Why do I need anything more than a Neon?

[Pete E]

Looking for a little help from members here...

First I should say I am not a Spark, but have a telecoms back ground and I was taught a little about electrics during my apprenticeship along time ago.

I am looking for a reliable of testing domestic circuits are dead before doing any work on them. This work would be fairly low level DIY stuff such as changed sockets or fittings ect, nothing too complicated.

I have but don't like/trust neons, and I also aware the DMM's are not the best tool for what I want...I was considering a volt stick, but it seems they are not fool proof either?

Can anybody recommend a relatively cheap voltage tester suitable for home and DIY use?

Some may think I am being ----, but in previous house ( a semi detached cottage) I had a situation where a neon and a DMM was picking up a 110V voltage on a supposedly isolated lighting circuit.

I assume I am going to need to go for a specialist voltage tester/probe? If so is there any people can recommend at a reasonable cost?

Thanks in advance,

Peter

 

[SparkyChick]

Hi Peter,

Pick yourself up an approved voltage indicator... something like a Fluke T-90 which you can get from the forum sponsor test-meter.co.uk for around £39+VAT.

The reason things like neons and DMMs pick up voltages that are not there is down to their input impedance. They generall have high impedances resulting in a very low current flow. Voltages induced in the cable by induction or capacitive coupling will be detected by them. AVIs have a much lower input impedance and as such, allow a larger current to flow thus dissipating such phantom voltages as there is not enough charge to maintain them once a significant current is allowed to flow. I'm sure the terminology is a little off, but that's the general principle and the reason why AVIs are the preferred method.

 

[telectrix]

here from forum sponsor. several others for various prices, but a cheapish one is all you need. a proving unit to go with it is advised.

Fluke T90 Voltage and Continuity Tester - https://www.test-meter.co.uk/fluke-t90-voltage-continuity-tester/

 

[telectrix]

beaten by a woman. and i'm not even into S&M.

 

[Spoon]

beaten by a woman. and i'm not even into S&M.

I bet you have a room dedicated to it mate..

 

[Pete E]

Hi Peter,

Pick yourself up an approved voltage indicator... something like a Fluke T-90 which you can get from the forum sponsor test-meter.co.uk for around £39+VAT.

The reason things like neons and DMMs pick up voltages that are not there is down to their input impedance. They generall have high impedances resulting in a very low current flow. Voltages induced in the cable by induction or capacitive coupling will be detected by them. AVIs have a much lower input impedance and as such, allow a larger current to flow thus dissipating such phantom voltages as there is not enough charge to maintain them once a significant current is allowed to flow. I'm sure the terminology is a little off, but that's the general principle and the reason why AVIs are the preferred method.

Thanks for that...I assumed the 110V was down to some sort of induction issue, and funnily enough as you suspected, when I tested it with an old analogue multimeter, it didn't register the voltage, but not being 100% sure, I was not taking any risks.

The thing that confused me was that the bulbs in the cottage seemed to blow a bit too often and rarely last more than three or four months.

After finding the stray voltage I did call out two Sparkes but neither seemed to be able to get to the bottom of it although both said it was nothing to worry about...

 

[HandySparks]

Hi Peter,

Pick yourself up an approved voltage indicator... something like a Fluke T-90 which you can get from the forum sponsor test-meter.co.uk for around £39+VAT.

The reason things like neons and DMMs pick up voltages that are not there is down to their input impedance. They generall have high impedances resulting in a very low current flow. ...

Really need to go up to the T110 to allow elimination of 'ghost' voltages. It has switchable input impedance by pressing a switch on each probe. Drops input impedance from 200k to 7k.

Fluke T110 Voltage/Continuity Tester - https://www.test-meter.co.uk/fluke-t110-voltage-continuity-tester/

 

[robd]

Kewtech kt 1780 is a nice little tester and what I have in my tool bag after years of fluke I'd say I prefer it. Pick on up for £30-40 usually. Does voltage continuity and unlike some Ive had measure live to earth directly without tripping an rcd

 

[Pete999]

Looking for a little help from members here...

First I should say I am not a Spark, but have a telecoms back ground and I was taught a little about electrics during my apprenticeship along time ago.

I am looking for a reliable of testing domestic circuits are dead before doing any work on them. This work would be fairly low level DIY stuff such as changed sockets or fittings ect, nothing too complicated.

I have but don't like/trust neons, and I also aware the DMM's are not the best tool for what I want...I was considering a volt stick, but it seems they are not fool proof either?

Can anybody recommend a relatively cheap voltage tester suitable for home and DIY use?

Some may think I am being ----, but in previous house ( a semi detached cottage) I had a situation where a neon and a DMM was picking up a 110V voltage on a supposedly isolated lighting circuit.

I assume I am going to need to go for a specialist voltage tester/probe? If so is there any people can recommend at a reasonable cost?

Thanks in advance,

Peter

 

[Raeb]

Apprentices used to hate me when i took the neon and resistor out of their shiny new test screwdriver.
The video makes me happy i never trusted a neon screwdriver.

 

[Andy-1960]

We should all start a campaign to get neon screwdrivers and the like banned. They are nothing short of dangerous.
The thing is they not only show up phantom voltages as explained by Sparkychick, but more worryingly they can also fail illluminate when the circuit is actually live if the user is well insulated from ground.

 

[robd]

Great video by the way

 

[static zap]

........ all start a campaign to get neon screwdrivers and the like banned. They are nothing short of dangerous........

They are so Carp on a bright sunny day ...
(less of a problem in the UK at moment)
(For the younger generation Killer ... means death in "our speak")

 

[PEG]

Excellent post Sparkychick- i would always recommend anybody,even a DIYer,to get an approved AVI. They are too useful,and,too cheap to worry about,not to.

I bet i have just put the value of a good AVI,in my food recycling bin.

I can guarantee,that yet another AVI,would have benefited me more,than my own weight in avocados......

 

[SparkyChick]

Kewtech kt 1780 is a nice little tester and what I have in my tool bag after years of fluke I'd say I prefer it. Pick on up for £30-40 usually. Does voltage continuity and unlike some Ive had measure live to earth directly without tripping an rcd

That's where the buttons on the T110 and T150 come into play... With them not depressed, the current draw is quite small, certainly not enough to trip an RCD. Pressing the two load buttons causes around 30mA to flow @ 230v allowing you to trip an RCD on demand... handy if you're struggling to identify a circuit in an unlabelled board.

They are also pretty handy things to have if you do any work on say switch mode power supplies which often have quite sizeable capacitors charged at mains voltage.... stick the T150 across the cap and press the buttons... nice controlled discharge. Do that on all the big caps and you can safely handle the board without a big zap.

Edit:- Just to qualify that last statement... assuming you're not daft enough to still have the board powered up