[volt-nuts] Tilt effect on Keithley 2000
Charles P. Steinmetz
charles_steinmetz at lavabit.com
Sun Sep 5 03:54:34 UTC 2010
>I am playing around with some reference voltages and found out that my LM399
>references have 20-30 uV change in output voltage depending on the
>orientation of the reference.
>So when calibrating my voltage references with a Keithley 2000
>I found out that the reading changes on the Keithley too
>depending of the orientation of the instrument.
What is the time constant? Slowish (i.e., could be thermal) or rapid
(presumably gravitational/mechanical stress)?
I have operated Fluke 732As and 5440Bs in various orientations and
have not noticed any changes. With the 732s I was specifically
looking for changes with orientation, and didn't see any to the limit
of my methods (around 0.1 ppm). With the 5440B I wasn't specifically
looking for an orientation effect, but I think I'd certainly have
noticed 1 ppm. Of course, neither instrument uses an LM399 or LTZ1000.
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