| 摘要 |
1,142,544. Ultrasonic liquid-level gauge; ultrasonic coupling. MARINE MOISTURE CONTROL CO. Inc. 23 June, 1967 [22 Aug., 1966], No. 29035/67. Headings H4D and H4J. In a liquid level gauge the echo time of an acoustic pulse transmitted along wire 7 by transducer 6 and reflected at an impedance discontinuity provided by float 21 is determined on oscilloscope 14. For gauging the level of an inflammable liquid in a tank (Fig. 4), the transducer is mounted in an explosion-proof chamber 37 fixed to the tank and is coupled to the wire by a tapered acoustic waveguide 6<SP>1</SP> effectively acoustically isolated from the chamber. An acoustic delay line 34, formed by wrapping the wire round a drum surfaced with plastics foam, and a time gate circuit 9 are used to eliminate the disturbing effects of echoes arising from acoustic impedance mis-matches in the coupling between the transducer and the wire.
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