Verfahren und Vorrichtung zur Hochgeschwindigkeitsmessung und Kennzeichnung von magnetischen Materialien

摘要

To validate a document carrying marks comprising magnetic materials an oscillator (1) generates a low frequency signal supplying emitter windings (2). Receiver windings (3) are joined to an amplifier (4) that has two outputs (S1) and (S2), the latter yielding a signal (X) used as time reference, and the former yielding, after processing, two signals (Y) and (Z), which are all inserted in a microprocessor (10) which generates signals (13) accepting or rejecting the document. The microprocessor (10) selects the most favourable cycles where signal (Z) is at its highest. <IMAGE>