What am I measuring if I set my multimeter to AC voltage readings and take the black probe out of COM? It seems that I am getting higher readings when I go near a light or my computer screen. This measurement seems to get more sensitive (I think) when I make a circular loop with an ordinary copper wire and connect the red probe with the loop.

What am I measuring in the two cases? Are they measuring the same thing?

  • $\begingroup$ Not sure what you are measuring. Follow the instructions for the meter and use both leads. $\endgroup$
    – Solar Mike
    Nov 22 '20 at 7:24

You are measuring the electric field in the air. Your multimeter has a very high input impedance - typically 10 MΩ. If you connect a low resistance - even 1 kΩ - between the V and COM inputs you will find that the reading collapses.


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