| 摘要 |
1,149,284. Leak detecting. SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ, N.V. July 10, 1967 [July 12, 1966] No.31707/67. Heading G1S. [ Also in Division H4] In a pipe-line leak detector, a measuring device passed through the pipe-line monitors detected acoustic signals in two frequency bands, one of which is at or near the predominant frequency generated by leaks and the other of which is above this frequency. Leak noise and background noise can thus be distinguished, since leak noise is stated to decrease sharply in intensity above the predominant frequency whereas background noise is not significantly different in the two frequency bands. In one embodiment the outputs of two tuned amplifiers (43KHz and 53KHz) fed simultaneously from a microphone are integrated and then compared in a differential voltmeter, and the difference voltage is recorded. In a second embodiment the equipment is switched alternately between the two frequency bands a few hundred times per second. Alternatively, signals in the two channels are recorded on tape for subsequent play-back and comparison. |
