sdppm wrote:

On Feb 15, 12:32 pm, "EXT" wrote:

"bud--" wrote in message

. .. sdppm wrote:

I wired up some lights with a dimmer switch. When I have the switch in
the off position I am still showing 67 volts. That is accross the
Netural( White) and the Load (Black) Wire. If I measure between the
netural and ground it is Zero and if I measure between the Load and
ground I get 67 volts. Where have I gone wrong. Thanks for the help

A common question. You are probably measuring with a good digital meter.
You are seeing a "phantom voltage". There is capacitive coupling - as
between a hot wire and switched wire to and from the switch. This produces
a very small current, but produces a reading on a good high resistance
meter. A light bulb with pigtail leads will indicate if voltage is
actually present.

If it is phantom voltage being measured by a sensitive meter, you can often
prove it by measuring voltage between your left hand and your right hand.
They can be that sensitive.

I trust that's not intended to mean that he uses his hand to hand
(through the chest) boody resistance to load the circuit he's measuring.
That could be problematic if there really happens to be a low impedance
source behind that voltage. G


You keep talking about the digital meters and there sensitivity. Would
I be better off with the old type meter and would the reading be more
true

A digital meter DOES give you a true reading of the voltage across it's
input leads. AAMOF it gives you a TRUER reading of the value of the
voltage source than a lower impedance meter will when the source
impedance is high.

It just won't put enough of a load across what it's connected to to
prevent miniscule currents flowing through capacitive coupling (or
sometimes leakage resistance) from creating a significant voltage across
the meter's very high input resistance. That's what's taken on the name
"phantom voltage".

As suggested above, connect a light bulb (A 6 watt incandescent night
lite will do fine.) in parallel with the meter's input leads and see
what it reads then in your particular situation.

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.