[volt-nuts] Tilt effect on Keithley 2000

Andreas Jahn Andreas_-_Jahn at t-online.de
Sun Sep 5 07:21:14 UTC 2010

Charles wrote:

>What is the time constant?  Slowish (i.e., could be thermal) or rapid 
>(presumably gravitational/mechanical stress)?

The 20-30uV on my LM399s should be thermal. Time constant
is about 10 seconds. Additionally the current consumption of 
the reference cirquit changes by 3-5%. So I think that the
heater within LM399 has not a good thermal layout with respect
to the temperature sensor on the same chip.

For the Keithley differences I cannot tell the real time constant 
since I had slow reading with averaging 10 or 50 measurements.
But since the effect is significantly larger than the reference alone
there might be a mixture of mechanical and thermal effects.

best regards


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