm is 10 uV so it is changes 5 to 6 ppm over 5 degrees. Today it changed less then 1 ppm over 3 degrees so I that leaves humidity. I do not have a hygrometer so it becomes time I get one.

Thanks for the tips for the common mode, i will try it soon,
http://www.pa4tim.nl/wp-content/uploads/2011/06/lm399schema_1.jpg
This is the schematic ( completely my own design but I'm no EE so it probably will not be to great) but I appriciate comments for improvement.
http://www.pa4tim.nl/?p=2531 pictures are at the bottom of the page, all my reference experiments are here together. 

Fred PA4TIM

Op 20 okt. 2012 om 17:41 heeft "Andreas Jahn" <Andreas_-_Jahn at t-online.de> het volgende geschreven:

> 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
> 
> 
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