| 摘要 |
<p>PROBLEM TO BE SOLVED: To easily perform the calibration of detection sensitivity without using a test inspection objective body. SOLUTION: In this metal detector, a transmission coil 6 impressed with an excitation signal of an alternating current and a reception coil 7 differentially connected with the transmission coil 6 are arranged along a conveyance path 2 of an inspection objective body 1, synchronous detectors 9a and 9b perform synchronous detection on an output signal of the reception coil with an excitation signal, and a metal piece included in the inspection objective body 1 is detected on the basis of a signal value of an output signal of the synchronous detectors. It is provided with calibration signal impressing means 28, 34a, 34b, and 18 impressing a calibration signal having the same signal level as the output signal of the reception coil in regard to the inspection objective body (test piece) to the synchronous detectors, and a calibrating means 31 calibrating a conversion factor for converting the output signal of the synchronous detectors to the size of the metal piece on the basis of the impressed calibration signal.</p> |
