I have a number of lamps where I work that can be dimmed to three levels and turned off by touching the metal frame. I discovered today that the frames have anywhere from 48 – 53v on them. (This is a 120v lamp.) I guess this 53v is a function of how the lamp turns off and on by touch. I know this is considered low voltage, but it just doesn’t seem right to me that this much voltage is meant for human contact. Especially since the lamps are located two feet from metal wall heaters. The lamp does not have a ground wire and of course the heater is grounded, so all it needs is a finger on each for the 53v to go to ground. Is this safe?
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how did you measure the voltage??
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'Wer ist jetzt der Idiot?'
I measured the voltage with a fluke meter, one lead on the ungrounded lamp frame and one lead on the neareby grounded wall heater.
"I measured the voltage with a fluke meter"Fluke is a brand name, not a type of meter. My guess is that you used a high impedence digital voltmete.They are so "sensitive" that will measure capacitively couple signals from other circuits.Open circuits will often measure 20 - 100 volts on them when a digital voltmeter is used.If you have a real concern then there are a couple of things that you can try.One is to put the meter on a current range and connect from the frame to ground and see if you get any measurable current.Personally I would "ground" the lamp through a 100k resistor and then make the voltage measurement. But I doubt that you have one handy.Another option would be to plug it into a GFCI protected receptacle. Then ground the case and see if the GFCI trips.
Or just stick your tongue on it.
I don't think you have a problem, I checked some of my table lamps just now...they have the same touch feature....
and I was reading about 2.3 volts.
Flukes are very sensitive and will display all sorts of volts, both true and capacitive , which can make you nuts if you let it...for peace of mind try what BHartmann has suggested, & use a large load (resistor) to verify your readings...or just get someone else to turn the thing on.also, as a rule I try not to touch electrical apparati and grounded surfaces at the same time, but that's due to constant reminders and some hard lessons learned during my apprenticeship, and I offer that as a VERY good idea..
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'Wer ist jetzt der Idiot?'
It ain't the voltage that kills you, its the current. You can go touch a Van de Graff generator and get several hundred thousand volts but the current is in nanoamps, so its harmless. The voltage on the touch lamp serves as a trigger to change the light setting. When you touch it, it changes the voltage, changing the lamp setting. As long as the touch voltage is supplied through a high impedance, it can't do any damage to you.
Erich
The Force will get you every time.
Ever try working a touch lamp with your tongue?
MarkH Wrote: "Ever try working a touch lamp with your tongue?"Yes, works just as well. Should work just as well with ANY body part :-}
I haven't tried working one with anything but my finger, but yes any body part should work fine. I thought they worked by capacitively coupling 60 hz to a detector circuit, so there should be no actual voltage present on the lamp frame. Probably just a fluke.