| 摘要 |
<p>PURPOSE:To enable the discrimination of a slight difference in the generating frequency of rust by expanding the high electric conductivity area alon of a cable to be inspected to obtain a rust detection signal. CONSTITUTION:With a rust detection signal transmitter and a receiver, an output of a rust detection coil 51 is transmitted and detected, chopped with a modulator 56 comprising an FET and then, FM modulated to be transmitted. The signal FM detected with an FM receiver 70 is rectified into DC with a rectification circuit 71 to be the original rust detection signal. The rust detection signal is required in the following cases: where the conductivity of the material is indicated as it is with no rust on the surface of a cable to be inspected, the conductivity lowers with the generation of some amount of rust and the conductivity falls below a specified value with the generation of rust above a fixed amount. So, the signal below the specified value is cut with a differential amplifier 72 and in stead, only the signals above the specified value are amplified with an amplifier 73 to ensure judgement at a high accuracy. Then, the output signal thus obtained is determined with 2 level comparator 75 what level it is at.</p> |
