nuckollsr(at)cox.net Guest
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Posted: Sun Nov 26, 2006 6:18 pm Post subject: Foil Shielding |
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Quote: | Can you suggest a good way to ground shielded wires that use foil for
shielding? I like your method for the braided wire, can find no reference
for foil shielding. Thanks.
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As you've observed, wires may be "shielded" by a variety
of techniques. The earliest shielding was accomplished with
an over-braid of fine wires. Obviously, braided wires cannot
offer 100% coverage for shielding effectiveness. Know that for
the vast majority of things we do in airplanes requiring
shielded conductors, one layer of tightly overbraided wires
will achieve 80% or better coverage and is just fine.
I think back in 60' or early 70's, Belden Wire and cable
figured out a simpler way to increase shielding coverage
and simplify construction by using thin aluminum foil to
instead of overbraid. One problem was that the aluminum
foil was a muther-bear to make connections so a "drain wire"
was added to the stranding makeup of the cable. The drain wire
may be inside or outside the foil and is always uninsulated
so that it makes contact with the foil over length of the cable.
See a couple of documents on my website at:
http://www.aeroelectric.com/Mfgr_Data/Wire/Belden
The short answer to your question is, "Don't try to
mess with the aluminum foil as a conductor. Find the
Drain Wire and use it to achieve connection to the
foil."
Bob . . .
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< What is so wonderful about scientific truth...is that >
< the authority which determines whether there can be >
< debate or not does not reside in some fraternity of >
< scientists; nor is it divine. The authority rests >
< with experiment. >
< --Lawrence M. Krauss >
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