Contactless magnetic sensor for measuring angular displacement

摘要

A sensor for measuring angular displacement has a central axis (3) about which a permanent magnet armature (2) with north and south poles (4, 5) is free to rotate in either direction such that its flux provides an index of its orientation detected by eg. a Hall element (6). A practical assembly is illustrated in which the two fixed pole shoes (8, 9) which encircle the magnetic armature (2) are shaped to limit the airgap and thereby inhibit leakage to maximise the flux density appearing at the sensor (6). Alternative configurations include a disc armature, refinements of magnetisation and variable geometry to assist calibration.