I was trying to check and see if a cable was bad to something not working when I noticed my non-branded cheap daylight bulb/ UV lamp was giving off a very bright reading from over 2 feet away and overtaking everything on the desk.

I had to unplug everything in the area to make sure that's what the detector was picking up. I know my small non-contact detector works great, and doesn't pick up anything that strongly or far away I've tried searching google and whatnot but could not find anything to do with this sort of thing

  • My question is could the wiring be bad on the inside, like exposed, even though it's working fine or is this a common thing with a strong daylight lamp?
  • Is it dangerous for someone to sit next to if a detector is reading it from far away?

1 Answer 1


What you're seeing is quite normal for metal fixtures supplied with a non-grounded wiring method. And especially so if the wire connected to the screw shell of the lamp socket is the "hot" wire instead of the "neutral" wire as it should be. Is your fixture metal? Does it have a 3-prong plug on the cord? If only 2 prongs, are they polarized (i.e. one blade wide and one narrow)? Same questions apply to the receptacle the plug goes into. And finally, what sort of wiring supplies that receptacle? So no firm answer is possible until all those things are investigated. ADDENDUM: If your fixture uses some sort of fluorescent lamp, that could also be the cause, as those devices work by generating relatively intense electromagnetic fields, which is what the non-contact voltage detectors actually detect.

  • Thanks for responding :) The fixture itself has a plastic shell all around it, it's an adjustable neck so probably some sort of metal. The base of the lamp says its 120 V and 68 hz. It's 2 prongs and they are polarized. It's connected to a surge protector, which is connected to a (probably ungrounded) 3 prong outlet. I tried checking other things plugged into the same surge protector, I brought in another kind of lamp, nothing lights up the non-contact voltage detector from that far away or makes it light up super bright.
    – MelC
    Jan 31, 2023 at 4:45
  • Seems like this is more "questions for OP" than "answer". Maybe it should have been better off as comments...
    – FreeMan
    Jan 31, 2023 at 14:16
  • @MelC Added a remark re fluorescent bulb.
    – kreemoweet
    Mar 2, 2023 at 9:40

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