Fluid level sensing using ultrasonic waveguides

This paper describes non-invasive ultrasonic guided wave systems for fluid level sensing. When a waveguide is immersed in a fluid, the guided wave in the waveguide will be attenuated due to the leakage of waves into the surrounding fluid. The rate of leakage depends on both the material properties of the waveguide and the embedding fluid medium. The energy reduction of the ultrasonic guided waves has been developed as a function of the fluid level. The finite element modelling, design and construction of wave guide sensors for fluid level sensing are presented. Finite element simulations using ABAQUS 6.9 and experiments have been carried out to study the behaviour of the fundamental symmetric Lamb wave mode, SO, and the longitudinal pipe mode, L(0,2), in fluid level sensing. Finite element trends are validated by experiments. Experimental systems were designed and tested successfully for different fluids, such as petrol, diesel, water and glycerine. Guided wave propagation along waveguides of different geometries and various material properties has been studied. Fluid level sensing experiments were carried out for different types of waveguide, such as rods, tubes and plates.