gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
080410-1845 EST USA
MrHopper:
Probably your best reference point is the cooper water line from the street. Current measurements are useful, but in addition voltage measurements might help you track the source, especially if the source is some how thru the earth.
Connect an insulated wire to the water line before the meter. #20 or #18 would be convenient. Make a test probe and connect the meter between the wire from the water pipe and the probe. Assume you may find a moderate to high voltage with the probe. Thus, appropriately insulate yourself. It should be obvious you need a long wire. A Fluke voltmeter will be a very high input impedance and therefore not much probe contact should be required.
Now use the probe to check voltage anywhere you choose. A fluke meter with automatic scaling may be useful. This probe provides a means to measure the potential of the yard at various places. If the voltage rises as you move away from the building, then there is a current flow thru the soil. Voltage measurements relative to the distance from the building may point you in the direction of the source.
You can probe the walls of the basement, various different metal objects, and this other old service nuetral and see if anything is obvious.
Typical 8' ground rod to ground rod resistance in a moist clay soil may be around 10 ohms. Tests I have run over a 30' distance fall in this range. There is substantial voltage drop at the interface of the rod with the earth. 120 V and 10 ohms produces 12 A.
Probe the pipe or conduit that you said produced a spark with that joint open. The voltage may tell you something.
Be careful because you may find a hot source somewhere.
At this time with the information you have so far it is hard to tell if voltage probing will help.
.
MrHopper:
Probably your best reference point is the cooper water line from the street. Current measurements are useful, but in addition voltage measurements might help you track the source, especially if the source is some how thru the earth.
Connect an insulated wire to the water line before the meter. #20 or #18 would be convenient. Make a test probe and connect the meter between the wire from the water pipe and the probe. Assume you may find a moderate to high voltage with the probe. Thus, appropriately insulate yourself. It should be obvious you need a long wire. A Fluke voltmeter will be a very high input impedance and therefore not much probe contact should be required.
Now use the probe to check voltage anywhere you choose. A fluke meter with automatic scaling may be useful. This probe provides a means to measure the potential of the yard at various places. If the voltage rises as you move away from the building, then there is a current flow thru the soil. Voltage measurements relative to the distance from the building may point you in the direction of the source.
You can probe the walls of the basement, various different metal objects, and this other old service nuetral and see if anything is obvious.
Typical 8' ground rod to ground rod resistance in a moist clay soil may be around 10 ohms. Tests I have run over a 30' distance fall in this range. There is substantial voltage drop at the interface of the rod with the earth. 120 V and 10 ohms produces 12 A.
Probe the pipe or conduit that you said produced a spark with that joint open. The voltage may tell you something.
Be careful because you may find a hot source somewhere.
At this time with the information you have so far it is hard to tell if voltage probing will help.
.
