Electro mechanical position indicator using relatively moveable coils

Claim 1

Electromechanical apparatus comprising first and second relatively rotatable parts, said first part including two oppositely facing parallel surfaces and said second part including two parallel surfaces each of which extends parallel to, and lies closely adjacent to, a respective one of said two surfaces of the first part, at least one said surface of the first part having secured thereto a first coil and the said two surfaces of the second part each having secured thereto at least one further coil and means for mounting said first and second parts for relative rotational movement so as to cause said further coils secured to the two surfaces of said second part to move along a predetermined path relative to said first coil, the inductive coupling between each said further coil and said first coil being dependent on the relative rotational position of said parts and said coils providing more than one electrical cycle per complete mechanical rotation of said relatively rotatable parts, an alternating current voltage being supplied to said first coil and coupled to said further coils, said apparatus further comprising electronic processing means for producing an output representative of said relative rotational position, said processing means being connected to said further coils and comprising electronic storage means having a plurality of storage locations which are individually addressable in response to addressing signals, means for deriving said addressing signals including counter means for counting said electrical cycles so as to identify the relevant sector of the mechanical rotation of said relatively rotatable parts, the said addressing signals being supplied to an address input of said storage means and said storage means further acting to store correction signals corresponding to respective measured values representative or angular positions in the relevant sectors of said mechanical rotation, and correction means for receiving said correction signals from said storage means and for correcting said measured values in accordance with said correction signals, said correction means providing a said output representing each measured value thus corrected.