Circular protractor with multi-position scanning heads

摘要

The circular protractor (1) for e.g. setting the relative orientation of a workpiece w.r.t. a machine tool is formed from a circular plate (2) inscribed with the calibration seal (3) having a centre (B). A spindle or shaft of the machine tool having an axis (9) carries the plate (2) and due to imperfect alignment of the assembly a resultant eccentricity (e) exists between the centres (0,9). In order to compensate for errors due to this eccentricity four scanning heads generate sinusoidal signals for comparison by a unit (10) in which their respective phase differences enable compensation for the eccentricity (e) and evaluation of an absolute result.