I wanted to install a shelving system into my closet. The stud finder seems to detect live wires over a large area (approximately 4 by 4 feet!) The closet is in the basement, with no power outlets except the light fixture. But the stud finder's signal turns on about 3 feet above ground and continues all the way to the ceiling. I checked it with two different stud finders (same result). Question: is this even possible??? That there is so much going on behind a closet wall? I don't want to drill through any wires, but honestly, a closet like this, without shelves is quite useless...
With most live wire detectors there is an adjustment wheel that sets the sensitivity. If you have this turned up too high it won't give a localised reading.
Usual procedure is to turn the device on, then in free air, adjust the sensitivity up until the detector emits a tone, then turn back until it turns off.
Sensitivity may be affected by metalwork on the other side of the plasterboard/drywall. So you may need to back off the sensitivity further.
Test the detector somewhere else. For example if you have a power outlet and know the cables run vertically from that outlet, use that area to adjust the sensitivity to give a good localised indication of the wire run. Then try it in your closet.
If you have un-insulated hollow interior walls ("stud walls") and can justify buying, renting or borrowing an inspection camera, you may be able to make a small hole in a "safe" area and use that to locate wooden studs.
It's best to do a visible inspection. Just cut a small hole at the level of a normal power outlet and use a flash light and mirror to look up in the cavity wall. After the inspection, either patch the wall/paint or just install a blank plate over the hole. If you don't have a mirror, a camera phone with a flash works pretty well.