MAGNETISED TORQUE TRANSDUCER ELEMENTS

摘要

The problem of magnetoelastic circumferentially-magnetised torque transducers having a zero output magnetic field at zero torque is solved by pre-torquing. This entails circumferentially magnetising the transducer element at a predetermined torque. The technique is advantageously applied to a pair of transducer elements (32, 34: 62, 64) whose outputs are combined (Fig. 6a: 76) 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-magnetisation are discussed. A circuit (Fig. 8) is disclosed for combining the signals to obtain a reference level (84) for gain control of the combined output signals Vo from the two transducer elements (60, 62). 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 magnetisation (Fig. 10a). Another is radially spaced magnetisation (Fig. 12a: Fig. 13).