Parameter estimation in dielectrometry measurements

Interdigital dielectrometry is used for non-destructive evaluation of material properties. Spectroscopic analysis of frequency-dependent dielectric properties increases sensitivity and selectivity of measurement of many physical variables (e.g. moisture, porosity, density, and aging status) that are correlated with changes of dielectric properties. This paper presents a convenient algorithmic methodology of analysis and visualization of properties of frequencydispersive materials. Analytical expressions for the simple case of a Maxwell parallel-plate capacitor are developed and contrasted with parametric numerical models of interdigital sensor probes. The visualization of these parametric spaces helps develop intuition and understanding of dielectric measurement results in more complex cases. In particular, loss of sensitivity in different frequency regimes, interpretation of negative transcapacitance values, and byproducts of fast inversion procedures are discussed. Experimental data with fluid and solid dielectric samples is presented for illustration of algorithms, proof of principle, and a basic discussion of multiple wavelength measurement sensitivity. References to descriptions of applications of the presented techniques to practical problems are provided. r 2002 Elsevier Science B.V. All rights reserved.