| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a metal detection apparatus by which a mixed metal existing inside an object to be inspected can be detected with high sensitivity regardless of a magnetic metal or a nonmagnetic metal even in the case of the object to be inspected, which is wrapped with a nonmagnetic metal whose thickness is comparatively thick such as an aluminum foil or the like. SOLUTION: The apparatus is provided with an oscillator 1 which outputs an AC signal, with a transmitting coil 2 which generates an AC magnetic field by using the AC signal from the oscillator 1, with a first receiving coil 3a and a second receiving coil 3b which are wound coaxially with the transmitting coil 2 and which induce unbalanced signals due to the existence of a metal in an object W, to be inspected, passing inside a magnetic field generated by the transmitting coil 2, with a detection circuit 7 which detects the unbalanced signals from the first and second receiving coils 3a, 3b and with a phase shifter 8 which changes the phase of the AC signal from the oscillator 1 and which supplies a detection signal to the detection circuit 7. In this case, a mechanism 5 which adjusts positions of the transmitting coil 2 and the receiving coils 3a, 3b, which are wound coaxially, in such a way that the center of a nonmagnetic metal as the wrapping material of the object W to be inspected is passed through a part near its axial center.</p> |
