Position-measuring device

摘要

in a position-measuring device, a shaft (W) that is connected to a first object (01) is rotatably mounted in a housing (G) connected to a second object (02). The shaft (W) carries a first graduated plate (S1) having a first scale (T1) and a second graduated plate (S2) having a second scale (T2) as well as having a reference mark (R) absolutely assigned to the first scale (T1). A scanning unit (A1) fixed to the housing is provided for the purpose of scanning the first scale (T1). A second scanning unit (A2) is rotatably mounted on the shaft (W) for the purpose of scanning the second scale (T2) and the reference mark (R). Mounted on the housing (G) is a zero sensor (N) whose imaging optics (OT) are rigidly connected to the second scanning unit (A2). In order to reproduce a reference position after interrupted measurements and movements in the case of an arbitrary unknown instantaneous position of the objects (01, 02) relative to one another, the second scanning unit (A2) can, together with the imaging optics (OT), be pivoted relative to the second graduated plate (S2) and to the zero sensor (N) in order to scan the reference mark (R) and the zero sensor (N). The angle between the zero sensor (N) and the reference mark (R) is detected by means of a counter. <IMAGE>