| 摘要 |
<p>PURPOSE:To eliminate influence by an inspected body itself by performing changeover into a phase angle, preset to every part of the inspected body so as to minimize the level of direct current output by the inspected body itself, in association with the movement of an inspecting body, thereby making unbalanced signals into direct current signals. CONSTITUTION:A detecting device 21 outputs detection signals during the passage of an inspected body W. A time setting circuit 22 is preset with the time (t1, t2) from the detection signal output time of the device 21 to the phase angle changeover and the time (t3) to the time of the rear end part of the inspected body W leaving a receiving coil S2, and outputs pulses after the respective times from its rise. A phase angle setting circuit 23 is preset with phase angles alpha, beta, gamma to be switched as digital value, and outputs alpha at the rising time of the device 21, $ after the time t1, gamma after the time t2 and stops output by the pulse after the time t3. A phase shifting circuit 24 outputs a phase-shifted reference signal, obtained by shifting the phase of a reference pulse from a reference signal generator 11 according to a phase angle indicating signal from the circuit 23, to a wave detecting circuit 15. A circuit 15 performs the synchronous wave detection unbalanced output by signals changed successively in phase, that is, selects such output waveform as to minimize wave detection output by the inspected body W itself.</p> |
