| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a metal detecting device capable of detecting a ferrous metal and a nonferrous metal respectively by itself with high sensitivity. SOLUTION: A transmitting coil 5 is driven to generate alternating magnetic field, two receiving coils 6A, 6B are arranged to receive the alternating magnetic field, signals induced in the receiving coils 6A, 6B are changed by the effect of a metal mixed in an inspected object 7 passing through the magnetic field, and the metal is detected by this metal detecting device. The transmitting coil 5 is driven by a circuit system driving the transmitting coil 5 at two frequencies 1A, 1B in turn in time division, the unbalanced output signal of the difference between voltages V1 and V2 induced in the receiving coils 6A, 6B is extracted in time division to separate two frequency components, and a ferrous metal and a nonferrous metal are detected with high sensitivity by the metal detecting device.</p> |
