Patent ID: 6999007

Claim:
A position detector comprising: a sensing circuit extending over a measurement path for sensing alternating magnetic field oriented in a predetermined direction; an energizing circuit, different from said sensing circuit, for generating an energizing alternating magnetic field, said energizing circuit having an external high permeability rod extending along said measurement path in a first plane having said sensing circuit but removed therefrom, said rod having first and second excitation coils connected in series and wound around said rod and disposed at opposite ends defining a length of said rod; and a resonator electromagnetically coupled to said sensing circuit and said energizing circuit; at least one of the resonator and the sensing circuit being mounted for relative movement with respect to the other over said measurement path in said first plane that is substantially parallel to said predetermined direction; said resonator being operable, upon energization by said energizing circuit, to resonate and to generate an alternating magnetic field whose magnetic axis lies substantially in said predetermined direction, which resonator magnetic field induces an alternating signal in said sensing circuit; said resonator and said sensing circuit being arranged so that the amount of electromagnetic coupling therebetween varies sinusoidally as a function of their relative positions, thereby causing the amplitude of said signal induced in said sensing circuit by said resonator magnetic field to vary in a similar sinusoidal manner as a function of the position of the resonator relative to the sensing circuit.