Capacitive rotary transmitter for controlling and positioning displaced

Abstract

A capacitive linear or rotary transmitter for controlling and positioning displaced objects by measuring the displacement, angle or speed of the displaced object is formed, in one embodiment as a rotary transmitter, by two mutually opposed stators defining a reciprocal spacing, their gap having rotatably arranged in it a rotor which is rotatably coupled to a spindle which is coupled to the displaced object. Capacitive values varying during the rotation of the rotor may be measured in the air gaps produced in each case between one stator and the rotor, and the other stator and the rotor. To attain a superior degree of precision and resolution, coatings are so arranged on the rotor and the stators, as to produce at least two concentric annular areas, of which one area forms the measurement track of a coarse measuring system and the other area forms the measurement track of a precision measuring system. The digitally determined values of the coarse measuring system are so combined with the values of the precision measuring system as to yield an unequivocally defined absolute value for the angle of rotation. This is attained by the fact that the coupling capacitances generated by mutually associated coatings of the rotor and stators follow a course during the rotary displacement of the spindle which is sinusoidal in parts and that by addition of several reciprocally displaced capacitance graphs which extend sinusoidally in parts and are provided with different prefixes, an approximately purely sinusoidal capacitance graph is generated with a cycle depending on the number of measurement tracks.