Search coil assembly for electrically conductive object detection

Claim 1

A search coil assembly having an excitation coil producing an alternating magnetic field, an area-type receiver coil located in the magnetic field and including a plurality of windings, the receiver coil having a total area composed of at least two partial areas displaced relative to each other, voltages induced in the winding located in the partial areas substantially compensating each other at the output of the receiver coil by forming difference voltages, comprising: the receiver coil including at least one carrier layer of electrically insulating material common to the at least two partial areas; the receiver coil windings being deposited at the periphery of the partial areas in the form of a band of conductive circuit tracks arranged side-by-side in a generally figure-8 configuration; the individual windings including pairs of conductor loops, each loop of each pair overlying a respectively different partial area, the senses of winding of the conductor loops of a pair being opposed to each other; the carrier layer having first and second oppositely directed surfaces with the conductor loops of each pair being located on said first surface; and means for interconnecting windings of respective pairs of loops to one another located on the carrier layer second surface.