I was hoping someone could tell me why my contactless volt detector
detects voltage at my light fixture when the switch is off and my
multimeter tells me there is a 1volt different b/t white and black.
Should I be concerned?
I have a 15amp circuit that comes into the switch and is then passed
onto the fixture. The fixture is probably the 9th item on the circuit.
Thanks for any help or references on reading material to learn more!
The 1 volt you measured could be an induced voltage. If you put a load on it
(e.g. screw back light bulb), it would probably drop to zero. Use your
ingenuity to figure out how to put a load on it and measure the voltage at
the same time :)
The voltmeter is a high impedence device. Voltage can be induced
in the wire by the electric field where it is near other wires, but very
little current will be available. The voltmeter doesn't draw much
current, so it will display small voltage readings.
Don't worry about it - especially if it's only 1 volt.
It could mean the neutral wire is being broken by the switch to turn off the
light. That is what the contactless detector MAY be telling you. Those
things are not very reliable to tell if voltage is present. They do a good
job of telling of no voltage.
The 1 volt differance could be just an induced voltage. When a wire is next
to another wire , you have a 1 to 1 transformer. For just two wires next to
each other the ammount of current that can be drawn is in the microamps or
less. Many call this induced voltage. A voltmeter will load down this 1:1
voltage so that only a very small portion of the voltage is left. The lower
the resistance of the voltmeter, the lowr the indicated voltage. A 20 meg
ohm voltmeter may show 40 volts, a 20,000 ohm/volt (such as the old Simpson
260) may show 10 volts on the higher voltage scales. If you turn the
selector switch to a lower range, the meter pointer will stay in nearly the
same place instead of dropping much lower.
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