Anybody got any experience with a Rapitest Power Detector? It's one of those
"voltsticks" designed to find out if a wire is live or not (but it's NOT
designed to find wires in walls - that's a different device; this one is
designed to be used on wires you have access to so you can test for breaks).

I got one to test my wiring and noticed a curious thing. When held in front
of a socket, on some sockets it beeps, but on others it doesn't. Yet those
sockets are definitely live and working. On some sockets the L beeps but the
N doesn't! Again, the sockets are normally work fine (I've opened them up
and the wires are correct inside).

Could this be indicative of a break in the ring main at some point? What do
these things actually detect, anyway?

I'd like to know as well. I just found out the same on a socket that I
just fitted. I plugged in a socket tester and all looks ok. The only
difference is that this new socket I refer to has a metal front plate
which is earthed.

Antony

Brian wrote:

Could this be indicative of a break in the ring main at some point? What do
these things actually detect, anyway?

It is indicative of what happens when you use an unreliable method of
detection ;-)



--
Cheers,

John.

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In article , Brian
writes

Anybody got any experience with a Rapitest Power Detector?

I have a Rapitest socket tester and was so impressed with it [1] that I
prefixed the model name with a "C" using tippex.

[1] i.e. not

"Brian" wrote in message
...
Anybody got any experience with a Rapitest Power Detector? It's one of
those
"voltsticks" designed to find out if a wire is live or not (but it's NOT
designed to find wires in walls - that's a different device; this one is
designed to be used on wires you have access to so you can test for
breaks).

I got one to test my wiring and noticed a curious thing. When held in
front
of a socket, on some sockets it beeps, but on others it doesn't. Yet those
sockets are definitely live and working. On some sockets the L beeps but
the
N doesn't! Again, the sockets are normally work fine (I've opened them up
and the wires are correct inside).

Could this be indicative of a break in the ring main at some point? What
do
these things actually detect, anyway?


Your first paragraph says it all - it's useful to see if a circuit is live
and then dead when you remove the fuse/trip, etc. but can be misleading in
some circumstances. Don't rely on it if you are sticking your fingers in
and it's no substitute for proper test equipment.

Peter

antgel wrote in message
oups.com...
I'd like to know as well. I just found out the same on a socket that I
just fitted. I plugged in a socket tester and all looks ok. The only
difference is that this new socket I refer to has a metal front plate
which is earthed.

That's probably the answer - that the earth plate somehow affects the
reading.

Brian wrote:

Anybody got any experience with a Rapitest Power Detector? It's one of
those "voltsticks" designed to find out if a wire is live or not ... What
do these things actually detect, anyway?

Electric field: they're basically an amplifier with a very high input
impedance ( tens of megohms) and probably bandwidth of c. 100Hz driving a
rectifier and LED and/or buzzer. Or something like that. Thus if you hold
it near a conductor at around 240V 50Hz AC (i.e. mains) it'll pick up
enough voltage from the electrical field for the amplifier to drive the
indicator. You'd get much the same effect connecting a wire to the
high-impedance input of an old-fashioned amplifier for a crystal mic or
record pickup and waving it around, giving a bloody great mains hum from
the speakers when the wire is near a mains conductor.

Limitations a

it won't pick up so much if there are earthed conductors nearby, especially
between the live conductor and the voltstick (false negative)

it can pick up induced voltages from adjacent conductors so that a conductor
that is not connected to anything but is near a live conductor somewhere
along its length can appear to be live when tested with the voltstick
(false +ve)