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As the name suggests a wall detector detects studs behind the surface of a wall. The more advanced scanners have multiple modes that detect studs, metal, live AC wiring, non-ferrous metal (such as copper pipe) and ferrous metal (such as rebar).
Detection is achieved using two different methods:
1. Magnetic
Uses powerful magnets to pinpoint the location of screws or nails in a stud. Therefore it doesn't detect the stud itself but rather the hardware that attaches the wall material to the stud.
2. Electronic
Electronic stud finders rely on sensors that detect changes in the dielectric constant (the relative permittivity) of the wall. This changes when the sensor is over a stud. The lower reading indicates the presence of a stud in the wall and this data is displayed on an LCD screen.
http://www.makatechnologies.com/
