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Gabriel, David
12-20-1998, 11:27 PM
Dear Colleagues:

My great appreciation to those who responded. Perhaps due to the time of
year, there were not many responses. Nevertheless, science moves on. I
have cut and past the responses below.

Once again, thank you to the respondents

David A. Gabriel



Dear David,
I looked into building a Faraday cage 10 years ago, and if I remember
the cost was about $5000. You'll find that locating a source for
copper screening will be very difficult and a reasonable width will
be problematic. The screening should also cover the floor. You may be
able to find an electrically shielded environmental chamber.
Good Luck,
Al Finch
Biomechanics Lab
Indiana State University

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Some years ago, I was involved in an EEG study, and a small shielded
room was constructed with soft aluminum sheet, such as is used as stock
for soft drink cans. This material was picked up as aluminum scrap at a
can plant where one of our group was working. The real expenses of such
rooms are in the door, any needed windows, and in arranging the signal
paths so that the shield integrity is not violated by the signal
handling wires. In general, this requires either batteries inside the
room (which we used) or multiply shielded isolated power supplies, as
well as isolated instrumentation amplifiers to get the signals out
through the shield. At a minimum, a single shield which is connected at
a single point to the common low side of the amplifier inputs, and with
scrupulous care to insure that no current is drawn _through _ the
shield. Ralph Morrison has written a book on _Shields and Grounds_,
published recently, which I am sure covers the matter in great detail,
judging from what I know of his 1964 book on the topic. Many users of
shielded rooms put one shield inside another, and this allows
considerably more flexibility in connection of grounds, as well as
somewhat less stringent requirements of "tightness" of each shield. In
short, getting power and signals in and out of the cage turns out to be
much more of a problem than putting up a shield. Bob

__________________________________________________ __________


Dear Gabriel,

Our neuro reserachers used to conduct microvolt trans-membrane cell
potential studies down the hall from me using a home-made cage that looked
alot like my sister's screened porch. The frame was made of aluminum "ell"
stock, and the screen was directly from the hardware store. I imaging
copper might be better for high frequency, but this one worked very well....
and it was a very noisy environment(electrically, that is).

I kindof recall there being a book, or book chapter on building inexpensive
faraday cages, but I cannot remember where.

Best of luck.

JFA

James F. Antaki
Director, Artificial Heart Research
McGowan Center for Artificial Organ Development
University of Pittsburgh
Pittsburgh, PA 15219
antakiJF@msx.upmc.edu
__________________________________________________ ____

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