Capacitive rotary transmitter for controlling and positioning displaced objects

A capacitive rotary transmitter for controlling and positioning displaced objects by measuring any of the three characteristics of displacement, angle, speed, of a displaced object, is formed by two mutually opposed stators defining a reciprocal spacing, the spacing having rotatable in it a rotor which is rotatably coupled to a spindle which is coupled to the displaced object, the rotor having a front side and a rear side, the spacing including a first space between one stator and the rotor and a second space between the other stator and the rotor with electrically conductive coatings on mutually confronting sides of the stators and the rotor, the coatings together with the associated spaces forming capacitors respectively, the capacitance value of which varies with the rotation of the rotor,

• characterized in that,
• the coatings are so arranged on the rotor and the stators that they form at least two concentric annular areas, of which one area forms the measurement track of a coarse measuring system and the other forms the measurement track of a fine measuring system, the coatings of the fine measuring system being periodically arranged with respect to a fraction of 360.degree. on annular tracks of the rotor and stators, and the coatings of the coarse measuring system being periodic with respect to 360.degree., so that the coupling capacitance generated by the mutually associated coatings of the rotor and stators, by the rotation of the rotor, have a graph along the rotor displacement of the spindle which is sinusoidal and that by addition of reciprocally displaced partly sinusoidally extending capacitance graphs tagged with different prefix signs, an approximately purely sinusoidal capacitance graph having a period of 360.degree./n.sub.i is generated, n.sub.i being a positive natural integer and indicating the pole pair number of the particular measurement track and the index i denoting the number of measurement tracks.