| 摘要 |
A method and apparatus for locating defects in electrical conduits, hollow cables, or pipes above the ground, using a transmission line wherein one of the lines is the conduit under test. A high-frequency AC generator is used to feed the transmission line and set up a standing wave thereon. The transmission line is terminated in a short circuit at the wall of a shielded room. One conduit carries an internal conductor therein, the conductor and conduit forming another transmission line terminated by its characteristic impedance at both ends. A field intensity meter is connected across the characteristic impedance within the shielded room. The location of the defect is determined by monitoring the magnitude of the induced signal on the conductor inside the conduit containing the defect as the applied frequency is increased from a predetermined low value to the frequency at which the first minimum occurs. A formula using this frequency is then employed to calculate the distance from one end of the transmission line to the defect location.
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