Development of an Inductively Coupled Magnetoelastic Torque Sensor

Application of an inductively coupled torque sensor is described. The active element consists of an electrically conductive wire on which a magnetoelastic material is electrodeposited. This element exhibits a nonlinear impedance with current and also with stress. When mounted onto a shaft, these variations can be processed to provide a measurement of the applied torque. The physical characteristics of the sensor (i.e. small size, low mass, and rugged construction) suggest its use in demanding applications or harsh environments. Because of the magnetic properties of the sensor, inductive coupling can be utilized to provide both excitation and signal detection; thus permitting a contactless method of measuring torque. Additionally, because both the sensor and electronics are not overly complex, the system seems suitable for wide-spread application.

The fabrication and electrical characteristics of the stress sensitive wires as a surface mounted torque sensor are described, as are the external magnetic field excitation, detection system, and signal processing techniques used to determine the applied torque. Test results from an experimental system are presented.