Magnetized torque transducer elements

Abstract

The problem of magnetoelastic cirumferentially-magnetized torque transducers having a zero output magnetic field at zero torque is solved by pre-torqueing. This entails is circumferentially magnetizing the transducer element at a predetermined torque. The technique is advantageously applied to a pair of transducer elements () whose outputs are combined (FIG.) to provide a range of measurement of torque (clockwise and counterclockwise) including zero torque. Various combinations of direction of pre-torque and direction of circumferential-magnetization are discussed. A circuit (FIG.) is disclosed for combining the signals to obtain a reference level () for gain control of the combined output signals V o from the two transducer elements (). Also disclosed is the application of the invention to other forms of torque transducer element in which a magnetic field is stored. One form is longitudinal magnetization (FIG.). Another is radially spaced magnetization (FIG.: FIG.).