A while ago, I hammered some nails into a wall trough which wires are running (taking care not to hit any wire).
But when I use a multimeter to measure the voltage between the nail and some other point of the wall I get a reading of 0.89 Volts. When turning the fuse off I only get a reading of 0.38.
This behavior can be observed for various nails in different locations in the wall and does not occur on other walls in the apartment.
I am not sure what to make of it. Is it an error in my measurement or normal behavior when measuring close to a wire? Or do I need to call an electrician asap?
For completeness, here's a picture of my setup and first reading.