[volt-nuts] Tilt effect on Keithley 2000

Andreas Jahn Andreas_-_Jahn at t-online.de
Mon Sep 6 05:00:23 UTC 2010

Marvin wrote

> Joe Geller suggests the current draw of the LM399 heater is sensitive 
> to very small changes in ambient temperature, he exploits this in his 
> microgust anemometer circuit.  When orienting an exposed chip, very 
> small temperature gradients exists between open air and a table, 
> particularly with fan or window making small air currents.
thanks for your contribution. 
In my LM399 references I wanted to have a minimum power 
consupmtion when using battery supply.
So I did not remove the foam cup of the device.
Instead I packaged the small PCB with the LM399 and the
temperature compensated current source into a housing of 
polystyrene foam. This housing is packaged into a card box.
So there should not be much air current inside.
The most confusing fact is that the power consumption
is a minimum when turning the LM399s up side down
with the pins in upper direction. The foam cup has a 
relative large hole for all 4 pins.

best regards


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