Acoustic impedance measurement using PLSR based analysis of ultrasonic signals

Mechanical properties of a liquid affect the wave shape of transmitted pulses. This interrelation can be statistically modeled using Multiple Linear Regression. The Partial Least Squares approach presented in this paper derives a model to indirectly measure the acoustic impedance of a liquid by analyzing the shape of transmitted pulses. It is shown that the acoustic impedance is an appropriate quantity to derive process parameters. The applicability of the proposed signal processing is demonstrated on measuring the density of an aqueous glycerin solution as well as on determining the glycerin concentration. The obtained values are compared to measured references. The influence of disturbances and parameter changes is highlighted. The influence of transducer properties is discussed.