How Does a neon screwdriver work?

[bernardgreen]

though I am slightly worried about Bernard Greens' thoughts;

Could you explain which part of my thoughts gives you cause to worry.

 

[riveralt]

The instruction book advises the user that putting it near a socket is a reliable indicator of whether said socket is live or not.

Can you not see what rubbish this statement is - isn't it completely and blatently obvious. Perhaps in your case clearly not.

Riveralt. But my dear fellow I wasn't testing whether the cable was live or not, as I had planned to remove it under isolated conditions regardless. I was testing the screwdriver. I apologize if this was not completely and blatently obvious.

So you leave a live cable (cut ends) (or were you not aware it was live) in the void above your bathroom ceiling - nice one
Then ......

I used one to 'check' some 1.5mm T+E wires in the void above the bathroom ceiling........lit up when I put it near the cut ends.

and if it hadn't lit up - would you be communicating with us now???

 

[david911cockburn]

Firstly Bernard,
Your reply is a little vague, please give us some examples of capacitive elements that the we 'must' be in contact with.
Please remember that you are putting forward theoretical ideas on a subject where others are talking from first hand experience, it would be easy for you to end up looking as if you are speaking through the seat of your trousers!

Secondly,
Wherever you come across strange and seemingly unexplainable occurances like a cable that turns out to be disconnected at both ends having appeared to be 'live' when you tested it, the best place to find for an explanation is by looking at the 'people' that you are working with or who have access to the site, a forman dropping in un-announced for example having a bit of a jape perhaps.

 

[cajar]

Riveralt, you are plainly at or beyond the limits of your comprehension. No cables were left live (miss the point much?) and the screwdriver was being tested by me (to see if the tester could correctly identify what I knew to be true) while following my normal course of safe action.

David, I can discount third party interference quite easily, given the only people in my home at that time were my wife and I. The dog's sense of humour does not extend to creating false positives on mains cables. I conclude the tester is worse than useless.

 

[cajar]

double post

 

[ban-all-sheds]

NOTE TO ALL:

This is a warning we should all take very seriously, as it comes from someone who is an acknowledged expert in the matter.

it would be easy for you to end up looking as if you are speaking through the seat of your trousers!

 

[sparkticus]

Cockburn all you are doing is confirming that you are an idiot.

What would it take for you to just to go away?

 

[bernardgreen]

please give us some examples of capacitive elements that the we 'must' be in contact with.

Take any two items that are electrically conductive. Even if they are several feet apart from each other they form a capacitor. Changing the voltage on one will affect the voltage on the other. Most people see capacitors as components in electronic equipment.

The human body forms a capacitor with the earth. and with all other conductive items.

Please remember that you are putting forward theoretical ideas on a subject where others are talking from first hand experience,

I believe my 40 year career in electronics design, factory automation system design, telephone exchange equipment design and safety critical monitoring systems has provided me with a considerable amount of first thand experience. I have also been involved in post incident analysis of failure modes of equipment.

it would be easy for you to end up looking as if you are speaking through the seat of your trousers!

I doubt that would happen.

I agree with some of the controversial opinions you hold.

Earthing and bonding have developed out of a series of compromises between cost and hazard reduction and that compromise is not a fit for all application compromise.

However even after 40 years of sucessful career I am still open to learning.

 

[sparkticus]

I believe my 40 year career in electronics design, factory automation system design, telephone exchange equipment design and safety critical monitoring systems has provided me with a considerable amount of first thand experience. I have also been involved in post incident analysis of failure modes of equipment.

Sir Cockburn, do you have anything even remotely close to such experience?

 

[Alarm]

Example of a neon test driver.

House rewired, certs issued.
East European ( but could have been anyone) comes to do Gas meter swap. Says gas pipes are live. Refuses to swap.
We go back and test all okay.
Meter man comes back and says "Gas pipes are live".
We go back and check again, dunno why TBH. Ask the owner how was it tested, he said the man had a glowing screwdriver, my mate and me started to laugh.
I had one in the van somewhere as it had not been THROW AWAY for some reason. I shuffled up the hall and it lit up, so the carpet must be live too!
Then I rubbed it on my arm and guess what, yep I`m Captain Electricity

We phoned the gas board and asked what qualifications the man had to condem a installation, she said he had done a 3 day course. After much merriment we got her to agree for another engineer with correct test equipment to meet us and guess what, all was safe.

Never charged the client, done loads over the yrs for him. And was on way home.

Moral of this, Neons are fit for bin not purpose.

 

[riveralt]

Riveralt, you are plainly at or beyond the limits of your comprehension. No cables were left live (miss the point much?) and the screwdriver was being tested by me (to see if the tester could correctly identify what I knew to be true) while following my normal course of safe action.

I am terribly sorry if I misunderstood you, I simply read the words that you wrote ...

I used one to 'check' some 1.5mm T+E wires in the void above the bathroom ceiling........lit up when I put it near the cut ends. So I isolated the power at the CU, and traced the wires back - completely unconnected to anything and just pulled away in my hand.

None of which says anything about you knowing that the circuit was live nor that you were conducting an experiment on this useless piece of junk.
Indeed all your statement seemed to indicate was that you had tested the neon screwdriver and concluded it worked.

So please don't hold me responsible for your inability to communicate in a manner which properly explains what you think you were trying to do.
I mean, why go to the extent of accessing a void in a ceiling bathroom to find a live (one assumes) unguarded circuit just to test a neon screwdriver. What would you have done if the neon didn't light up?

My criticism of you, apart from your inability to properly communicate, is that you openly admitted conducting a stupid experiment on a useless piece of junk without highlighting the importance of utilising the safe isolation procedure until prompted by myself.

David, I can discount third party interference quite easily, given the only people in my home at that time were my wife and I. The dog's sense of humour does not extend to creating false positives on mains cables. I conclude the tester is worse than useless.

As for your decision to communicate with Mr David Cockburn noted author, self publicitist and expert on ....well ....... erm!!...... nothing really

 

[Wontdothatagain]

A practical demonstration, 1000V gloves on, neon is on the Live terminal of a meter on my bench. You can just make out the glow of the Neon.

Untitled

• Wontdothatagain
• 29 Jul 2011
• 1

We use these when installing meters as they are deemed the only instrument to prove polarity. We also use them to check all extraneous conductive parts and conductive parts are not live before we touch anything but after this we then use a test lamp to double check.

 

[Alarm]

You can just make out the glow of the Neon

Kewl, so with a bit of extra light about. Eyesight fading slightly ( dont deny it once past 40 its downhill, even if you think it aint).

You trust it.

Really.....................So why the nice gloves ?
Bet the shoes are rubber soled too. ( Not takin the pee here, but JP might wonder).

 

[ban-all-sheds]

they are deemed the only instrument to prove polarity.

We also use them to check all extraneous conductive parts and conductive parts are not live before we touch anything

but after this we then use a test lamp to double check.

Why? Don't you trust the trusty neon screwdriver?

 

[sparkticus]

Don't you trust the trusty neon screwdriver?

I trust the trusty neon is not trustworthy therefore they have no trust in the trusty neon and trust something else after not trusting the trusty neon

But you have got to wonder why they support its use in the first place if its indications need to be checked by another instrument.