ELECTROMAGNETIC INDUCTION SENSOR FOR SURVEYING METALS

摘要

PROBLEM TO BE SOLVED: To improve the sensitivity by detecting a weak change in alternating current magnetic field. SOLUTION: A coil for transmission 1 transmits an alternating current magnetic field in the direction perpendicular to the surveying direction. Coils for receiving 2a and 2b are arranged very close to a core 3 so that the axis direction of cores 4a and 4b face to the surveying direction and their middle point coincides with the center position of the core 3. If there are no metals, the exciting voltage of the cores 2a and 2b become 0. If there are metal in the surveying direction, voltages are excited in the coils 2a and 2b. In this manner, a weak change can be caught. As the coils 2a and 2b are arranged very close to the core 3, the level of the alternating current magnetic field itself detected with the coils 2a and 2b can be raised.