Abstract: In a non-contacting angular position sensor (10), an angular positioning of a rotating object, such as a crankshaft, is measured by a Hall effect device (34) that remains stationary in an air gap (33) between two discs (12, 22), both coupled to the rotating object via a shaft (11). A ring magnet (32) is attached to one of the two discs (22) that has a groove (26) therein. The groove (26) varies in width from a wide region (27) to a narrow region (29). There is a transition region (28) between where the groove (26) is narrowest and where it is widest. As the shaft (11) rotates, the Hall effect device (34) senses a magnetic field that varies with the width of the groove (26), thereby measuring the angular position of the rotating object coupled to the shaft (11).

Abstract: A magnetic head and disk tester provides accurate positioning of a magnetic read-write head over a magnetic disk by means of a coarse positioning mechanism and a fine positioning mechanism. The coarse positioning mechanism includes a stepper motor, a lead screw, a nut, rear sliders and a housing. The fine positioning mechanism includes a piezoelectric actuator, slides and a carriage. The positioning displacements are along a linear axis, which lies on a horizontal plane. The carriage is connected to the housing via the fine positioning mechanism, which then moves the carriage with respect to the housing. Two pairs of linear encoders are mounted on the carriage about the axis and measure the position of the magnetic read-write head with respect to the magnetic disk. Each pair is mounted such that the pairs lie in separate horizontal planes.