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From: hogstedt@ae.chalmers.se (PER HOGSTEDT)
Newsgroups: sci.electronics
Subject: What is the noise voltage of a 1.5V cell
Message-ID: <1991Jan3.001303.483@ae.chalmers.se>
Date: 2 Jan 91 23:13:02 GMT
Organization: Dept. of Applied Electronics. Chalmers Univ. of Technology.
Lines: 26

I need to produce a voltage that is going to be used to bias
a high sensitivity magnetometer (intrinsic noise < 1 pT/sqrt(Hz)) exposed
to the earth's magnetic field. The long term stability demands on this
voltage source are moderate, but the voltage noise has to be extremly low.

I have tried some "reference voltage" IC:s and they are indeed very stable,
but the noise level is too high. The noise level would have to be below
what corresponds to <1/2LSB of a 22 bit A/D converter to utilize this beast
to it's full. Can you send me a dozen :-)

As a kind of last resort, I would like to know what the noise is of a 
regular 1.5V (e.g. alkaline) cell, assuming the cell is kept at
room temperature and loaded only by some microAmps?

Yes, if you have that super duper low noise circuitry I'm looking for at hand
I'm certainly interested in any pointers. 

The bandwidth of primary interest is DC to maximum 50 Hz.

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   Per Hogstedt               Internet:  hogstedt@ae.chalmers.se
   Lindholmen R&D                   or:  hogstedt@plab.se
   P.O. Box 8714              Phone...:  +46 3 50 70 50
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