Using signal generation to detect the location of a line bre

[Eric Livingston]

I have three speaker wires running just behind sheetrock along a wall in my
house that have breaks in them somewhere (I believe from the contractor
firing nails through the wires when putting up the sheetrock). Two of the
wires are shorted from one end (wall terminal) and open from the other. The
third is open from both ends. I figure in all cases a nail-gunned nail went
through the wire in question, and in two cases the nail is probably shorting
one half of the wire.

I would like to detect where the breaks are in the wall.

I've tried generating emf in the shorted lines in the wall using a strong
magnet, and it works to a degree but not enough - I need a stronger magnet
or a more sensitive multimeter.

What I'm thinking now is that if I can use the wire(s) in the wall as an
antenna, generating some kind of signal, I could use a receiver held up to
the wall to detect that signal, and thus detect the break. Would this work?
How would I best do this?

Also, I've used a small electric motor as a generator to create an AC
current in the wires. This also works to a small degree even with the cut
(i.e. open) wires in the walls due to the capacitance of the wire, though
there's no closed circuit. Can I use something to detect the AC Current in
the wires behind the wall? Could this work even with the broken (not
shorted) wires, relying on nothing but the wire capacitance to allow a
trickle of AC current to get through?

Are there other ways to do what I'm trying to do? It seems like it should be
possible.

Thanks,
Eric

 

[Luhan Monat]

Eric Livingston wrote:

I have three speaker wires running just behind sheetrock along a wall in my
house that have breaks in them somewhere (I believe from the contractor
firing nails through the wires when putting up the sheetrock). Two of the
wires are shorted from one end (wall terminal) and open from the other. The
third is open from both ends. I figure in all cases a nail-gunned nail went
through the wire in question, and in two cases the nail is probably shorting
one half of the wire.

I would like to detect where the breaks are in the wall.

I've tried generating emf in the shorted lines in the wall using a strong
magnet, and it works to a degree but not enough - I need a stronger magnet
or a more sensitive multimeter.

What I'm thinking now is that if I can use the wire(s) in the wall as an
antenna, generating some kind of signal, I could use a receiver held up to
the wall to detect that signal, and thus detect the break. Would this work?
How would I best do this?

Also, I've used a small electric motor as a generator to create an AC
current in the wires. This also works to a small degree even with the cut
(i.e. open) wires in the walls due to the capacitance of the wire, though
there's no closed circuit. Can I use something to detect the AC Current in
the wires behind the wall? Could this work even with the broken (not
shorted) wires, relying on nothing but the wire capacitance to allow a
trickle of AC current to get through?

Are there other ways to do what I'm trying to do? It seems like it should be
possible.

Thanks,
Eric


Eric,

I just know I've seen a gadget made to do this very thing. When I
remember just where I saw it, I get back to you....

--
Luhan Monat, "LuhanKnows" At 'Yahoo' dot 'Com'
http://members.cox.net/berniekm
"The future is not what it used to be."

 

[John Fields]

On Sun, 16 Nov 2003 12:53:59 -0800, Luhan Monat
<shootspammers@random.com> wrote:

I just know I've seen a gadget made to do this very thing. When I
remember just where I saw it, I get back to you....

"Luhan Don't Know"?-)

--
John Fields

 

[Bob]

"Eric Livingston" <eric@thelivingstons.org> wrote in message
news:AZPtb.18353$Dw6.84071@attbi_s02...

I have three speaker wires running just behind sheetrock along a wall in
my
house that have breaks in them somewhere (I believe from the contractor
firing nails through the wires when putting up the sheetrock). Two of the
wires are shorted from one end (wall terminal) and open from the other.
The
third is open from both ends. I figure in all cases a nail-gunned nail
went
through the wire in question, and in two cases the nail is probably
shorting
one half of the wire.

I would like to detect where the breaks are in the wall.

I've tried generating emf in the shorted lines in the wall using a strong
magnet, and it works to a degree but not enough - I need a stronger magnet
or a more sensitive multimeter.

What I'm thinking now is that if I can use the wire(s) in the wall as an
antenna, generating some kind of signal, I could use a receiver held up to
the wall to detect that signal, and thus detect the break. Would this
work?
How would I best do this?

Also, I've used a small electric motor as a generator to create an AC
current in the wires. This also works to a small degree even with the cut
(i.e. open) wires in the walls due to the capacitance of the wire, though
there's no closed circuit. Can I use something to detect the AC Current in
the wires behind the wall? Could this work even with the broken (not
shorted) wires, relying on nothing but the wire capacitance to allow a
trickle of AC current to get through?

Are there other ways to do what I'm trying to do? It seems like it should
be
possible.

Thanks,
Eric

Eric,

This tone generator and probe are intended for phone lines, but it will
certainly work for you (but maybe too expensive for you). Just make sure you
disconnect as much equipment as you can before you start probing (you should
certainly disconnect the audio amplifier).

http://www.tecratools.com/pages/telecom/tonetest.html


This is the manufacturer's site:
www.tempo.textron.com