Helical Waveguide Sensor for Fluid-Level Sensing Using L(0, 1), T(0, 1), and F(1, 1) Wave Modes Simultaneously

This article studies an ultrasonic waveguide sensor using thin stainless-steel wire with helical configurations for measuring various fluid levels. The fundamental longitudinal
${L}$
(0, 1), torsional
${T}$
(0, 1), and flexural
${F}$
(1, 1) wave modes were used simultaneously through the waveguide using a shear transducer. Initially, a finite element model (FEM) was used to study all three wave modes’ behavior when we immersed the waveguide in an air medium and immersed it at different fluid levels. Similarly, we experimentally measured the various fluid levels using water, petrol, and glycerin. The fluid-level measurements were based on the drop in amplitude and the change in time of flight (
$\delta $
TOF) of all three wave modes. Multiple experiment trials (T1, T2, and T3) were conducted for each case to ensure the repeatability of the helical sensor. The sensor’s error analysis was studied using all three wave modes, and the average error was less than 2.5%. We identified better sensitivity using the
${F}$
(1, 1) wave mode for fluid-level measurement compared to the other two wave modes. Minute fluid-level measurement experiments were conducted for every 0.5-mm increment of the fluid level using the
${F}$
(1, 1) wave mode. This method can be used in highly flammable or hazardous regions, such as fuel tank level sensing, temperature, and viscosity measurement simultaneously, especially in oil and gas industries.