Magnetism detecting apparatus and magnetic material identifying apparatus

摘要

A detecting apparatus for reading the magnetic strip (10) on a card (30) compensates for coercivity variations by employing two magnetizing coils (8) wound in opposite senses on the magnetic poles (11 and 12) and two detecting coils (9) coupled to the magnetizing coils (8) and which are also wound in opposite sense on the magnetic poles (11 and 12). Differential output from the detecting coils (9) represents a shift from normal in the coercivity or permeability of the magnetic strip so as to permit compensation for the shifts due to factors such as a warped card or dust intervening thereby permitting accurately identifying whether or not the magnetic strip (10) on the card (30) is a high coercive force type or a low coercive force type. <IMAGE>