A novel liquid-level measurement method based on electromagnetic acoustic guided waves

In this paper, we propose a non-contact liquid- level measurement method based on guided waves implemented by an electromagnetic acoustic transducer (EMAT). Two EMATs with a center-to-center distance of 350 mm are placed on the aluminum alloy plate of the tank, and a meander-line-coil carrying a 403 kHz signal is used to measure the liquid level without contacting the liquid. Out-of-plane and in-plane displacements were calculated to optimize the parameters of the EMAT coils, and the arriving time of the echoes from the liquid surface is used to estimate the liquid-level. The detection sensitivity of 1.21 μs/mm and 2.42 μs/mm were achieved for once-reflection mode and twice-reflection mode, respectively, and the relative error of the liquid-level measurement is less than 4%. Based on these results, the proposed method can be used for liquid-level measurement, and provides a potential to measure the fluid properties such as density, acoustic impedance and so on.