Vernier device of the digital display type for a universal parallel ruler

摘要

A vernier device of the digital display type for a universal parallel ruler is disclosed comprising a slit protractor having slits arranged at the same visually readable protractor and a intervals as those intervals for the protractor graduations, the slit protractor being provided on one of a stationary portion and a rotatable portion of a scale operating head. A slit vernier protractor having slits at other intervals for vernier graduations is provided, the slit vernier protractor being provided on the other of the two portions of the operating head. An encoder consisting of photoconductive elements and corresponding light-emitting elements is provided with the slit protractor graduations and the slit vernier graduations interposed therebetween wherein a fine vernier angle is digitally displayed for reading on the basis of a signal representing a coincidence between a slit vernier graduation and a corresponding slit protractor graduation.