Nonlinear Vibration Characteristics of Coriolis Mass Flowmeter

Coriolis mass flowmeter (CMF) is generally regarded as a linear system when the vibration amplitude of the measuring tube is relatively small, but the spectrum of its output signals still show existence of some multiple frequency components. Taking into consideration the nonlinear factors and external excitation, the motion equations of the CMF straight measuring tube are established by properly simplifying the boundary conditions of the measuring tube and integrating the mathematical model of the CMF sensor. In addition, the motion equations are discretized with the Galerkin method, and from the discretized results, it is discovered that the system contains a group of nonlinear factors. By using a laser vibrometer, the state of the closed loop resonant vibration of the measuring tube and the forced vibration of the standard sine signal are measured. The results show that both contain nonlinear factors just as the nonlinear analysis had expected. Experiments have been undertaken to verify the measurement accuracy of the measuring tube with different vibration amplitudes, which evidences that nonlinear influences become more serious with the vibration amplitude rising. The theoretical analysis and experimental results are expected to be of great value for further improvement of CMF performance.