Magnetostrictive Torque Sensors — Derivation of Transducer Model

Current worldwide development activity and potential markets for magnetostrictive, noncontact, torque sensors are reviewed first. Then, a general model for the sensor is derived, and equivalent electrical and magnetic circuits for the sensor are developed. The model is defined in terms of a basic single-branch magnetostrictive sensor element, combinations of which serve as models for multi-branch sensors.

Key assumptions are made that permit simplification of model equations. Procedures for reliable evaluation of magnetic permeance parameters (essential for insuring accuracy of the model) are also given.

Physical origins of the sensor output signal are described, and discussion of characteristic behavior of magnetostrictive sensing-member materials are given. It is shown that all practical sensors include some means of compensation to average out characteristic nonideal properties of magnetostrictive sensing materials.