Cable Locator

[dereckbc]

OK guys keep in mind I am a engineer, not an electrician. I rently bought a house with an irrigation system. One of the underground valves has an open circuit. Cannot see the coil with an ohm meter. Problem is I do not know where it is or where to dig it up.

How do I locate it without escavating the whole yard or damaging the wiring? FWIW all the pipe is PVC. Only thing to use is the control wire.

 

[bphgravity]

Re: Cable Locator

Take two short lengths of #10 copper and bend into and "L" shape. Hold one in each and point forward while walking through the yard. When the two wires rapidly separate from each other, you have found the problem, or possibly gold.

Can you just simply re=pull that circuit or "zone:, or is the whole thing looped?

 

[don_resqcapt19]

Re: Cable Locator

Dereck,
You should be able to rent cable locater instrument. One of the problems here is that the coil could be open, or the conductor could be open at any point between the house and the coil.
I have used the method suggested by Bryan, with some success. The biggest problem with that method is that you have no idea what you are finding and how deep it is.
Don

 

[dereckbc]

Re: Cable Locator

Originally posted by bphgravity:
Can you just simply re=pull that circuit or "zone:, or is the whole thing looped?

I would, but it is not that easy. All the cable is direct burried about 10 inches.

What kind of witch craft are into down in FL?

 

[peteo]

Re: Cable Locator

Just noticed your profile... Anyone you work with, who has worked installing telco or alarms, will probably have a trac a tone they'd be happy to loan you for a weekend. One ex-boss bought a mail order AM transmitter (the size of a dime!) and hooked a 555 into it, which made a terrible squeal, then we would use a transistor radio to find things. The little portable ones have a very directional antenna built right in. He found things the utility people gave up on, ten and twelve feet deep.

 

[dereckbc]

Re: Cable Locator

Well I do have a tone locator for telephone cable, but it is useless for underground location. It consist of a audible tone generator, and induction amplifier.

 

[hbiss]

Re: Cable Locator

You might play with that tone generator and probe. Connect headphones to the probe, try the generator between one conductor and ground, connect a coil to the probe tip etc.

Hmmm, the thought just occurred- if you happen to have an audio amp with a 70 volt output, drive it with the tone generator, connect the 70 volt output to the wire and crank it up. They (Progressive) do make high powered tone generators for outside line work that you can hear through walls in the next room.

It's only 10 inches down and I have had limited success (stress limited) doing things like this before calling in the big guns.

-Hal

[ January 24, 2006, 02:23 PM: Message edited by: hbiss ]

 

[dereckbc]

Re: Cable Locator

Originally posted by hbiss:
Connect headphones to the probe

How? I think you know the instrument I am referring too. The tone generator is just a simple black box with a DPDT switch. One posistion is 9-volt talk battery, and the other is the two-tone generator.

The induction amp is a probe with a button and built-in speaker. I assume you mean just bridge accross the speaker with a set of headphones.

 

[hbiss]

Re: Cable Locator

No, most probes have provisions to clip a butt set to it. I have seen "ears" with contacts on them and simple screws sticking out the back.

All kinds of these things out there today, some better than others. Maybe yours doesn't have this provision.

-Hal