| 摘要 |
Embodiments of the present invention provide an electromagnetic sensor (400) for detecting a microstructure of a metal target, comprising: a magnetic device (410, 420) for providing an excitation magnetic field; a magnetometer (430) for detecting a resultant magnetic field induced in a metal target; and a calibration circuit (450, 551, 552, 553, 554) for generating a calibration magnetic field for calibrating the electromagnetic sensor, wherein the calibration reference magnetic field is generated by an electrical current induced in the calibration circuit by the excitation magnetic field. |
