| 摘要 |
PROBLEM TO BE SOLVED: To provide a metal detector which enhances the reliability of the detection of a metal piece. SOLUTION: In the metal detector, a transmitting coil 6 and a receiving coil 7 are arranged and installed along he conveyance passage of a specimen 1, the output signal b of the receiving coil 7 is synchronously detected by an excitation signal and a signal which has 90 deg.-phase-shifted the excitation signal, and the metal piece contained in the specimen 1 is detected on the basis of respective synchronous detection signals. The metal detector is provided with a work-phase calculation means 39 which sequentially calculates a work phaseϕS on the basis of the Lissajou waveform of each specimen, charge-amount calculation means 27, 28 which calculate a change amountΔϕS on the basis of the preset reference work phaseϕSS of each sequentially calculated work phaseϕS and a measuring-phase adjusting means 37 by which the relative phase between an excitation signal applied to the transmitting coil 6 and an excitation signal applied to respective synchronous detectors 9a, 9b are changed equivalently by using the calculated change amount and by which the work phase calculated on the basis of the Lissajou waveform 15 is approximated to the reference work phase. |
