Ultrasonic spectroscopy of liquid filled piezoelectric tube

Abstract

The characterization and classification of liquids through instrumentation is essential

in many industries. As such, measuring the characteristics of liquids is not just useful

as a control parameter within an industrial process; such measurements can also be

used to classify the liquid. Such a sensor is especially practical if it can be connected

in-line with the liquid to be measured, thus minimally influencing flow.

A piezoceramic tube was studied in an attempt to produce a sensor to encompass

exactly those aims. Spectra were taken of liquid-filled piezoceramic tubes. Several

models for this system, both for the piezoceramic tube and the liquid within it, were

then studied to determine an accurate mathematical representation of the measured

spectra. The model ultimately used was a derived equation for the dynamics of the

liquid.

The simulated spectra were optimized to match the actual data, using several techniques

ranging from simple search algorithms to breeder algorithms. The optimization

technique used was based upon the complexity of the model implemented. The effect

of the error calculation method is important and is discussed. From the optimization

results, the speed of sound, density and viscosity of the liquid can be determined to

accuracies of less than 0.2%, 3% and 10% respectively.