PURPOSE: To prevent the erroneous identification of an article from occurring by reducing a white noise due to an external magnetic field and the function of a detection circuit itself by integrating and averaging a pulse voltage string signal.
CONSTITUTION: Detection coils 7a-7c which detect magnetic flux change according to the reversal of magnetization of a magnetic marker 1 generated by an AC magnetic field as an induced electromotive voltage are connected to a measuring instrument 8 and a personal computer 9 in series. The level of the pulse voltage sequence signal is reduced depending on the relative position relation of the magnetic marker 1 and the detection coils 7a-7c, and it goes to the one equal to or less than the signal level of the white noise, which makes the pattern of the pulse voltage sequence signal difficult to identify. In such a case, the output level of the white noise is reduced by integrating and averaging the pulse voltage sequence signal, and the S/N of the signal is heightened, thereby, the recognition of a pulse voltage sequence and the identification of a pulse voltage string pattern can be performed. In such a way, it is possible to perform the identification of the article by detecting the pulse voltage sequence generated in the detection coil.
KATSUYAMA TERUSHI
MATSUSHITA SHIGETADA
