Dave Liquorice wrote:
On Thu, 22 Jan 2004 01:34:52 -0000, Chris Oates wrote:


I tend to check the circuit I'm going to work on is live, volt
stick these days...

Maybe it's just my relatively ancient RS voltstick but I find I have to
hold it just so at the back end of the handle and hold the translucent
probe bit just so in relation to what I'm testing to get a reliable
indication. Thus I calibrate it by holding it close to a known live and
adjusting my hold to get it to light up then, without changing my grip,
move over to the conductor I'm testing.

(Then check with the neon stick and flick of the finger.)

All the same even with volt stick I still cautiously check that the
wires are dead. I suspect a voltstick wouldn't detect a (relatively)
high impedance leakage that could still make for a nasty jolt.

It should detect higher impedance leakage than necessary to light even a
neon (since the volt stick measures almost pure electric field, through
air + its plastic cap + whatever insulation is on the cable etc).
However there may well be situations where there's a live conductor
whose field is shielded by a grounded conductor: I suppose a
hypothetical example would be coax with mains on the centre & ground on
the braid. (I'm sure you'd never find anything like that in the real
world, of course :-)


John S