EDDY-CURRENT SENSOR FOR COIN EVALUATION

摘要

An improved eddy-current sensor for a coin validator uses a thin ferrite plate having a suitable aspect ratio for two coils. One of them serves to generate magnetic field and the other serves to produce a voltage if there is a coin with eddy-currents in it. The first coil is short cylindrical one and is placed in the middle of the biggest surface of the plate. Its axis is perpendicular to the plate surface. The second coil is wound around the plate with a half coil at one end of the plate and an opposite half coil at the opposite end of the plate, plate symmetrical about center of the plate. The sensor is positioned in the pathway of the coin validator such that the moving direction of movement of the coin is along the pathway perpendicular to the axis of the first coil and makes with the largest axis of the plate an angle about 45 degrees. - 11 -