Magnetic transducer element and method of preparation

Abstract

A magnetic transducer element is formed in a portion (22) of a shaft (20) by an axially-oriented magnetic source (30) comprising a U-shape permanent magnet or electromagnet assembly, the gap (g) between the poles of which is small compared to the pole width (w). The source (30) is brought up to the continually rotating shaft (20) from a distance (D1) to a position closely proximate (D2) the shaft (20) and then retracting the source (30). With an electromagnet the mechanical movement may be emulated by controlling the energising of the electromagnet. An annular, surface-adjacent zone of axially-directed magnetisation is created whose external detectable field (40) has a distribution in the axial direction which shifts axially under applied torque. An axial or radial component may be sensed as a measure of torque. A method of preparing the shaft for magnetisation (magnetic-cleansing) and a post-magnetisation procedure is disclosed.

Dependencies are inferred from the claim text.