| 摘要 |
PROBLEM TO BE SOLVED: To enhance accuracy for detecting a metallic piece contained in an inspection object. SOLUTION: In this metal detection device, a transmission coil 6 impressed with an excitation signal (a) of an alternating current and a reception coil 7 differentially connected to the transmission coil 6 are arranged along a conveyance path of the inspection object 1, and the metallic piece contained in the inspection object is detected on the basis of an output signal (b) of the reception coil 7. The metal detection device is equipped with frequency diffusion means 30 and 31 for diffusing a frequency of the excitation signal (a), frequency reverse diffusion means 32 and 33 for reversely diffusing a frequency of the output signal (b) of the reception coil 7, and a band path filter 33 for removing a frequency component caused by a noise magnetic field except for the frequency component of the excitation signal contained in an output signal b1 of which frequency is reversely diffused by the frequency revere diffusion means. |
