Patent ID: 8310237

Claim:
An apparatus for detecting a conductive object, the apparatus comprising: at least one transmitting device operative to generate a first changing magnetic flux; and at least one receiving device operative, in use of the apparatus, to receive a second changing magnetic flux generated by the conductive object in dependence upon receipt by the conductive object of the first changing magnetic flux, the at least one transmitting device and the at least one receiving device being disposed in relation to each other so as to attenuate the first changing magnetic flux received directly by the at least one receiving device from the at least one transmitting device, the at least one transmitting device and the at least one receiving device being mounted on the apparatus for rotation together, the at least one transmitting device and the at least one receiving device being operative to rotate in relation to the conductive object while the first changing magnetic flux is being generated and the second changing magnetic flux is being received, and the receiving device provides an output signal comprising at least one first frequency component corresponding to a rate of movement of the transmitting device and the receiving device in relation to the conductive object.