Quantitative and Qualitative Characterization of Liquid Materials

In this chapter, broadband microwave reflectometry (BMR)-based methods for measuring simultaneously the levels and the dielectric characteristics of liquid materials are presented. First, an approach based solely on time domain reflectometry (TDR) measurements and on the analysis of TDR waveforms is described. Secondly, a further enhancement of this method is accomplished by resorting to the combination of TDR with frequency domain reflectometry (FDR). Also this method provides, in one shot, the level and the dielectric permittivity of the considered liquids (this time, the complete spectral signature is obtained in terms of Cole-Cole parameters). This approach is considered the optimal solution especially when dealing with dispersive media. In this second measurement method, the accuracy is enhanced also through the adoption of a transmission line (TL) modeling of the measurement cell and through the realization of a custom-made fixture that allows performing short-open-load (SOL) calibration measurements. Finally, BMR-based measurements of the dielectric characteristics are extended to edible liquids: in particular, vegetable oils are considered. Reported results show that all the proposed methods have strong potential for possible practical implementation in the field of industrial monitoring. It will be evident how, in all the considered approaches, the design of the probe is crucial for enhancing the final measurement accuracy