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#161361 - 04/02/07 05:56 AM Urban legend?
Tom Offline
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Registered: 01/01/01
Posts: 1044
Loc: Shinnston, WV USA
Over the years and from several sources, I've heard that there is some type of tester that can be connected to a ground rod and the tester will indicate how long the rod is.

I've never seen this in any of the test equipment catalogs I have. Anyone ever actually seen one and can you name the manufacturer?
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#161365 - 04/02/07 07:11 AM Re: Urban legend? [Re: Tom]
electech Offline
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Registered: 02/18/02
Posts: 113
Loc: Northern Il
A tape measure?


Sorry, but I just couldn't stop myself!
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#161372 - 04/02/07 08:43 AM Re: Urban legend? [Re: electech]
dougwells Offline


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Registered: 05/03/03
Posts: 1137
Loc: kamloops BC Canada
the rods in Canada are stamped on the side close to the top what length they are.
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#161378 - 04/02/07 10:02 AM Re: Urban legend? [Re: dougwells]
Tom Offline
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Registered: 01/01/01
Posts: 1044
Loc: Shinnston, WV USA
Rods that are listed by UL are marked within the top 12 inches. But more than one person has told me that "a guy from the power company came along and hooked something up to the rod & told me that I cut off (insert number)" and they were all amazed at how close the number was to wehat they did cut off the rod.

So, does such an electrical tester exist? I usually look for saw marks on the end of the rod, but some people are actually smart enough to hammer these off. Be nice to have this tester if it exists & doesn't cost too much.
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#161387 - 04/02/07 12:28 PM Re: Urban legend? [Re: Tom]
renosteinke Offline
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Registered: 01/22/05
Posts: 5316
Loc: Blue Collar Country
I think I know of the type of tester that you are hearing about. For the life of me, however, I can't recall the proper name; I was looking into something similar a few years ago, but was scared off by the price.

I had a feeder to a mobile home that had developed a fault somewhere along it's 300 ft. length. As you might guess, I was not looking forward to all that digging!

As I recall, this type of $3000 circuit tracer sends an impulse down the wire, then listens for the returning echo. From the time delay, it calculates the distance. Such a device could, conceivably tell you how long a ground rod was.

A possible solution MIGHT be the Amprobe AT-2005, with the T 2200 transmitter and A2201CE clamp attachment.

This is just 'book learning;' I have not actually used these things.
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#161391 - 04/02/07 01:01 PM Re: Urban legend? [Re: renosteinke]
SolarPowered Offline
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Registered: 07/05/04
Posts: 625
Loc: Palo Alto, CA, USA
Originally Posted By renosteinke

As I recall, this type of $3000 circuit tracer sends an impulse down the wire, then listens for the returning echo. From the time delay, it calculates the distance. Such a device could, conceivably tell you how long a ground rod was.

What you are describing is a Time-Domain Reflectometer.
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#161401 - 04/02/07 04:04 PM Re: Urban legend? [Re: SolarPowered]
SteveFehr Offline
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Registered: 03/19/05
Posts: 1195
Loc: Chesapeake, VA
Yep, TDR.
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#161402 - 04/02/07 04:17 PM Re: Urban legend? [Re: SteveFehr]
hbiss Offline
Member
Registered: 12/16/03
Posts: 886
Loc: Hawthorne, NY USA
There is no way to tell the length of a ground rod. You can measure the resistance but that's only going to tell you the resistance of the soil. A TDR, well that's going to tell you nothing at all.

So, yes this is a urban legend.

-Hal
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#161404 - 04/02/07 05:00 PM Re: Urban legend? [Re: Tom]
e57 Offline
Member
Registered: 05/27/03
Posts: 2876
Loc: S.F.,CA USA
I have an 'inexpensive' TDR, and a while back had access to an expensive one. And I don't think you could do it with one... It needs two conductors... But if you had some sort of referance rod - MIGHT..... But dont think it would be too accurate through soil... There may be some other type of tool that works on the same principle. Megger makes some other stuff and they are the big guys of that type of test gear...
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#161407 - 04/02/07 05:41 PM Re: Urban legend? [Re: e57]
RobbieD Offline
Member
Registered: 02/23/03
Posts: 231
Loc: Canada
The only thing that I can think of is using a ground penetrating radar device. The device has a screen that would show you the outline of the ground rod and to the depth that it is driven. Same thing that the guys from Mythbusters used to try and find the remains of Jimmy Hoffa in some sports stadium. Using one of these would not be very practical for you purpose though.

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