Contactless ultrasonic monitoring of gases in sealed containers - by detection and analysis of higher order reflected waves

摘要

A contactless method of monitoring the physical characteristics and conditions of gases in hermetically sealed containers involves the transmission of periodic ultrasonic waves through the container walls and their subsequent reception. It is realised using equipment operating independently of the container size. No internal modifications to the chamber or openings in its wall are required. The density and speed of sound in the gas are measured to give an indication of the pressure and type of gas in the container. The ultrasonic waves are directed at the wall at a small angle of incidence but not perpendicularly using a first electroacoustic transducer. Reflections of high order occur at the container wall gas boundary. Only higher order reflections are detected by a second electroacoustic transducer for subsequent analysis.