| 摘要 |
PURPOSE:To detect the displacement of cutting edge correctly and easily by a method wherein magnetic field is generated to offset the horizontal component of the magnetic field which influences on a magnetic field detector from the cutting edge at a magnet generating source. CONSTITUTION:The detecting part 4a of the magnetic field detector 4 which detects the displacement in horizontal direction of the magnetic field induced by the horizontal magnetic component of the terrestrial magnetism is equipped to the main body of the cutting edge 3 for the ground excavation. The generating source 5 of magnetism is equipped together with the detector 4a to induce the magnetic field in the horizontal direction from the cutting edge 3 to the detecting part 4a of the magnetic field detector 4. The electric current for the magnetic cores 5a, 5b is supplied by the source of direct current 5 being variably controlled by the current regulators R1, R2 independently. Thus equipped, the optimum point where the magnetic field which affects from the cutting edge 3 to the detector 4a is offset most efficiently is determined by controlling the direction and the magnitude of the composite vector of magnetic field generated by the magnetic cores 5a, 5b. |
