Noninvasive method for determining the liquid level and density inside of a container having arbitrary dimension and shape. By generating a flexural acoustic wave in the container shell and measuring the phase difference of the detected flexural wave from that of the originally generated wave a small distance from the generated wave, while moving the generation and detection means through the liquid/vapor interface, this interface can be detected. Both the wave generation and wave detection may be achieved by transducers on the surface of the container. A change in the phase difference over the outer surface of the vessel signifies that a liquid/vapor interface has been crossed, while the magnitude of the phase difference can be related to fluid density immediately opposite the measurement position on the surface of the vessel.
FIELD OF THE INVENTION
The present invention relates generally to the measurement of liquid level and density in containers and, more particularly, to the determination of changes in the propagation velocity of sound in the walls of a container as a result of the presence of a fluid. The invention was made with government support under Contract No. W-7405-ENG-36 awarded by the U.S. Department of Energy and the Regents of the University of California. The government has certain rights in the invention.