Getting Small Shock From Household Electronics Cases (in Asia). Why? - Electrical - Page 2 - DIY Chatroom Home Improvement Forum

 DIY Chatroom Home Improvement Forum Getting small shock from household electronics cases (in Asia). Why?
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11-11-2009, 09:41 AM   #16
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>>see below
Quote:
 Originally Posted by scootley I connected one end of a wire to a water supply pipe. I connected the other end to one terminal of a small light bulb rated that said "12V 5W" on it. >>So the hot resistance of this lamp is (12^2)/5 = 29 ohms, and the cold resistance is 10x or 15x lower. It takes 400 mA to light. The light does not illuminate. >>So the current is less than 400 mA. With the light connected, I measured the AC voltage between the 2 terminals of the light, which reads 0V. >>see below Is this the measurement you were talking about? >>Yes
With a cold resistance of 3 ohms or less, and a shock current of ~1 mA you'd see 3 mV across this 12v bulb.

I would try a 120v incand.lamp of low wattage. The filament has a higher resistance.

Better yet, substitute a 1k, 1/4w or larger resistor for your body. If you read 1vac you've got your 1 mA shock current. If you read 10vac you've got 10 mA through this low value resistor.
Most people with a large contact area and dry skin will have a resistance of 1k to 6k.
http://bme.ccny.cuny.edu/faculty/mbi...tageReview.pdf

11-11-2009, 10:09 PM   #17
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Quote:
 Originally Posted by scootley I With the light connected, I measured the AC voltage between the 2 terminals of the light, which reads 0V. Is this the measurement you were talking about?
Yes. As you observed, connecting the light "drained" to ground the current that was giving shocks, and that current was very small given that the light did not come on. I would consider it safe to ground the equipment to a known ground (attach the wire directly, no light connected in between) and not worry about it any more.

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Last edited by AllanJ; 11-11-2009 at 10:12 PM.

 Tags enclosure , ground , polarized , shock

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