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OT - Dumb question re metal detectors and buried wires.

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  • CarlByrns
    replied
    Good irrigation contractors use wire locators- they are not cheap (I sell them) but you can have a contractor map out your property in an hour or so. Some golf courses have their own wire detectors (if you know a superintendent). Some rental houses have them, but be sure they offer instruction on how to use one.

    Wire locators do not work like metal detectors- they require an active signal (very high voltage) and a ground rod. They are very accurate.

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  • strokersix
    replied
    Originally posted by rdfeil View Post
    Now to address something mentioned above about live line location on the cheep. If you have a "electrically noisy" item. Think a large drill with sparking brushes or the like. You can definately use an old battery powered portable AM radio. Start the drill and go to the farthest distance where you KNOW the line is. Tune the AM radio for the most noise as far away from actual stations as you can. Confirm the noise by turning off the noise source. When you have it confirmed, turn on the noise again. Now comes the tricky part. Slowly wave, rotate, raise and lower the radio while listening to the noise from the speaker. You will find a peak AND a null depending on the position of the radio. They will not be real great or sharp as the antenna and source are not tuned to each other like a locator is. It works better if you put the radio in the end of a 3 or 4 foot wood pole to remove your body from the antenna physics. If you play a bit you will quickly get a feel for it. This will give you a general idea where things are within a foot or two in a yard environment. Give it a try if you have the stuff on hand. Cost is zero and you may have some fun while waiting for your metal detector to arrive 😄.
    This is awesome. Thank you!

    Leave a comment:


  • Cheap Jon
    replied
    I recall seeing a detector at my local rental shop.

    Jon
    SW Mi

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  • Rustybolt
    replied
    Dan
    I can tell you that most of what you find is junk. Pull tabs, nails. aluminum cans. Interesting note. An old really rusted nail sounds just like a silver quarter.

    Leave a comment:


  • rdfeil
    replied
    Jerry is very close to the way the professional cable locators work. I have used several models from $2000 to $50000 each and honestly I liked the lower priced ones better. The more cost the more features to confuse the issue. In general, the pro models send a low frequency signal down the line. It is pulsed at about 500 to 1000 hertz to produce the audio you hear in the detector unit. I am not sure of the carrier frequency, but I suspect somewhere around 75Khz. The detector unit either has a loop antenna built into the handheld unit or a loop antenna on a pole to make it easier to wave around. I have found that using the peak finding mode first helps to locate general line run direction, but it is VERY prone to cross coupling confusion with other wires in the same trench bundle. Once general area is found, switching to null detection will increase accuracy, depth and distance by a factor of 25 minimum. The null cutoff of a loop antenna is extremely sharp and well built loop antennas can null within fractions of an inch of alignment.
    Now to address something mentioned above about live line location on the cheep. If you have a "electrically noisy" item. Think a large drill with sparking brushes or the like. You can definately use an old battery powered portable AM radio. Start the drill and go to the farthest distance where you KNOW the line is. Tune the AM radio for the most noise as far away from actual stations as you can. Confirm the noise by turning off the noise source. When you have it confirmed, turn on the noise again. Now comes the tricky part. Slowly wave, rotate, raise and lower the radio while listening to the noise from the speaker. You will find a peak AND a null depending on the position of the radio. They will not be real great or sharp as the antenna and source are not tuned to each other like a locator is. It works better if you put the radio in the end of a 3 or 4 foot wood pole to remove your body from the antenna physics. If you play a bit you will quickly get a feel for it. This will give you a general idea where things are within a foot or two in a yard environment. Give it a try if you have the stuff on hand. Cost is zero and you may have some fun while waiting for your metal detector to arrive 😄.

    Leave a comment:


  • Paul Alciatore
    replied
    If all you want to do is pull it out of the ground so you can sell it as scrap copper, why do you need to know the path in advance? Start at the source and make sure the wire is dead. Dig down and follow it as it goes across the land. If you hit a place where you can not dig, go to the other side and dig to find it again and continue following it. If only a short distance is not accessible, you may be able to just pull it out from one end or the other.

    PS: This suggestion, as well as following it with a metal detector both rely on it being direct burial cable. If it is in metal conduit, all bets are off. But if it is in metal conduit, pulling it out from one end may be easy. Or not. Been there, done that, NO FUN!

    Leave a comment:


  • J Tiers
    replied
    if you run pulsed DC down the wire, using an earth return (through the earth, not a wire), then you should be able to detect and locate to a considerable distance using a loop antenna. The plane of the antenna would point at the wire when the signal is maximum..

    That could be used also to triangulate the distance down that the wire is.

    If you prefer a "null" to a maximum, then you can use the loop antenna with it's plane perpendicular to the wire. It will null out when the antenna has it's center of area exactly over the wire.

    Leave a comment:


  • darryl
    replied
    The typical metal detector responds to metals about as deep as the search coil is in diameter. Which means that the larger the search coil, the deeper it can detect. At the same time it detects everything within its area, so it becomes more difficult to zero in on something.

    To detect buried wiring you make the wiring noisy, then detect that noise. I haven't searched lately, but I think you would find a suitable detector made just for wiring. I don't see why such a thing should not be available-

    Leave a comment:


  • gambler
    replied
    https://www.detectorprospector.com/m...ctor-database/ all the info you'll ever need on detectors,( i have 2). you will become addicted.

    Leave a comment:


  • Dan Dubeau
    replied
    Originally posted by Rustybolt View Post
    Yes and no. It's easier for them to find wires that electricity is running through . Also it depends on the depth and soil conditions. Even though my MacoRacer will detect a quarter at 16 inches the conditions have to be just right. You might just be better off hiring a company that specializes in what you want. Then again spend 500t0 1000 dollars on a metal detector and you never know what treasures lurk benieth your lawn.
    Part of me wants to buy one for that reason. Back in the early 1900's on the township plot there are 2 buildings shown out in my back field. What was a 100acre parcel split 50/50 n-s, is now a 60/40 (mine) split e-w. I'd love to go exploring around where those building were shown and see what I could find.

    Would also be handy to find metal in logs before running them through the sawmill (when I finish it).

    That's it, just talked myself into buying one lol.
    Last edited by Dan Dubeau; 04-24-2022, 03:55 PM.

    Leave a comment:


  • Rustybolt
    replied
    Yes and no. It's easier for them to find wires that electricity is running through . Also it depends on the depth and soil conditions. Even though my MacoRacer will detect a quarter at 16 inches the conditions have to be just right. You might just be better off hiring a company that specializes in what you want. Then again spend 500t0 1000 dollars on a metal detector and you never know what treasures lurk benieth your lawn.

    Leave a comment:


  • Ohio Mike
    replied
    As noted utility locating / 811 will only mark public utilities. If you have privately owned power/phone/data wires between buildings you are out of luck. There are however private locating contractors that can come out and mark these for you.

    Leave a comment:


  • ChazC
    replied
    Originally posted by mochinist View Post
    It used to be called blue stakes here in AZ, I guess it is 811 now. Its free. https://call811.com/Start-Here/Homeowners
    Utility Locating Service (OneCall in PA) only marks recorded locations of public (power company, cable, phone, water & sewer), not private utilities and doesn't (at least in my experience in construction) do anything more than mark what the utility company's drawings show. Once the free service is complete, most contractors these days use a high-pressure water wand to "poke around" in shallow trenches and find out where everything really is. Or, they use GPR and the wand.

    Leave a comment:


  • Jon Heron
    replied
    Yep a locator is what you need, a metal detector wont cut it.
    You may be able to rent one if your near the big ****ty.
    Cheers,
    Jon

    Leave a comment:


  • rdfeil
    replied
    What you need is a cable locator as said above. I have located miles and miles of buried cables and located insulation faults on the same. The equipment varies in cost from expensive to outrageous. If you can find a telephone service person, they may be able to help. After hours for a donation or a case of beer.... The locators work in different ways. Some trace the AC power in the active wire. The best inject a signal into the wire either by a direct connection or by a clamp on coupling. The clamp on can be used on live wires. The tracker is a handheld unit or a unit with a probe. As you wave the unit over the wire it will either show a peek or a dip on a meter and the audio beep will either grow louder or quieter as the unit passes over the wire. You can determine depth by marking the location of the wire then angling the detector 45 degrees and moving sideways from the wire location. when the peek or null happens the distance between the two locations is the depth. Simple right triangle geometry. The units I have can locate within an inch side to side and depth within a few inches when held by hand. I have located cables buried over 5 feet deep some under concrete and over a mile long from the signal injector. A cable like Dan describes is a 10 minute job or less. It is like machining... right tools for the job and the tools are not cheep!! Some electricians have this equipment also. Ash around, you might get lucky.

    Leave a comment:

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