Mastercraft Non-Contact Voltage Tester

Many reviewers thought this is an issue, when in fact it is a quality: it detects static electricity! Try rubbing it off your synthetic fibre shirt, or your hair. This is why it may beep on items that you would expect are not having a charge. Try touching that item with your hand (to allow electricity go through your body into the ground) and then test again - now zero beeps. The tool is very useful exaclty for this reason, that it shows any form of electricity. It detects if a light switch is on or off just by holding it next to the switch button. Hold it next to a cable, it will tell you if that cable is plugged into power or not. This is very useful when you cannot reach the plug but have acceas to a cable connected into that plug. The frequence of beeps INCREASES with the voltage, so a low voltage USB port will beep less frequently than your 110V power plug. I suppose they did not put an on/off switch ON PURPOSE, so no one will sue them because they were dumb enough to forget turning on the tool before measuring... This way it is always-on. Totally recommend it, been having it for 5 yrs and works as a charm every time (well, there are no moving parts so what can go wrong?).

Mine works well, but there's no way to turn it off other than removing the batteries, which is very difficult to do in the field. This almost guarantees that the next time I go to use it, it's dead.

The cap is broken when installing the battery as it is very difficult to remove it. Latter, my battery is a little bit leaking, after I cleaned the battery contact surface and installed the new battery, it does not work at all. When using it to detect the voltage, sometimes it does not work: there is voltage while this tester failed to detect it. This could cause safety issue

Was hoping the other poor reviews were wrong. Nope. It beeps when it contacts anything pretty much. I can’t believe it wasn’t discontinued sooner.

I just simply wouldn't trust this tool for determining if a circuit is energized. It tones to the touch of almost anything that is not energized including fingers and switch boxes.