| 摘要 |
PURPOSE:To detect a non-metallic magnetic material without being disturbed from a metallic material, by using an oscillating circuit of several KHz-several MHz, and detecting the time when the oscillation frequency is reduced. CONSTITUTION:Oscillation frequency of an oscillating circuit 1 is several KHz- several MHz, inductance of a detecting coil 1a is 0.1muH-10mH, and 1-3 pieces are used. When the detecting coil approaches ferrite, inductance of the coil increases and the frequency decreases, therefore, it is reverse case to the case when said coil has approached a metallic magnetic material. This frequency variation is converted to DC voltage V by a PLL circuit 3, and is compared with constant voltage V0 set in advance, of an electric power supply 4, by a comparator 5. In case of V<V0, a signal K is outputted, and a deciding device 6 generates an acoustic signal. In this way, a non- metallic magnetic material is discriminated from a metallic magnetic material and is detected. |
