A contactless resistance potentiometer

A contactless resistance potentiometer having two exterior electrodes and a tap for dividing the resistance, characterized in that a photoconductor layer is used as resistance element, the usable surface of the photoconductor layer being delimited by two exterior electrodes and being subdivided by a tapping electrode having a definite geometric course between said exterior electrodes, and a partial surface between the exterior electrodes remaining constant as to its size being electrically active by means of exposure, whereby the distance ratio from said tapping electrode relative to said two exterior electrodes is varied by means of displacing the exposure and thus displacing the active partial surface alongside of tapping electrode, in which a first one of said exterior electrodes essentially lies punctiformly in the center of a circular surface of said photo-conductor layer and that the second one of said exterior electrodes circularly surrounds said circular surface, the tapping electrode describing a path between said two exterior electrodes whose radius is a function of the circular angle and in which the exposed surface is a rotary radial circular segment, and in which a linear interrelationship between the rotation of the exposed circular sector and the resistance divider ratio exists, and that the tapping electrode with its radius r takes a course dependent upon rotary angle (.phi.), upon the smallest radius r.sub.o and upon the largest radius r.sub.1 according to the formula ##EQU5##