Fluke 1AC Tester

Hi All,

I bought a Fluke 1AC tester as I will be changing some lights in my garage soon and I wanted to ensure, in addition to turning the power off, that there will be no electricity running.

When I bought it I touched the tip against a table lamp which has a metal base and it beeped and went solid red. Now if this is indicating that the base is live why don't I get a shock if I touch it and, secondly, is it live and is it dangerous?

I'm not a qualified electrician and I only undertake electrical jobs such as changing a light fitting if I am just swapping over like for like.

However, I'm concerned with the response I got from the lamp as I would just assume, if I didn't know better, that it is live and would steer clear.

Appreciate your thoughts - thanks.

These thing are, as you have discovered, unreliable.

You need a two pole tester. A cheap multimeter will do.

EFLImpudence said:

These thing are, as you have discovered, unreliable.

You need a two pole tester. A cheap multimeter will do.

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Thanks for your reply. That's quite worrying when dealing with something that could kill you!!

Any recommendation for a multimeter?

I don't know to actually recommend any cheap ones. Perhaps someone else does.
Just something like this:
http://www.maplin.co.uk/p/mini-digital-multimeter-with-voltage-detector-n61lk



Mine is probably to expensive for you but it's really good.
http://www.maplin.co.uk/p/fluke-117-true-rms-multimeter-r43bt

Thanks - appreciate the links.

The type you have would cost me more than the lights!! Mind you if it saved my life it would be worth it, although some may disagree

When you get one:

On 500/600V~ (AC) setting, place red probe on the lamp body and black probe on a known earth - socket screw or an appliance carcass, hob, oven etc.
There should be 0V or perhaps 1 or 2.

Also, with same probe placings set meter to low Ω (ohms).
It should read very low - just 0, 1 or 2Ω.

The Fluke 1AC voltstick is one of the better ones, and they definitely have their uses - proving for dead is not one of them.

The reason it detected voltage on the base of your metal lamp is likely just because the cables run close to the surface of the lamp. You don't need to be in direct contact with a cable for it to tell you if it's live or not.

Iggifer said:

The Fluke 1AC voltstick is one of the better ones, and they definitely have their uses - proving for dead is not one of them.

The reason it detected voltage on the base of your metal lamp is likely just because the cables run close to the surface of the lamp. You don't need to be in direct contact with a cable for it to tell you if it's live or not.

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Thanks for explaining. So, in this example if someone totally unfamiliar with the lamp having never seen or touched it before was to get the reading that I did would they assume the base is live?

Well, that would depend on their level of experience I guess. But the casing won't be live, you'd have found out before now!

To show what I mean, hold the 1AC near to a TV flex or something, and see how far away from it, it lights up.

Or rub it on your knickers, it will light up then and there's no mains voltage anywhere nearby (that depends on the knickers i suppose )

Taylortwocities said:

Or rub it on your knickers, it will light up then and there's no mains voltage anywhere nearby (that depends on the knickers i suppose )

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Wouldn't work on mine! Not that they're knickers.....got some snickers, they might work

There are at least three models with different voltage ranges 20 V to 90 V AC, 90 V to 1000 V AC or 200 V to 1000 V AC. They will work with static electricity I would rub on jumper to test it was working. They are a good second test for dead. We would test with a two probe tester, and then test the tester in a proving unit but things like borrowed neutrals can still be missed. So the tester you have or the neon screwdriver will it is hoped alert one if the neutral is missing or borrowed. Always nice to have a second string to your bow.

However non of the testers are any good if you don't know how to use them. Plug in testers like this one are very good as they come with an easy to read instruction set and you can't really put any switch in the wrong position and do any harm using it. The simple clamp on meter or voltage tester normally have no short circuit selection so you can't in error leave it on the wrong range and as a result hurt yourself. Most cheap meters don't have leads to the quality required for mains work, there should be a protector so your fingers can't slip down the leads, only 1 mm of metal showing so a real pain to use, and a fuse built into the leads.

When my son started to get interested I allowed him to use my AVO Mk8 because it had built in safety cut out as well as built in fuses. If with the cheaper meters you in error have them set to amps rather than volts there can be a big bang and a lot of damage. With some this can also happen set to ohms. In a class of 20 "A" level students 10 of them managed to blow the fuses in the multi-meters. I blame the lecturer but the point is it is easy to make the mistake even advanced level students made the error. I would hope electricians are better taught the error with 12 volt was not so bad, with 230 volt it is a lot worse.

BF said:

Now if this is indicating that the base is live why don't I get a shock if I touch it and, secondly, is it live and is it dangerous?

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To get a shock there has to be two points of contact with the body and with a potential difference between them. ( voltage ) You can ( but do not try it ) hold a live wire without getting a shock provided no part of your body is in contact with any other metal that is at earth or Neutral ( or any other potential different from Live ) and you are standing on a dry non conducting surface such as carpet.

Birds can perch on over wires at 11,000 volts without harm because there is no contact with any other conducting surface.

The lamp case may be at 120 volts ( mid point between 0 and 240 ) due to capacitive coupling from the wires inside to the metal case.

The reason trusting those items is dangerous is that they do not detect Live wire, they indicate a potential difference between the person holding it and the metal it is touching.
If the person is standing close to a light switch they will, by capacitive coupling from the Live wires to the switch to their body, be at a potential above 0 volts maybe as high a 230 volts. ( capacitive coupling is not able to pass any significant current so this is a perfectly safe condition ) Hence when this person holds the tester to an earthed item the potential difference betwen their body and the eathed item will cause the tester to indicate "potential difference". The danger in this situation is that when touching a Live wire there is no difference between the potential of the person holding the tester and the Live wire so it will NOT indicate that the wire is Live