My trusty electrical screwdriver lit up (dimly) on the switched live wire to our kitchen lights. So I checked it with a multi meter and it shows 5 volts ac between live and neutral when the light switch is in the off position. How is that possible? Is this potentially dangerous? Do I need to take any action? The kitchen light seems to work without problem.
There is no such thing as a *trusty* neon-screwdriver
Most likely picking up an induced voltage from a parallel conductor, digital multimeter has such a high impedance so will not drain the charge, an analogue meter would probably show nothing.
No, there will be virtually zero current available.
If you're unlucky and you use CFLs you might get the occasional flicker from then when turned off as they may occasionally manage to charge an internal capacitor.
There is no such thing as a trusty electrical screwdriver. They are the most dangerous tool ever invented... Capable of both false negatives and false positives, *and* having the ability to kill you if they get damp.
To answer your question though, the voltage you are seeing will almost certainly be being induced into the cable where it runs alongside other live cables and is nothing to worry about.
Is the voltage present with a load in place (the light bulb).
Steve
Really? How can they kill? And how can they be sold if they are sooooo dangerous?
Matt
1) There is no way to know if they are actually working properly. You could 'test' a circuit, not have the neon illuminate and assume the circuit is safe. Electrocution follows shortly afterwards. Although it must be pointed out that this isn't a direct result of the tool, rather from flawed diagnostic techniques. 2) Moisture. Most of the neon screwdrivers use either a single resistor or a block of semi-conductive foam between the pad on the back and the neon lamp. Lets say your screwdriver gets soaked right through somehow and is full of water without you noticing it. The rest is obvious.
They really are stupid devices and shouldn't be used - indeed, shouldn't be sold...
ps. your post was reeeeeeaaalllyy condescending...
We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember stevelup saying something like:
People still buy them out of sheer handiness, but it's not a recommendation. I've been using voltstiks for a couple of years and find them better all round. A decent voltstik like the Fluke one is better than some others, as it is fairly selective and needs to be close to a wire or connnector, while some of the other ones light up within inches of a live conductor, which is useless sometimes.
The annual electrocution death rate shows they arent particularly dangerous, but theyre certainly not safe tools. Surely no grown up thinks unsafe tools arent sold.
NT
Indeed. Hammers are dangerous if swung at someone's head, yet it is obvious that this is not an appropriate use of a hammer.
The difference with the neon tester screwdrivers is that they are unsafe if you use them in the way they *are* intended to be used. It is not at all obvious that they are unsafe which is why I do not understand them being on sale in the first place.
Steve
Even if it were a low impedance source, that could supply 100s of amps, there's insufficient voltage to be at all dangerous.
MBQ
It's the volts that jolts, but the mill*s that kills.
If there aren't enough volts, there wont BE any mills. Try ohm law.
MBQ
Why do voltsticks light up when you wave them about quickly?
Or is my voltstick didgy?
We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "The Medway Handyman" saying something like:
Dunno.
Has it got holes and can you play a tune on it?
But as long as you test for a positive every single time you rely on a negative they aren't that risky.
*We* all know to do that, of course. The people at risk are those who don't know.
It do :-)
The message
from snipped-for-privacy@care2.com contains these words:
Surely the phrase "safe tools" is something of an oxymoron?
If there aren't enough volts, there wont BE any mills. Try ohm law.
MBQ
Might explain why you work at B&Q and use (broken) Google groups, brainless... :~(
One could have one volt but enough amps to kill an elephant.
snipped-for-privacy@o77g2000hsf.googlegroups.com...
Those who live in glasshouses should not throw stones.
1) Never seen a more bizarre way of quoting - and certainly not how it is normally done on usenet (broken Google ones or not!). 2) Could you explain exactly how one volt could possibly kill an elephant at any amount of current.
messagenews: snipped-for-privacy@o77g2000hsf.googlegroups.com...
Those who live in glasshouses should not throw stones.
1) Never seen a more bizarre way of quoting - and certainly not how it is normally done on usenet (broken Google ones or not!). 2) Could you explain exactly how one volt could possibly kill an elephant at any amount of current.It's not the volts that kill but the current (amps).
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.