Theoretical analysis and modeling of Thickness-Expansion Mode (TEM) sensors for fluid characterization

In this paper, the principles of Thickness-Expansion Mode (TEM) resonators for the characterization of fluids are described. From the measurement of the resonance parameters of a TEM piezoelectric transducer, the compressional acoustic impedance of gases and liquids can be determined. Since the propagation of mechanical waves into the fluid is not necessary, information in a wide range of frequencies can be obtained. Alternatively, these sensors can be driven in combination with other ultrasonic techniques to simultaneously determine the density, speed of sound and viscosity of samples. Some potential applications include the probe monitoring of processes and the characterization of fluids under harsh conditions. The main experimental criteria for the design and construction of high-resolution impedance meters (such as piezoelectric material, protective coating or thermal response) have been studied using equivalent electrical circuit modeling and finite element analysis.

► Theoretical analysis of TEM resonators for fluid characterization.
► Numerical analysis of TEM resonators using 2-D Finite element.
► Influence of resonator characteristics over fluid characterization.
► Evaluation of measuring errors coming from experimental.
► It is shown that protective coatings can be used for TEM sensors.