Detecting existence of existence or non-existence of nut at hole in metal plate

摘要

The nut presence detector involves producing a magnetic field (52) and the metal mass arranged radially outside the scanning head (46) of the sensor (42) in the metal plate (24) is determined. A signal is then produced, which indicates the existence or the non-existence of the nut (22) at the hole in the metal plate (24). The scanning head has a predetermined impedance, and the alterations of this impedance value are determined. The scanning head (46) is tubular is design and contains an induction coil (54), which is arranged co-axially inside the scanning head (46).