Detecting and processing circuitry for magnetostriction type torque sensor

A signal processing circuit for a torque sensor, comprising:

• a) at least one detection coil fixed to an external rigid body, and installed around a magnetostrictive shaft, said magnetostrictive shaft being interposed between ends of a rotating shaft so that its permeability is varied according to a direction and magnitude of the torque applied to the magnetostrictive shaft via the rotating shaft and so that an inductance of said detection coil is accordingly varied;
• b) an oscillator which is so constructed as to generate and output a reference waveform having an alternating voltage;
• c) an inverting circuit, connected to said oscillator via a resistor and having a negative feedback circuit connected between an input end thereof and an output end thereof, said feedback circuit having the detection coil;
• d) a phase shift circuit which is so constructed as to output a reference signal having a phase shifted by a phase difference of 1/4 period with respect to the reference waveform derived from said oscillator;
• e) a detector to demodulate an inverted signal output from the inverting circuit on the basis of the reference signal derived from said phase shift circuit;
• f) an integrator to integrate an output signal of the detector to compensate for an iron loss generated in the detection coil so that an integrated output signal indicates a signal corresponding to the inductance of the detection coil without a presence of the iron loss generated in the detection coil.