Electrical Test screwdriver mystery

[electronicsuk]

Another theory - you were live and the neutral and earth were providing a return path! Unlikely as I think you might have noticed that, but it doesn't take a lot of current nor a particularly high voltage to light those neons...

 

[daverk]

Another theory - you were live and the neutral and earth were providing a return path! Unlikely as I think you might have noticed that, but it doesn't take a lot of current nor a particularly high voltage to light those neons...

Could be. I still think that the humidity had something to do with it. Anyhow, I think I'll ditch the neon screwdiver, get a voltage indicator/test lamp, and I'm thinking of doing a City & Guilds too. Thanks for being constructive about this, it's appreciated.

 

[EFLImpudence]

Hi, I'm new to the site so may I attempt to answer a not too important or safety related question.
With this type of test screwdriver you do not touch the end of it to test for voltage - only for continuity, testing fuses etc.

 

[electronicsuk]

Hi, I'm new to the site so may I attempt to answer a not too important or safety related question.
With this type of test screwdriver you do not touch the end of it to test for voltage - only for continuity, testing fuses etc.

Interesting theory. OP, does the screwdriver contain a battery and an LED rather than a neon? I've seen and even had the pleasure of using one of these once, and AFAIK there's no way to tell any difference between the indication of continuity or voltage. What's more, it seems practically anything that conducts even a little (like 10KOhm or so) will show up continuity. So, if you were using one of these and were rather well earthed yourself, it's perfectly possible the continuity indicator could have lit.

 

[daverk]

Hi, I'm new to the site so may I attempt to answer a not too important or safety related question.
With this type of test screwdriver you do not touch the end of it to test for voltage - only for continuity, testing fuses etc.

Interesting theory. OP, does the screwdriver contain a battery and an LED rather than a neon? I've seen and even had the pleasure of using one of these once, and AFAIK there's no way to tell any difference between the indication of continuity or voltage. What's more, it seems practically anything that conducts even a little (like 10KOhm or so) will show up continuity. So, if you were using one of these and were rather well earthed yourself, it's perfectly possible the continuity indicator could have lit.

Definitely doesn't contain a battery, and I presume it truly is a neon - it has a 'filament'-shaped light which illuminates when the blade is placed on a mains voltage, and it is a bit dimmer if you take the thumb off the button.

I doubt if I was particularly well earthed, lying prone in the loftspace on fibreglass and wooden ceiling joists, but it was very humid.

I don''t touch the blade end of it for obvious reasons. I have only ever used it to test for the presence of a voltage, as an indicator (1) to confirm that power is off when I have already switched it off at the main isolator/switch and (2) that there is a live again after reconnecting (if there should be one). Time to find another method, I think!

 

[davelx]

This is the correct type of tester for the job:

http://isswww.co.uk/VoltageContinui...e-VI13700G-Voltage-Indicator/?source=googleps

Don't forget correct isolation procedure.... in a nutshell:

(a) Check the tester on a known live source to a known good earth

(b) Check the circuit you are working on - check between both live (line and neutral) conductors and a known good earth (why check the neutral - in case there is another circuit borrowing it that you have not turned off! In that case, checking between line and neutral would give you a false dead reading. Very common in older properties.)

(c) Check the tester as in (a) again. Why? you ask. Because it just might have failed between (a) and (b).

 

[daverk]

Many thanks to all of you who have responded to this. I'm going to give up on the neon screwdriver because there is a risk that it can give a misleading indication - and I'll try one of those Martindale Voltage Indicators.

 

[Taylortwocities]

Many thanks to all of you who have responded to this. I'm going to give up on the neon screwdriver because there is a risk that it can give a misleading indication - and I'll try one of those Martindale Voltage Indicators.