Co-ordinate digitiser for automatic reading of technical drawings - inductive sensor provides measured position using two wire loop arrays

摘要

A co-ordinate digitiser for use with computerized systems for the reading of technical drawings utilises an inductive sensor. A number of conducting wire loops are arranged in columns with a fixed distance between each other. The loops are located on a plate over which is located a cylindrical coil with a continuously supplied alternating current winding. The sensor loops are represented by two pairs such that when magnetic field is moved the direction of motion may be determined. Comparison of phase between the two loops enables the position to be determined. Two such sensing arrangements located perpendicular to each other provide a full two axis co-ordinate digitisation.