| 摘要 |
PURPOSE: To obtain the subject package prepared by packing magnetic fine granules or fine pieces of magnetic medium together with a food deterioration- protection agent and capable of magnetically detecting the presence of the package of silica gel, etc., in a packaging material for food in a short time with high accuracy. CONSTITUTION: (A) Nonmagnetic granules of food deterioration-protection agent such as silica gel or quick lime and (B) a magnetic material consisting of (i) magnetic fine granules or (ii) fine pieces of a magnetic medium containing magnetic fine granules, a binder and a nonmagnetic supporting material as essential components are wrapped in a packaging material. When an alternative magnetic field is applied on the magnetically detectable package of the food deterioration-protection agent by an exciting device consisting of an oscillator 101, an output amplifier 102 and an exciting coil 103, outputs of a pair of receiving coils 201 become unbalanced. Then, frequency components characteristic to the output signal induced in the receiving coils are included in the signal delivered to a comparator 203 through a differential amplifier 202. |
