Banknote ferromagnetic security strip testing - involves magnetising strip in different ways and signals are compared with reference values

摘要

The strips are tested by detection of the direction of a magnetic anisotropy and/or measurement of the hysteresis loop. The strip is magnetised bya first directed magnetic field of a certain intensity, with one field component running along the strip, and the other across it. The strip magnetisation is measured in at least two co-ordinate directions and the signals compared with required values, detecting a preferred magnetisation direction. Then the strip is magnetised in opposite direction to its polarity, and magnetisation measured in at least one direction. Signals are compared with required values.