Patent ID: 6341534
Filing Date: 2002-01-29
Classification: G01D,G01L,Y10S

Abstract:
A dual channel magnetoelastic torque sensor comprising:a shaft adapted to receive a torque; a pair of oppositely polarized magnetoelastic bands provided on the shaft, the pair of magnetoelastic bands producing a magnetic field in response to a torque being applied to the shaft; a high temperature plastic housing circumscribing the shaft having a plurality of pockets and overlaying the pair of magnetoelastic bands; at least a first pair of serially connected magnetic flux detectors comprised of small diameter solenoid coils disposed inside of said pockets, each magnetic flux detector being adjacent to a respective one of the pair of magnetoelastic bands and responsive to the magnetic field generated by the magnetoelastic bands to produce a signal; the magnetic flux detectors being arranged such that a signal induced in one of the magnetic flux detectors by a static magnetic field is of equal and opposite polarity to the signal induced in the second magnetic flux detector; a triangular wave generator connected to a first end of the at least first pair of serially connected magnetic flux detectors; the triangular wave generated by the triangular wave generator having a predetermined maximum and a predetermined minimum voltage value; an amplifier having at least two inputs and an output; a first multiplexer means connected between the pair of magnetoelastic flux detectors and the amplifiers for alternately switching the two inputs of the amplifier between connections to opposite ends of the pair of serially connected magnetic flux detectors at a frequency corresponding to the second harmonic of the triangular wave; an integrator circuit connected to the output of the amplifier, the integrator circuit integrating the output of the amplifier to generate a signal indicative of the torque applied to that shaft; an offset correction generator connected to the opposite end of the serially connected magnetic flux detectors, the offset correction generator generating an offset signal in response to the output of the integrator circuit, the offset signal equalizing the output second harmonic signals produced by the amplifier; and an electronic control connected to the triangle wave generator and the multiplex means, the electronic control generating a first signal controlling the frequency of the triangular wave generated by the triangular wave generator and generating a second signal synchronized with the first signal, the second signal activating the multiplexer means to switch the connections of the inputs to the amplifier to the opposite ends of the pairs of serially connected flux detectors at a frequency corresponding to the second harmonic of the triangular wave.