[volt-nuts] Traveling Standards - pictures

[Andreas Jahn]

>
> I'm not sure what caused the shift around 09-20.
>
Was the reference powered all the time? And your meter too? What tempco has 
your meter?
Did you change orientation of the reference (20-30uV is the change that I 
have with orientation).
But perhaps you have simply a bad device like my LM399#1

Attached you will find the drift of my References LM399#1 LM399#2 LTZ1000#1 
LTZ1000#2
measured as average with two 24Bit ADCs ADC4 + ADC8 (with a LT1027CCN8-5 
reference each).
The drift of LM399#2 LTZ1000#1 LTZ1000#2 is mainly equal. -> that what you 
see is mainly the
drift of the plastic references (LT1027) of the ADCs caused by relative 
humidity.
(Tempco of the LT1027 is calculated out/compensated during measurement).
Solely the LM399#1 drifts uncorrelated -> something is wrong with this guy.

By the way: it would be better for resolution to measure several devices as 
absolute and difference values.

with best regards

Andreas
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Ref_drift.PNG
Type: image/png
Size: 41557 bytes
Desc: not available
URL: <http://www.febo.com/pipermail/volt-nuts/attachments/20110926/761e30a8/attachment-0001.png>