Finding My Invisible Dog Fence, How Much Detector Do I Need?

[Tron]

5 minutes ago, GotAU? said:

You could put the dog collar on and run around the yard mapping it out that way…just kidding!

Funny you should mention that, that's exactly how my wife tried mapping it out yesterday. Not wearing it, but holding it, obviously. To train the dog that's sufficient, but as the collar goes off a ways before the wire, that leaves an unknown of at least 10 feet or so.

[Tron]

1 hour ago, MD4V.org said:

You could even go with the Minelab Voyager

https://usa.minelab.com/x-terra-voyager 

Thanks, that would still be in the acceptable price range.

[GotAU?]

2 minutes ago, Tron said:

Funny you should mention that, that's exactly how my wife tried mapping it out yesterday. Not wearing it, but holding it, obviously. To train the dog that's sufficient, but as the collar goes off a ways before the wire, that leaves an unknown of at least 10 feet or so.

You volunteered your wife to do it? Well, it was a good try anyway! 🙂

 I didn’t realize they would sound off before you even hit the wire. Well, hope it works out for you, sounds like there are some good suggestions here. Post what works for the rest of us!

[PimentoUK]

Quote:" If the search coil has a diameter of, say, 10"/25cm, that would give a copper volume of 16.5cm^3 or 1.84g of copper underneath the search coil."


It doesn't work like that, unfortunately.Detectors require CIRCULATING currents to flow. In a thin object like a wire, they can only circulate in tiny loops within the wire. It doesn't matter how long thw wire is, currents don't flow down it. That's why making a big complete loop is ESSENTAIL for your search. Currents can then circulate around that big loop.

[ I have some test coils of enamelled copper wire, for techy uses like testing / repairing detectors. Typically, 100 turns of 0.25mm diameter ECW, about 50mm diameter loop, about 10 grams of copper there. I can wave these right up against the bottom of my detector search-coil, without a sniff of a signal. My hand gives more of a signal ( because it's composed of lots of salty electrically-conductive water )]

[Johnnysalami1957]

14 minutes ago, Tron said:

The thing is that especially the weather-station cable is hardwired, so it would be quite a hassle to disconnect and reconnect everything to inject the frequency for a cable finder. Thus the idea of a metal detector.

To give you some numbers, the cable is 12AWG (total overkill, I know), so 3.3 mm^2, and two strands. If the search coil has a diameter of, say, 10"/25cm, that would give a copper volume of 16.5cm^3 or 1.84g of copper underneath the search coil.

I've read people frequently find iron/aluminum bottle caps and can tabs, which weigh probably in the same ballpark...

Use a handheld pinpointer duct taped to a broom handle. Once you find it, just follow it with the pinpointer and line of sight it to the other end. Or at night put 100 amps on it and look for the glowing line in the lawn. No don't do that!

[Tron]

27 minutes ago, PimentoUK said:

Detectors require CIRCULATING currents to flow.

Ah, so like the induction of an eddy current into the target? That makes sense, then.

[Chase Goldman]

1 hour ago, Tron said:

Ah, so like the induction of an eddy current into the target? That makes sense, then.

Yep, that's the principle of how metal detectors work.  Chains, thin open looped wires (regardless of length) are notoriously difficult to detect with a metal detector because the tiny eddy current loops result in VERYWEAK fields regardless of the conductivity and mass of the target.  MD is not really the right tool for this task unless the cables are rather shallow (i.e., less than a foot deep)

[Tron]

I totally forgot that both cables are fixed to the ground with steel staples. Those are about 1/8" in diameter, approximately 2" across the top and 6" long. I surely should be able to find those, right?

[Tron]

7 minutes ago, Chase Goldman said:

MD is not really the right tool for this task unless the cables are rather shallow (i.e., less than a foot deep)

Like I said, they're on the ground, but overgrown. So an inch deep at best.

Same goes for the staples.

I might employ Amazon and order an entry-level multi-frequency detector (thinking about a vanquish-340) and just give it a try, and send it back if it doesn't work...