Rotation sensor with co-planar velocity and position responsive elements

Abstract

A rotation sensor inlcudes circuitry for sensing both small units of rotation of a rotating body relative to a stationary body and a predetermined angular orientation of the former to the latter, and is designed to prevent electromagnetic interference between the rotation sensor circuitry (FG) and angular position sensor circuitry (PG). The FG circuit defines a full annular ring about the axis of the rotating body whereas the PG circuit covers a relatively narrow annular sector. The FG and PG circuits lie at different radial positions and do not overlap radially. Corresponding PG and FG magnetic rings fixed to the stationary body opposite the PG and FG circuits consist of annular sectors magnetized to alternating polarities. The symmetrical spacing of the FG magnetic sectors matches the angular spacing of FG circuit elements oriented perpendicular to the magnetic flux generated by adjoining magnetic sectors. The PG magnetic sectors match both the spacing and the total angular extent of the PG circuit. As the PG and FG circuits rotate, the corresponding magnetic sectors induce electric fields, resulting in the desired sensor signals. The PG and FG circuits are connected in parallel to a common electrical terminal. Connections from opposite ends of the FG circuit to the common terminal and to the FG output terminal may be curved so as to maximize their length in the magnetic flux region while minimizing their obliquity to the magnetic flux lines.