Should I be worried or not? I've got quite a lot of metal faced
plugs / switches, and this weekend whilst generally pottering around I
happened to touch my voltage testing screwdriver to one of these
plates and discovered that it was showing something around 12v. This
was consistent then across all of the other faceplates that I touched
with it. I took the switch off and found that I got the same result
on the earth cable.

The device I used was the little red screwdriver in this item (http://
tinyurl.com/32xxka (links to B&Q)) which displayed a flickering 12V
symbol.

Is this normal?

Matt

wrote:

Should I be worried or not?

Probably not...

I've got quite a lot of metal faced
plugs / switches, and this weekend whilst generally pottering around I
happened to touch my voltage testing screwdriver to one of these
plates and discovered that it was showing something around 12v. This

Voltages must be measured relative to something - i.e. they are
potential differences, rather than absolute numbers. Hence you have to
ask yourself what that 12V is relative to?

Assuming this is one of these single touch volt sticks where you only
need make one connection, the answer is that it is measuring relative to
the potential of your body. Since that is unlikely to be at true earth
potential, it does not actually tell you much about the actual potential
of your earth with respect to true earth.



--
Cheers,

John.

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On 7 Jan, 11:33, John Rumm wrote:
Voltages must be measured relative to something - i.e. they are
potential differences, rather than absolute numbers. Hence you have to
ask yourself what that 12V is relative to?

Assuming this is one of these single touch volt sticks where you only
need make one connection, the answer is that it is measuring relative to
the potential of your body. Since that is unlikely to be at true earth
potential, it does not actually tell you much about the actual potential
of your earth with respect to true earth.

John

Thanks. That's what my gut feeling was.

I did try a multi-meter out on it too and couldn't reproduce the
apparent voltage, but I'm wary of using a multimeter because to be
honest I don't really understand what I'm doing. Its great for a bit
of continuity testing and checking the odd battery, and I use this
more than the "single touch volt stick" when I really want to convince
myself that I've turned off the power if I'm swapping a switch or
something similar, but other than that I'm a complete noddy!

I kind of worked on the basis that as no-one was shouting "ouch" as
they touched the light switch that everything was likely OK!

Matt

On Mon, 07 Jan 2008 03:52:00 -0800, matthew.larkin wrote:

I kind of worked on the basis that as no-one was shouting "ouch" as
they touched the light switch that everything was likely OK!

Could it be that that was because they were dead? ;-)

--
John Stumbles

On 7 Jan, 13:43, John Stumbles wrote:
On Mon, 07 Jan 2008 03:52:00 -0800, matthew.larkin wrote:
I kind of worked on the basis that as no-one was shouting "ouch" as
they touched the light switch that everything was likely OK!

Could it be that that was because they were dead? ;-)

--
John Stumbles

Nah, I'd have definitely spotted a number of dead bodies if they were
lying the way of me getting to the plug sockets.

I'll check tonight though just to make sure

Matt

On Mon, 7 Jan 2008 03:52:00 -0800 (PST), wrote:

I did try a multi-meter out on it too and couldn't reproduce the
apparent voltage, but I'm wary of using a multimeter because to be
honest I don't really understand what I'm doing. Its great for a bit
of continuity testing and checking the odd battery, and I use this
more than the "single touch volt stick" when I really want to convince
myself that I've turned off the power if I'm swapping a switch or
something similar, but other than that I'm a complete noddy!

Probably the metalwork /is/ earthed and the measuring device is showing /you/
having the voltage. You will see the same effect if you earth one wire of your
multimeter and grab hold of the other wire.

Geo

That is perfectly normal. Try touching something earthed, with your finger
tip and seeing what reading you get on the screw driver. It is just the
surrounding ac field being picked up by your body, from the mains circuits
around you combined with a high impedance voltage measuring device (the
screwdriver).


wrote in message
...
Should I be worried or not? I've got quite a lot of metal faced
plugs / switches, and this weekend whilst generally pottering around I
happened to touch my voltage testing screwdriver to one of these
plates and discovered that it was showing something around 12v. This
was consistent then across all of the other faceplates that I touched
with it. I took the switch off and found that I got the same result
on the earth cable.

The device I used was the little red screwdriver in this item (http://
tinyurl.com/32xxka (links to B&Q)) which displayed a flickering 12V
symbol.

Is this normal?

Matt