I have a circuit in my house with a funny characteristic, and I’d like to track it down. In that circuit, I measure a slight voltage difference between power and neutral at a light fixture when the switch to that fixture is off. Yet, my meter shows no continuity when I try to measure resistance. Other circuits do not show any voltage when they are switched off.<!—-> <!—-><!—->
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I assume this means that the neutral on the peculiar circuit is not at a common ground with the ‘real’ ground. It does not strike me as inherently dangerous, yet it seems like I might as well sort out the problem. Anybody seen this and have a recommendation on troubleshooting?<!—-> <!—->
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thanks,<!—-> <!—->
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Steve<!—-><!—->
Replies
Probably your meter is picking up stray votage. No problem.
Most likely the nuetral got crossed or is being shared with another circuite that still has a load on it.
Turn off other circuites one at a time untill it the low voltage goes away. trace both circuites untill you find where they meet. You will find the neutral problem at that point.
Dave
Put a light bulb in that fixture and see what it reads them.
I put a bulb in one side of the double-bulb fixture in question, and no longer measure the slight voltage in the other side of the fixture. I guess then this could mean I have a slight induced current in that circuit?
I still have to test the other circuits for a hsared neutral as suggested above.
I'm using a 20 year old analog multimeter.
thanks,
Steve
The stray voltage is due to capacitive pickup between wires. Nothing to worry about.Presumably your analog meter is either a high-impedance (ca 20K ohms/volt) mechanical meter or the transistorized equivalent of a VTVM -- usually 100K ohms/volt or better. These are sensitive enough to read the capacitive pickup. A cheapie 1K ohms/volt unit generally won't be that sensitive. (You might see the needle barely jump at best.)If you happen to have a good length (30 feet or so) of romex laying around, try this little experiment: Attach a 3-prong plug to one end, attaching the black and ground wires the way they should be (black on brass, ground on green), but leaving the white wire unconnected. Then strip back a few inches of the other end. Plug it in. Meter between black and ground and you should see 120V. (If not then something is miswired.) Then meter between white and ground. With a high-impedance meter you'll see anywhere from about 10V to about 60V, depending on the meter and the length of wire used.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
Stray voltage on a high-impedance meter.