Quote:
|
Would you agree that non-contact testers can confirm that things are live but not the reverse?
|
Exactly. They are no substitute for an approved 2-pole voltage indicator and such a device (and its proving unit) is mandatory for confirming safe isolation. An AVI is reliable and predictable as it cannot accidentally be set to the wrong range, its relatively low input resistance is not fooled by capacitively-coupled 'ghost' voltages on isolated cables etc. But OTOH it's only any good when you have a circuit. A hypothetical light switch with permanent line, switched line feeding an empty lampholder, and a broken or absent CPC, creates a situation where an electrician might test between each conductor and each other, get no readings and assume dead, when in fact it is still fully live. In this situation, the non-contact indicator is a lifesaver, as the missing earth / neutral reference is replaced by the user's stray capacitance. The same is technically true of the neon screwdriver, although they have reliability and insulation integrity issues that make them a very poor second to the non-contact.
A situation where the Voltstick wins hands down, is testing a cable that is about to be cut mid-span. Unless is is screened (e.g. FP or SWA) the stick will warn of it being live before disturbing it at all. Even if it is screened there is the possibility, if one has any concerns, of dissecting it to access the cores within before finally breaching their insulation. I use my Voltstick for all sorts of tricks. I managed to trouble-shoot a 3-way lighting switching fault without even opening the switches up. I knew which of the three had a bad connection by following the pattern of live and dead metal behind the faceplate. Tracing breaks in Socapex lighting multicores strapped along trusses flown high over the stage - you don't want to be up there longer than necessary - with the ability to follow individual live and neutral cores through the sheath of an 18-core YY.
But I digress.