Enhancing the ultrasonic waveguide sensor's fluid level sensitivity using through-transmission and pulse-echo techniques simultaneously

This paper reports an ultrasonic waveguide technique using U-shaped configurations to measure the fluid level. The longitudinal L(0,1) wave mode was propagated in the waveguide using through-transmission (TT) and pulse-echo (PE) techniques simultaneously using a single shear transducer. Initially, we used the Finite Element Method (FEM) to study the waveguide's wave propagation behavior while immersed in various fluids. Develop the level sensor using the waveguide's first and second pass signals, corresponding to TT and PE. We have performed the level measurement experiments based on the drop in amplitude and change in time of flight of the received sensor signals. Studied the sensor's sensitivity using TT1, PE1, TT2, and PE2 signals (1 and 2 represent first and second pass signals, respectively) with different fluid levels (petrol, water, castor oil, and glycerin). A comparison study was performed between straight waveguides using PE and U-shaped waveguides using TT techniques to find the limitations of waveguide sensors. During level-sensing experiments, the average error for U-shaped and straight waveguides was identified as 3.5% and 5.6%, respectively. We studied signal attenuation from straight and U-shaped waveguide sensors based on the sensor surface and dead-end region. In the designed U-shape waveguide, only the wave leakage effect was considered, avoiding the dead-end reflection during the immersion of the sensor in liquid and allowing for more fluid depth measurements. In addition, the U-shaped waveguide was further used for fluid-level sensing using three wave modes [L(0,1), T(0,1), and F(1,1)] simultaneously. This sensor can monitor fluid levels in hostile environments and inaccessible regions of power plants, oil, and petrochemical industries.