Metal Detector - Page 1
Forum section: electronics / projects

author: bostonman
author_rank: Super Contributor
timestamp: July 28, 2023, 02:33:23 pm
content: I have an Earth ground rod somewhere close to my house on my property that was installed several years ago. Unfortunately I forgot the location nor can I find it after digging in several areas. Due to recent yard work, I'm curious whether the wire from the house to the rod has been accidentally cut.I'm thinking of using a metal detector to locate the rod (which will lead me to the wire) and assume I need a depth of 1-2 feet.Does anyone have a cheap design they've used that would accommodate this and/or do the cheap $25 handheld units on Amazon work well for this application?

author: Kleinstein
author_rank: Super Contributor
timestamp: July 28, 2023, 04:20:13 pm
content: The cheap handheld ones are usually very short range, like maybe 5-10 cm for checking for pipes or screws before drilling a hole. To a certain degree this limitation is intentional to get a local response.The wire / rod is relatively large metal, but dection at 1-2 feet depth and possibly deeper is a challange even for those detector for searching for coins and similar.One may be able to find the point of the earthing in a potentiometric way: apply some AC current (e.g. 330 Hz) between the earth and an auxliary rod. An than probe for the signal voltage at a few points around. With a sensitive detector one should get a reasonable idea where the gound connection is and if the connection is good.

author: bostonman
author_rank: Super Contributor
timestamp: July 28, 2023, 06:18:41 pm
content: I'm guessing a worst case of 1-2 feet. I remember seeing the top of it which, if I remember correctly, is for the inspector to visually see a rod. Afterwards, the rod gets hammered into the ground.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: July 28, 2023, 06:35:15 pm
content: Common metal detectors generally can't detect deeper than the diameter of the coils.The units used by utilities can do far better, up to 19' or so, but I've no idea how they manage that-https://www.schonstedt.com/products/u-locate/

author: PCB.Wiz
author_rank: Super Contributor
timestamp: July 28, 2023, 09:21:39 pm
content: Quote from: bostonman on July 28, 2023, 02:33:23 pmCan't you drive a new spike for less than $25

author: Infraviolet
author_rank: Super Contributor
timestamp: July 28, 2023, 10:55:13 pm
content: My guess is the units used by utilities aren't metal detectors, but rather ground penetrating radar or electrical current measurement between soil probes, either being similar to the types used by archaeologists looking for wall remnants and soil density differences.

author: bostonman
author_rank: Super Contributor
timestamp: July 30, 2023, 02:04:58 pm
content: QuoteThe spike isn't the issue, it's trying to locate the wire to find out if it's been cut.Since this Earth ground installation, I've had some yard work done and wonder if the wire has been cut by others. It comes out of the house, through a PVC pipe, and into the ground. Unfortunately that corner is difficult to access, so I can't trace the wire from that point out.Instead of squeezing myself in that area and trying to dig the wire to locate the direction and/or trace it, I thought maybe a quick $20 metal detector would make life easier. Since those aren't effective for the depth I may need, then maybe it's off to digging.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: July 30, 2023, 03:24:35 pm
content: Read the app notes at the link I posted. They go into great detail on finding breaks.

author: bostonman
author_rank: Super Contributor
timestamp: August 09, 2023, 05:27:31 pm
content: For a quick update, I used raw manual labor of digging. Amazingly enough, I was right on point the first time but must have been off by about an inch.After finding the rod, I connected a cable to the cold water pipe, used an ohm meter, and found a connection between the rod and pipe. So the wire hasn’t been cut after all these years and yard work

author: bostonman
author_rank: Super Contributor
timestamp: August 10, 2023, 01:18:22 am
content: I forgot to mention, the cable and tip of the rod was about 8-10" below the surface.