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Thread: Testing with a neon

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    Diamond Member AndyD's Avatar
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    Testing with a neon

    What's you take on using neon screwdrivers to test if circuits you're working on are live or not?
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    Diamond Member Justloadit's Avatar
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    It tells you that the voltage which are testing is above 90V, because that is the voltage required to excite the Neon.It does have an advantage that you do not have to lug your meter around if you are busty checking points, or maybe for safety before grabbing the wire to strip or whatever.
    Victor - Knowledge is a blessing or a curse, your current circumstances make you decide!
    Solar and LED lighting solutions - www.microsolve.co.za

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    Im not to keen on them,i do have a pen tester which i use now and then which i find is better then the neon screwdriver.

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    Diamond Member AndyD's Avatar
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    I detest the things with a passion. I saw one of my guys using one to prove a circuit was dead before working on it. I nearly needed a change of underwear. We had words and he claimed it was a legitimate way of testing, I told him it wasn't and I never want to see one on site again.
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    Diamond Member Justloadit's Avatar
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    Quote Originally Posted by AndyD View Post
    I detest the things with a passion.
    Can you give a reason for detesting this so much?
    Victor - Knowledge is a blessing or a curse, your current circumstances make you decide!
    Solar and LED lighting solutions - www.microsolve.co.za

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    Diamond Member AndyD's Avatar
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    I think my biggest issue at the time was the fact that I have provided all staff with test equipment and he wasn't using it, he actually didn't even have it on site

    There's more than one reason I hate neon indicator screwdrivers so much 1/ They're invariably poor quality and therefore unreliable. 2/ They're a screwdriver as well which means they get used and abused like any other screwdriver therefore are not a reliable tester. 3/ They're indiscriminate, they can show wires as being live because of induced voltages when they run a distance alongside other live wires when actually the wire your testing is isolated. 4/ If you're standing on insulated stepladders or even dairy crates with a piece of corrugated cardboard on top...... which seems to be the preferred apparatus nowadays especially for reaching light fittings..... then there's no guarantee you're sufficiently earthed for the neon to work, even if the wire is live it might not light up. 5/ They're just generally a kak jol if I think of any other reasons I'll add them here.

    These damn things seem to find their way into all sorts of places they don't belong. Even respectable tool manufacturers seem to use them as space fillers in packets of otherwise decent tools. I bought a beautiful set of Facom VDE screwdrivers a couple of months ago, I was drooling as I unpacked it, checking the superbly ground tips one by one, each screwdriver was a work of art in it's own right..... then I saw the neon screwdriver at the end of the row....my heart sank. The red cap was already loose and halfway off, a crack was visible in the cheap nasty opaque plastic and I hadn't even removed it from the box. What was a joyous moment had already been ruined. Problem was I couldn't stamp on it or otherwise destroy it in case I ever needed a warranty, I know the first question out of the agents mouth would be 'where's the neon that came with these? We can't take this thousand rand set back under warranty without the five cent neon screwdriver.'

    Who knows, maybe they actually want me to use the neon as a tester, then there would be a lot less chance of me being able to make a warranty claim whilst I'm laying in hospital.
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    I would never use my pen tester to make sure the circuit is dead thats just asking for trouble.

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    AndyD (26-Feb-11)

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    Diamond Member adrianh's Avatar
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    I think my biggest issue at the time was the fact that I have provided all staff with test equipment and he wasn't using it, he actually didn't even have it on site
    Who would be held responsible if he is electrocuted on the job - I suppose it would be your company?
    How easily someone is offended is directly proportional to how stupid they are.
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    So it seems that you trust your digital multimeter with your life. Well let me tell you something, I had a situation, in which I pulled my multimeter out and measured, and it showed zero Volts AC. Great I said, circuit disconnected I can do some work here. I have learnt a long time ago that even if the circuit appears dead or is dead, I still work in a manner as if it is a live circuit. Fortunately for me that day my instinct served me well, because at one stage the live and wire touched neutral and I saw a spark. I said - hang on this thing was supposed to be dead, pulled my multimeter out again, and as sure as can be it measured zero volts. The problem that I found later was that the battery died over night, however there was enough energy in the battery to make the display work.

    Now remember in a an electronic multimeter, when you measure AC, there is an electronic bridge rectifier which converts the AC into a DC voltage for the meter to measure, the lower battery voltage seemed to affect this circuitry, and when measuring AC, failed to work.

    After this day, I now do one more thing when working, after measuring with a multimeter, I generally short the live neutral and earth when I am working, so if the circuit is still live, it will trip the circuit breaker, or alternatively knock out the earth leakage - there is a current flow between Neutral and Earth, which the Earth leakage should see.

    I just want to add that fortunately the elctrical connections I work with are the lower current type, not more that 30Amps, so shorting the wires, will not arc, blow up and blind me if it was connected.
    Victor - Knowledge is a blessing or a curse, your current circumstances make you decide!
    Solar and LED lighting solutions - www.microsolve.co.za

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    AndyD (26-Feb-11)

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    Diamond Member AndyD's Avatar
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    Quote Originally Posted by adrianh View Post
    Who would be held responsible if he is electrocuted on the job - I suppose it would be your company?
    Good question, he's a qualified IE so I'm guessing he would be responsible for his own safety but I'm not entirely sure..

    Quote Originally Posted by Justloadit View Post
    .......I generally short the live neutral and earth when I am working, so if the circuit is still live, it will trip the circuit breaker, or alternatively knock out the earth leakage - there is a current flow between Neutral and Earth, which the Earth leakage should see......
    I would have mixed feelings about shorting live to earth. If the earth is anything less that perfect it might damage electronics especially anything with earth-referenced comms such as EPOS systems etc (Micros systems spring to mind); a high neutral -earth voltage would almost certainly destroy serial comms cards in systems of this nature. Also if the earth is poor (high impedance) it could cause the chassis of any appliances on the same circuit to develop a dangerously high touch voltages.

    I agree there's always a chance even the best testing equipment might let you down, I think the safest thing is to prove the tester on a known voltage before testing for real elsewhere. As you also point out, with experience you do tend to develop a way of working which prevents shocks even if the circuit is still live.

    Not really connected to the original topic but I would also like to see it in the rules that a DB should have lock-out devices inside it which fit all the circuit breakers used in it and also the door of the DB as well. I would even go so far as making it a part of the COC that these items should be present in the DB at all times. I think this would go a long way toward the safety of electricians and reducing accidental shocks when people are working on circuits.
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