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"Beldfoil" specs

Can someone familliar with Beldens "Beldfoil" aluminium-polyester screening foil please tell me how it is constructed?

It is typically used with a drain wire in their shielded cables.

What I need to know is if a voltage is applied to the drain wire, is it conducted throughout the entire surface area of the Beldfoil screen?

To rephrase, is the film continuously conductive? Or does it have discontinuities (laps, etc.) spanned by the drain wire?

Am I correct in assuming the poly part faces inward toward the signal wires?

The point is, I want the entire screen to carry the current, not just the drain. I realize it's not normally used this way, but it is an experiment.

Thank you for any advice.

Tim Lamer

Reply to
Tim Lamer
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As Belden makes it, the aluminized, conductive surface is on the inside and the drain wire is in intimate contact. At least that is the way it was made 30+ years ago when Belden came out with the scheme...

Reply to
Robert Baer 

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http://www.belden.com/pdfs/Cable101/Shielding.pdf
Reply to
John Fields

It's not Belden, but I have a roll of Alpha 2403C (Mouser.com part #

602-2403C-100), which has three 22AWG conductors, plus foil shield and drain wire. In this case, the silver conductive part of the shield, and the drain wire, are toward the outer sleeve. The inner surface of the shield is blue. The shield is pretty-well continuous, from what I've seen.

I measured the resistance of the shield and drain wire combo, from one end to the other for a roll with almost exactly 50 feet left on it, and got 0.83 Ohms, after subtracting the resistance of the shorted probes (Tektronix DMM916).

If you try to send current through the drain wire, the entire screen surface should carry some amount of current. Current does not follow the path of least resistance. It follows all paths, in inverse proportion to their resistances.

I have no idea how much current you could safely try to send by that route. But Belden should have the data you need.

- Tom Gootee

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Reply to
tomg

Base the current rating on that of a single copper wire of the same size.

Reply to
Robert Baer

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