I use non contact voltage tester function of Uni-t ut210e for detecting main wires under/in walls. It worked pretty well until yesterday.

The wall is made of bricks/mortar and some metal profiles (as I experienced today when drilling holes for wall shelf). There is 0 voltage between that metal profile and the ground.

Also, there is a wall socket 20 cm from the bottom of the wall. Mains voltage is 230 V.

What could be the cause of NCV meter beeping over almost entire wall?

  • 1
    there's a lot of reasons, but mostly water or metal in the wall inducting emi from the air and false triggering. it's nothing to worry about; my nose often makes it beep.
    – dandavis
    Nov 9, 2017 at 5:35
  • well, it's very strange - my nose doesn't make it beep, but my brain does (only if I'm sharing the meter in hands)
    – Qeeet
    Nov 9, 2017 at 11:04

1 Answer 1


When the batteries start to run down this can cause the filters not to work which can result in erratic sounding. Also the electronics also go bad. this can cause erratic sounding. They are mass produced and don't always have a long life.

  • tried with new fresh batteries, result is the same. Meter I got is fairly new (2 month), I used it rarely.
    – Qeeet
    Nov 9, 2017 at 11:01

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