Patent ID: 8850881

Claim:
A method to determine the fill level of material inside a reactor vessel that includes liquid and solid comprising relating a shift of the natural frequencies of wall vibrations to fill level wherein a relationship between frequency shift of wall vibrations and fill level is determined by a) inducing vibration on the wall of said reactor vessel from an external source, b) measuring the vibration signals of said reactor vessel wall as a function of frequency and modal vibration amplitude of said reactor vessel wall, and c) relating the combination of the frequency and the modal vibration amplitude of said reactor wall to the fill level of said liquid and solid; wherein the method utilizes a system consisting of: an acoustic/vibration excitation source, one or more vibration receivers, a temperature reduction rod for each receiver, a signal conditioning and acquisition unit, and a data analysis and display unit, and wherein the relating of the combination of the frequency and the modal vibration amplitude of said reactor wall to the fill level is independent of a location of the one or more vibration receivers on said reactor wall.