# Fault finder



## bobbyho (Oct 15, 2007)

I use a Harris T100 to find distance to a short circuit. This is great but I was wondering if there is something that you can "wand" over the wall where the short is and it highlights exactly where the short is. for example I am going to a job now where the carpenter shot a 2" trim nail through a wire. I know within a foot or 2 of where it is. Problem is one piece of trim is baseboard painted trim the other is a piece of maple stained trim. I would love to know which particular piece it is. That is where the fault finder would be perfect


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## den (Mar 28, 2009)

The A-Frame fault finders for underground will locate within 1/4 " when all is going right. I don't know why they wouldn't work on a wall. I have used them on cement driveways and on wood decks with good results. Worth a try if you can get one to use.


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## 480sparky (Sep 20, 2007)

I seriously doubt an A-frame type fault-finder would work. They require some sort of conductive material surrounding the fault to operate. In most cases, it's the earth. Drywall & baseboard won't conduct enough current flow to allow the fault-finder to zero in on the problem.


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## den (Mar 28, 2009)

I don't really know but I thought that the a-frame fault finders worked on radio type signals. When locating, they were looking for 60 cycles for elec. and when we put the toner on we usually the 33 cycle setting as it had less interference and when the dynatel was in fault finder mode it would cycle back and forth from 33 to whatyever cycle it was using for faultfinding to allow the user to switch to locate and back to fault finding without going back to the toner box. I always tryed to ohm check the wire first to make sure I was on the right wire but they wouldn't always ohm out. I have found faults on previous splices with bad connections that were not burned thru the insulation and have found several faults going up the riser poles. One I remember was in pipe (pvc) and had been shot which just cut the wire but was not shorted out. I thought the a-frame points were just acting like antenna's which would point towards the strongest signal which got you over the signal break:001_huh:


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## 480sparky (Sep 20, 2007)

den said:


> I don't really know but I thought that the a-frame fault finders worked on radio type signals. When locating, they were looking for 60 cycles for elec. and when we put the toner on we usually the 33 cycle setting as it had less interference and when the dynatel was in fault finder mode it would cycle back and forth from 33 to whatyever cycle it was using for faultfinding to allow the user to switch to locate and back to fault finding without going back to the toner box. I always tryed to ohm check the wire first to make sure I was on the right wire but they wouldn't always ohm out. I have found faults on previous splices with bad connections that were not burned thru the insulation and have found several faults going up the riser poles. One I remember was in pipe (pvc) and had been shot which just cut the wire but was not shorted out. I thought the a-frame points were just acting like antenna's which would point towards the strongest signal which got you over the signal break:001_huh:


A-frame locators use a high-voltage DC pulse (hence the Progressive/Greelee "Pulsar") into the cable. I think the 2003 uses 1400 or 1500 volts. If the cable is faulted to the earth, the current will flow back to the transmitter through the earth, lowering voltage along the way. The A-frame is simply a DC voltmeter that measures the DC voltage between the probes.

Since the voltage drops in it's route through the earth, the probe closer to the fault will be higher, or 'positive' in respect to the other probe. The higher voltages will be closer to the fault, and can be 'followed upstream' to locate the fault.

If an RF signal was used, there would be no need for a pulsing signal, nor a need to inject a DC voltage into the line. Nor would you need to ground one of the transmitter leads.

I think you may be confusing cable locating using the 60-cycle frequency with fault locating. My Rycom locator can trace underground cables using just the 60-Hz signal inherent in buried electrical (and some telecom) cables.


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## den (Mar 28, 2009)

Thanks for the info 480. I still fail to see why I could find a fault in a broken cable that was not shorted to ground if it needed to have the return path. All of our locaters would pick up electric current on the locater wands only or with a toner box by using different frequencies and they did not have to be dirrect connected to tone the cable. The dynatel had a built in antenna and you could just set the toner over the cable to work or use the clamp or direct connect. We had 2 units that would also be fault finders with a-frames and those toner box's had a fault finder setting while the others didn't. The a-frames just hooked to the locater wands so you had directional arrows or colors. The dynatel was the only one to switch frequencies while fault finding. Our radiotech did not do that.


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## 480sparky (Sep 20, 2007)

den said:


> Thanks for the info 480. I still fail to see why I could find a fault in a broken cable that was not shorted to ground if it needed to have the return path. All of our locaters would pick up electric current on the locater wands only or with a toner box by using different frequencies and they did not have to be dirrect connected to tone the cable. The dynatel had a built in antenna and you could just set the toner over the cable to work or use the clamp or direct connect. We had 2 units that would also be fault finders with a-frames and those toner box's had a fault finder setting while the others didn't. The a-frames just hooked to the locater wands so you had directional arrows or colors. The dynatel was the only one to switch frequencies while fault finding. Our radiotech did not do that.


I don't see the need for the A-frame if you're snooping out an RF signal. A simple directional antenna would be all that's needed.

How would an RF signal 'know' when to 'exit' the cable at the fault? Would it not turn the entire cable into a transmitting antenna?


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## den (Mar 28, 2009)

I don't know how it works. I just know that I located for the poco for a lot of years and I could usually find the wire or a fault even if there was no break in the insulation. Is the wand using an rf signal when you hit the button for depth? this would work whether we used the toner box or not?


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## 480sparky (Sep 20, 2007)

den said:


> I don't know how it works. I just know that I located for the poco for a lot of years and I could usually find the wire or a fault even if there was no break in the insulation. Is the wand using an rf signal when you hit the button for depth? this would work whether we used the toner box or not?


I have no experience with Dynatels, so I can't answer to that. If you can recall the model number, I could do some digging around the 'net.

I know my Rycom has a depth button. Instructions state that it's only accurate when used in direct-connect mode (transmitter physically connected to de-energized cable), but I've gotten very close readings using just the 60-Hz signal.


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