Probe for measuring workpieces

Abstract

A probe having a movable member including an elongate stylus and a plate extending in a plane transverse to the longitudinal axis of the stylus. The plate is seated on a seat having a circular edge provided on the fixed member. Displacement of the free end of the stylus, either transversely to or longitudinally of the stylus, is measured by a transducer having an electrical output signal. Like transverse and longitudinal displacements of the free end unavoidably produce unlike signals. To compensate for this, the signal is passed through a voltage divider whose output is made variable by a relay in a circuit containing the plate and the edge as electrical contacts. Transverse displacement of the free end tilts the plate on the edge, thus maintaining engagement therebetween. Longitudinal displacement separates the plate from the edge, thus breaking contact therebetween. The circuit is connected to the relay to vary the output in the sense of producing a signal equal for equal transverse and longitudinal displacements of the free end. In a modification, the plate and seat have four distinct contacts between them which are arranged at the four corners of a square. This arrangement is used to discriminate between the X and Y directions of the transverse displacement of the free end of the stylus.