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Re: E-field Applications?



At 09:06 PM 4/8/97 -0400, Tony Wayne wrote:

I just read an article from theis past Sunday's newspaper about a company
that markets an electric shark repellant. the device has an eletrode that
attaches to a divers air tank and another electrode to his swim fin. when
energized be a 12 volt gel cell the 2 electrodes emit a e-field "bubble"
around the diver that repels sharks at close range and lasts for 90 minutes
before the cells need recharging. A cool application of an e-field.
Do you know of any other applications/devices that use an e-field?
-tony


It was a while ago I had an interest in animals' navigation abilities.
I read an interesting paper on measuring sharks' electric field sensitivity.
I went to see the person who had done this work ( where I heard of the
difficulties of getting tenure at Woods Hole)

Come to think of it, I also visited some people at Stanford,
who had produced some evocative results using simple electrodes driven
into a live tree trunk, which turned out to be due to low frequency radiation
from the BART -Bay Area Transit System - whose nearest line ran several
miles away. The sensing effect was abolished when the tree died.

Sharks have an acute sensitivity to minute electric fields.
It was thought that this provided guidance towards prey.
Their field sensor is located in the snout.
I suspect that a large field of the kind described could indeed be offputting.

To provide a generalized answer to the practical use of e fields,
you may be familiar with cathodic protection of pipes and boat hulls.
There is some interesting work on "pumping" water away from house
foundations with an efield. Straying farther afield, mapping earth resistivity
for mineral exploration comes to mind.

Regards
brian whatcott <inet@intellisys.net>
Altus OK