Mathematical Modeling of the Low-Frequency Range Changes in Dielectric Constant Measurements Due to Settling and Pressure

Abstract

Prior research has shown the effectiveness of dielectric mixture equations such as the Landau-Lifshitz, Looyenga equation for predicting and correcting the effects of density changes in grain at frequencies above 1 MHz. However, the dielectric properties of grain samples vary widely and seemingly unpredictably at low frequencies—especially with changes in density due to pressure or settling. The usual presentations of relative dielectric constant, dielectric loss, loss tangent, or conductivity versus frequency fail to yield much physical intuition regarding the nature of the differences in dielectric characteristics. This paper describes low frequency dielectric constants of yellow-dent field corn samples using Argand diagrams (dielectric loss versus dielectric constant) and identifies a set of parameters that enable automatic fitting of the data and that yield some insight into the physical changes responsible for the observed dielectric differences.