| 摘要 |
<p>PURPOSE:To detect the positions of exciting coils fast by providing two exciting coils at an axial interval, generating two magnetic fields alternately, and detecting their vertical and horizontal positions at the same time. CONSTITUTION:The exciting coils 11 and 12 which generate magnetic fields are arranged in a tube 3 buried in the ground at the proper length interval in the direction of the tube axis. Then a 1st oscillator 41 oscillates at a specific frequency and a 1st exciting current obtained by amplification 51 is supplied to the coil 11. Further, a 2nd oscillator 42 oscillates at a frequency which is twice as high as that of the 1st exciting current and a 2nd exciting current obtained by amplification 52 is supplied to the coil 12; and the maximum value of its waveform is synchronized with the maximum or minimum value of the 1st exciting current. The coils 11 and 12 which are excited with those currents generate the 1st and 2nd magnetic fields which are in the same direction and opposite directions alternately. Relative positions in two orthogonal directions are detected at the same time from the results of detection 61 and detection 62 according to the synchronism timing.</p> |
