neon screwdriver test

[Acchillo]

No point in saying neon screwdrivers are not to be used. But can you pls point me to a good doc explaining how to identify live cables (and some theory if possible?

The multimeter I used measures the amplitude of the AC, but does not identify which cable is live. it is a digital tester, Are analogue testers better in this situation? why?

I also bought a Fluke T50UK voltage/continuity tester to identify live cables. It does the job, but it trips the RCD in the CU too often for my taste. Do I do anything wrong?

THX

 

[Albert]

I agree, to be sure you need a veryfied meter.

It is possible that yout T50 tests other things at the same time as measuring voltage, probabely one of this tests effectes the balance between L & N and this will trip the RCD, I would think that any tester that will measure voltage only will allow you to get a reading without the RCD tripping.

You can identify a live wire by it's colour, how it is connected and of coure this must be veryfied by measuring it.
A voltage reading will show if you measure between L & E and L & N, but N & E will show a very low reading or nothing, so the wire that reads a voltage to earth is the live one.

You have to be very carefull and verfy every wire even it does not make sense that it can be live, you never know who was the last one to do the work and what methods he used.

I am using, as my basic tester the Fluke T5-1000, the advantage is that every test has to be pre-selected so it does only one test at a time, adding to this it has an integrated clamp meter that can read the current in a wire without disconnecting it.

 

[RF Lighting]

The multimeter I used measures the amplitude of the AC, but does not identify which cable is live.

If your tester display says something roughly between 230-250v then the cable is 'live'. If the tester says something roughly between 0-20v then the cable is not 'live'.

I use Fluke T5-1000 test probes and have never tripped an RCD when testing for voltage or continuity, so yes I thing you are probably doing something wrong. How do you carry out this test? Which conductors do you test between?

 

[Acchillo]

Thanks for the help.

Life is always more complex that this.

I guess a meter can show 0-20V when measuring voltage either between two live wires or between two non live wires.

Can anyone point to any white paper explaining all measures that can be done to identify live wires with testers or voltage continuity meters?

I would like to understand why the fluke trips the RCD? and How I can be absolutely certain a cable is non live (I believe a 0-20V tester measure is not conclusive enough...) .

 

[securespark]

The best test for a neon driver is the impact test, as follows:

Place driver on hard floor.

Jump up and down on it several times.

Place pieces in bin.

Do not replace.

Buy decent test equipment.

 

[Acchillo]

Thank you for the speech on how to destroy the neon screwdriver. I was a 35 email thread launched some months ago where everyone rambles on destroying the neon screwdriver. Point WELL TAKEN!

My question is another one: can you pleas tell me the best way to test a live connection. Can you please read the email thread with the question.

 

[Steve]

best way to test a live connection - hold the multimeter probes between live and neutral, or between live and a known good earth.

Make sure the multimeter is set to the right setting and range, or it will smell funny and possibly catch fire.

 

[Adam_151]

The best test for a neon driver is the impact test, as follows:

Place driver on hard floor.

Jump up and down on it several times.

Place pieces in bin.

Do not replace.

Buy decent test equipment.

Lol SS... but may I suggest a wiser approach would be to understand the limitations of whatever you are using, personally I find a neon screwdriver is usful for working out whats what in a complicated lighting arrangement (which switched live is which), if for example its a mess of loose choc blocks in an enclosure, not having to try and get a good contact on two terminals simutaniously is sometimes useful...

 

[Steve]

not having to try and get a good contact on two terminals simutaniously is sometimes useful...

yeah, and tilting your head upside down while maintaining contact, then trying to remember the reading, all the time remembering not to let one's hands go any nearer to the cable or else risking death

 

[johnny_t]

The key is to know where your reference is - You should be able to identify an earth wire or connection reasonably easily, so you need to measure between that Earth and whatever wire you are questioning.

Have you got a specific example that you need to test ?

 

[Albert]

not having to try and get a good contact on two terminals simutaniously is sometimes useful...

yeah, and tilting your head upside down while maintaining contact, then trying to remember the reading, all the time remembering not to let one's hands go any nearer to the cable or else risking death

And as you are on the ladder, holding dodgy probs to dodgy connections, you need a good scratch somewhere...

 

[Acchillo]

The problem is, as someone said, to identify a good earth point with confidence and in places where this cannot be extracted from the wiring.

As an example, I am now trying to dentify live cables inside a messy connector box in the garden. As there are other boxes buried somewhere between the controlling switches and this box, I find it hard to track down the entire installation. The only certain thing is that the earth has not been properly extended to that garden box.

What external reference should I use to measure all cables in that box and identify the live ones? Note that in this case relative (i.e. between wires in the box) voltage measurement does not work as a low Voltage measurement can show up between two live wires.

P.S. Please stop the rambling about neone screwdrivers in this email thread. The topic has been extensively debated in other threads.

 

[farndon]

I use a digital multimeter between earth and the other conductors to find the live

 

[Acchillo]

Thanks Farndon,

And where would you get the earth assuming there are no wires closeby that can be deemed to be at the same potential as the earth?

Do I have to get an extension from a well-know earth connection (i.e. from a socket inside the house (impractical!) or can I use something else? and what?

Claudio

 

[cozycats]

From you've said about other buried connection points RIP IT OUT and start again! It's the only really safe thing to do!