| 摘要 |
The apparatus consists of a mechanical acoustical driver producing sound vibrations in a fluid, such as a liquid or gas, within an enclosed space. A pickup transducer positioned within the tank measures the sound vibrations of the gas within the tank and transmits the same to a lock-in amplifier and a low pass filter. The outputs of the lock-in amplifier and low pass filters are fed to differential amplifiers which amplify the difference between the dynamic fluid pressure changes caused by the sound vibrations and the static pressure. An acoustical resistor is positioned between the pickup transducer and the wall of the enclosed space for providing a fluid passage way therethrough. The acoustic resistor in conjunction with a nonlinear circuit element mounted at the output of the differential amplifiers linearizes the output of the apparatus providing accurate measurements of the material at both extremes of either very small volume or very large volume in the enclosed space. Another embodiment of the invention incorporates a container for a fluid and a pickup transducer positioned therein. An acoustical driver produces sound waves therein which are measured by the pickup transducer and transmitted to a preamplifier and from there to a spectrum analyzer. In place of a spectrum analyzer, a fast fourier transform machine may be substituted. The spectrum analyzer or fast fourier machine detects amplitude changes caused by a fluid leak in the enclosed space.
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