OT what is that vibrating sensation you get when you lightly touch the metal on a mains appliance?

I've long wondered this but have never had a knowledgeable bunch of people sitting there with idle time just waiting to jump up and offer me an explanation... ;-)
What is that vibrating sensation you get when you lightly touch the metal on a mains appliance?
What causes it? Is it a sign of inadequate earthing?
--
dave @ stejonda

"To materialist eyes, India is a developing country;
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Get your wife a cordless vibrator, it'll solve the problem. Alternatively, lower the light switch to buttock height and get her to turn the lights on with her cheeks, you'll then have a happy wife and no need to worry about vibrating switches.
Rgds
Andy R
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That and a current leakage through the insulation in the appliance ...
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Hmmm, - okie thanks - is it dangerous?
--
dave @ stejonda

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On Tue, 18 May 2004 18:06:22 +0100, in uk.d-i-y "dave @ stejonda"

Yes, I would get that looked at. There's the dodgy earthing, inadequate circuit protection and the source of the leakage to find!
--

SJW
A.C.S. Ltd.
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eeek - a job starting tomorrow - you're really suggesting that an RCD (or whatever it is) in the CU should've been tripping then...
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dave @ stejonda

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On Tue, 18 May 2004 19:30:52 +0100, in uk.d-i-y "dave @ stejonda"

Well, I thought that after I posted, possibly not. But it wants checking to make sure it is functioning correctly. It depends what the leakage on the appliance is, you could measure it with a meter to check it against the RCD In rating.
--

SJW
A.C.S. Ltd.
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In general, no. Unless it happens to be fatal. It should be at least investigated. Do you own a multimeter, and what is the appliance?
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We used to have an electric kettle - back in the sixties and it ws second hand even then - which we knew was switched on because it gave us a buzz if it was.
We also had one of those electric one bar fires, with the curved back, which received the Home Service.
No, straight ...
Mary
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On Tue, 18 May 2004 22:44:53 +0100, "Mary Fisher"

You're thinking of when the Home Service was called 2LO, Mary.
.andy
To email, substitute .nospam with .gl
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wrote:

if
which
It was never called that. 2LO was the service before it was divided into regions.
Mary

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LO standing for London, the ident of the actual transmitter.
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*Why don't you ever see the headline "Psychic Wins Lottery"?

Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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o_O
Yup - a rather elderly(!) Skywood Model 500 (as advertised in Practical Wireless in the 60's and possibly earlier)

The one I keep resting my arm gently against is a floor-standing lamp which has metal tubing as the upright. But I've also had the effect from the metal fascia of a Technics hi-fi amp.
--
dave @ stejonda

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...snipped

As others have, said it's leakage current; what you're feeling is mild nerve stimulation as you form a path to earth. The cause is almost certainly capacitive coupling to an ungrounded conductor. If the equipment is double insulated it's absolutely normal to get this effect, if it's not double insulated (i.e. it's supposed to have a ground wire) then check the earthing and treat it with care.
Dave S
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writes

Ok, that's the explanation then - thanks all.
--
dave @ stejonda

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New meters (digital) are only around a fiver, but if not abused, it should be fine.

If it's two appliances, it's less likely to be a fault with the appliance. As a basic check, take the plug out, and measure on a low-ohms range the resistance between the earth pin (the long one) and the metal of the appliance. It should measure under an ohm or two.
If this is so, then it's likely that the appliance is not at fault.
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It works fine - except that the high Ohms range doesn't work any more since the 15V battery it requires is no longer available. I still find it more satisfying to see a swinging needle rather just an LCD readout. :)
--
dave @ stejonda

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Check out Ebay for a spare battery. What type is it?

Trouble is most measurements given these days assume a high impedance meter, so you might have a problem there.
DVMs are now available with a bar graph extra readout which gives some semblance of a swinging needle.
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Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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BLR154
Well high impedances were always claimed - but I technology might've moved on a little since I bought this for 10/6.

Mostly it only gets used for continuity testing nowadays but I'm getting tempted to take a look.
--
dave @ stejonda

"To materialist eyes, India is a developing country;
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Thought I could lay my hands on an old list, but can't. However, if it's the same as an AVO model 8, these batteries come up on ebay.

Just a bit - most cheap meters these days are near enough the equal of a valve voltmeter of old. About 10 Meg input.

Most DVMs have a proper continuity tester with a buzzer that sounds below a preset resistance.
--
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Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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