"Beldfoil" specs

[Tim Lamer]

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

 

[Eeyore]

The point is, I want the entire screen to carry the current, not just
the drain.

It won't, simply because it has a high resistance. It's only a very thin
layer of metalisation. If you need to carry many amps of screen current
or need vey low resistance use a traditional copper screen.

Graham

 

[Robert Baer]

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

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...

 

[John Fields]

Can someone familliar with Beldens "Beldfoil" aluminium-polyester
screening foil please tell me how it is constructed?
---
http://www.belden.com/pdfs/Cable101/Shielding.pdf
---

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?

---
It's continuously conductive, but because it's aluminum the
inevitable formation of the oxide film on the aluminum surface may
keep the drain wire from making contact continuously along its
length.

 

[[email protected]]

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

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

http://www.fullnet.com/~tomg/index.html

 

[Robert Baer]

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

http://www.fullnet.com/~tomg/index.html

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