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Finding a weak or nicked spot on a buried wire

Richard England

May 8, 2022
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I have an invisible dog fence, an underground wire (boundary loop) that transmits a radio signal, and when the dog that has a receiver collar gets near it they get a shock. The transmitting unit alarms me if it detects a break in the wire. My guess is when the resistance is too high to properly transmit the signal.

The alarm went off, I measured the boundary loop and it was 13K ohms. But, if I put a 12v battery on it for a second and then test the boundary loop, it reads 2 ohms. So far this has worked a few times.

My guess is a weak spot on the wire, although I'm not sure why the jolt fixes the resistance issue.

How do I find a weak or nicked spot on a buried wire? I was thinking of blasting the wire with a high voltage to break the weak spot, then finding and fixing it should be easy.
 

Bluejets

Oct 5, 2014
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Broken or not, your only course of action would be to dig it up.
Any test equipment available would be prohibitively expensive either to buy or lease.
 

Martaine2005

May 12, 2015
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I would first check ALL visible wire from control box through door ways, near paving and any new fence posts that may have been erected.
Also for any obvious sign of ground disturbance from a mole, fox or your dog.
Cheap wire detectors/sniffers can be as little as £20 but whether they work is another story.
Not sure why applying a voltage and getting a different resistance other than possible corrosion in a previous repair joint?. Or a lengthened boundary wire?.
Or a very smart dog!!

Martin
 

Harald Kapp

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Nov 17, 2011
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If the collar has a visible indicator for activation (e.g. an LED, use the dog's collar as a sensor: trace along the wire until the collar does no longer receive the signal. Then the defect in the wire is near that point.
Of course, use the collar only without the dog ;).
 
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