| 摘要 |
<p>PURPOSE: To obtain a magnetic head device and a magnetic hysteresis characteristic measuring method for judging a paper money, etc., without using an erasion head. CONSTITUTION: The first head to be engaged with the banknote 11 is a saturation recording head 31 and, then, successively a saturation reading head 32, a non-saturation recording head 33 and a non-saturation reading head 34. A magnetization M is generated in a magnetization layer by the saturation recording head 31 and the saturation reading head 32 measures a saturation residual magnetic field. After that, the non-saturation recording head 33 impresses the magnetic field in an opposite direction, then the non-saturation reading head 34 measures a residual magneticism. A polarity is made to be opposite in a demagnetization magnetic moment measured by the non-saturation reading head 34 when the paper money is the true one. When the banknote is the false one and saturation coersive force is high, that is, when the demagnetization is not smoothly executed, the magnetic moment of the false banknote is reduced to be the 60% of a saturation but the polarity is not inverted. Thus, the forged paper money high in saturation coersive force is identified.</p> |
