Incremental length or angle measuring system

An incremental measuring system is disclosed in which a reference position can be determined at any time. A rotating carrier body carries an additional incremental graduation for which scanning fields are arranged on a scanning plate. During a calibrating operation an additional marking on the rotating carrier body is used to determine coincidence with an associated scanning field. At this point a measuring value counter is started which counts graduation increments associated with rotation of the carrier body by means of associated scanning fields until the measuring value counter is stopped. This stopping of the counter is controlled by a signal generated on coincidence of an additional marking of the carrier body with the next reference mark on the graduated disc which carries the measuring graduation. Simultaneously, an additional marking of the carrier body reads a code mark associated with the reference mark. Each of the code marks contains in coded form the absolute position of the associated reference mark with respect to the zero point of the measuring graduation. The reference position is determined from the counting value of the increments which are superposed on the absolute position value of the overrun reference mark.