Re: very low voltage -- dangerous?

Floyd L. Davidson wrote:
bud-- <remove.budnews@xxxxxxx> wrote:
Floyd L. Davidson wrote:
If you see voltage under
these circumstances _then_ you have a problem of some sort. As others
have pointed out, you can not blindly rely upon a high-impedance meter
in home-wiring situations since they can measure capacitive leakage
across open contacts and between adjacent conductors.
It isn't "capacitive leakage", either across open
contacts or between adjacent conductors. It's
induction.

You get induction from a magnetic field. You get a magnetic field from
current. To get induction you need a very near conductor with relatively
high current.

Not necessarily "very near". In fact in a lot of places
it's just about impossible to escape induction of power
line current into almost any other conductor, simply
because power wiring, and hence the fields from it, are
ubiquitous.

Certainly good for hum pickup in audio circuits. The OP originally reported millivolts, which could be induction. Later post was about 1V which sounds high for induction. Most posts are more like 20V or higher which I don't think is possible with induction. Magnetic fields in one wire are almost entirely canceled by the opposite field in the adjacent return wire. If misswired with the 'supply' and 'return' taking different paths, at high current the 'loop' can reportedly produce a magnetic field that can screw up the picture on a CRT near the loop.

Capacitive leakage you need a very near conductor with voltage,
producing an electric field. I agree with John that the source of
phantom voltage is likely capacitive.

Where is this very near conductor? It has to be *very* near!
(Okay, it could also be very large... ;-)

A common source is probably a run to a switch which is only hot feed and switched return. In any case, wires in the same cable or pipe.

--
bud--

.

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