Apparatus for measuring the magnetic strength of magnetic work pieces

摘要

What is disclosed is an apparatus for measuring the relative magnetic field strength of magnetic workpieces such as miniature permanent magnet rotors which, for example, are included in miniature watch motors. The apparatus includes a nonmagnetic shaft member, one end of which is attached to a motor and the other end being positioned in a bearing. The shaft has a reduced portion thereof extending beyond the bearing and located between the poles of an electromagnet which acts as a miniature alternator. Located in the end of the shaft opposite the motor, are inserts for receiving the magnetic workpiece which may be a basic rotor or a rotor/axle assembly. The shaft is rotated at a speed which produces an alternating magnetic field in the electromagnetic pole pieces thus generating an alternating current voltage. This voltage is measured on a digital volt meter or the like with maximum and minimal levels established by calibrating with good and average rotors.