A method for measuring liquid level using the flexural vibrations in a rod

概要

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Here we propose a novel measuring method of the liquid level in a water tank using the flexural vibration in a rod. With changing the water level, the frequency response of the vibrating rod is also changed due to the change of its radiation impedance. The flexural vibration along the rod can be generated by PZT elements attached on the end of the rod. The size of the vibrating rod and PZT elements were determined via the finite element analysis (FEA) so as to maximize the vibration displacement amplitude of the rod. In the FEA model considering the acoustic radiation of the vibrating rod in the cylinder, the frequency responses of the vibrating rod were calculated with changing the water level. The experiments were carried out with several configurations designed by the FEA. By sweeping the driving frequency from 5 to 7 kHz, the frequency characteristics of the vibrating rod could be obtained, and the experimental results showed good agreements with the calculated result by FEA. The frequency responses of the rod with several water levels were measured, and it was found that the water level could be estimated uniquely in the water level range of 0 to 1,550mm.
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