On Mon, 5 Dec 2005, fred jones wrote:

>
> There are a lot of smart minds here so I thought I'd check with you all.  I 
> am interested in building a magnetometer.  I know that manufacturers commonly 
> use Gel Cell batteries because they are non-ferrous and won't interfere with 
> the mag.  With the power capacity to weight efficiency gain with using a Nimh 
> battery pack, I'm trying to find out if they are ferrous or not.  Are there 
> any battery experts here that know the answer?
> Thanks,

Nickel is magnetic but has no remanence. In theory you should be ok if 
the batteries are very far away from the detector. 2 meters or so shoudl 
do it.

Fyi the terminals of most discrete parts and ICs are ferrous and will 
have a remanent field after being exposed to magnets (like the Earth) 
for a while. If you care about this then you can degauss the circuit 
(with care). If not, just mount it far from the sensor with the 
batteries.

Peter
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