DETECTION OF A METAL OR MAGNETIC OBJECT

摘要

The invention relates to a measuring device (100) for detecting a metal object, comprising two emission coils (125, 130) for producing superimposed magnetic fields, a device (135) for determining a differential voltage between the emission coils, and a control device (110-120. 145-160) for supplying the emission coils with alternating voltages such that the value of an AC voltage component of the differential voltage, which is time synchronised with the alternating voltage, is minimised. Said control device is configured to detect the metal object when the ratio of the alternating voltages does not correspond to the ratio of the impedances of the emission coils when the metal object is not there.