System for measuring the longitudinal or angular displacement of a

Abstract

A system for measuring the longitudinal or angular displacement of a movable component with respect to a reference position, wherein an increment scale track is supported at a scale carrier affixed to the component, and associated therewith are stationary increment-reading means, an increment counter and electrical circuits for counting properly with respect to the direction of motion of the component the algebraic sum of the increment units traversing in front of the increment-reading means. The scale carrier supports at a second scale track parallel to the increment scale track a multiplicity of absolute-value marks, each of which is spaced from the next following mark by a particular spacing characterizing the absolute value of its distance to the reference position, and which spacing is counted in increment units. The measuring system is constructed to determine the characteristic number of increments which have been algebraically counted at the increment counter from the traversing of any absolute-value mark to the traversing of the next following absolute-value mark in front of a mark-reading means, and to derive from such characteristic number the corresponding absolute value of the displacement of the movable component with respect to the reference position. The absolute value associated with a given characteristic number is fixed in an appropriately programmed read-only storage means. The counter state of the increment counter is then set to the correct absolute value as delivered by the read-only storage means.