Efficiency Analysis and Application of Improved Method for Heterogeneous Liquids Quality Assessing by Impedance Components

Abstract

Parameters of the total electrical resistance (impedance) are often used for substances properties identification, in particular, for heterogeneous liquids. In such conditions, the quality of the product is compared with the measured impedance (or full admittance) on alternating current [7, 8]. To do this, the industrial meters (RLC-meters), based on equivalent circuits, for example, in accordance with the «Warburg impedance scheme», are used. The disadvantages of such measurement tools are the uncertainty of the measuring circuit model components, the choice limitations of electrical parameters measuring means with the necessary sensitivity, as well as the high cost. Previously, the authors developed a new method of separate determination of active and capacitive impedance components for a heterogeneous fluid. This method is based on measuring at two close frequencies the levels of electric current and voltage with the subsequent calculation of the impedance components by a certain algorithm [1]. It is taken into account that the electrical properties of suspensions are usually caused by several types of charge carriers and depend a lot on the measurement conditions, in particular, the type (constant or alternating) and frequency of the electric current (6)…(8) [2, 3]. A new theoretical analysis and comparison of its results (9)…(11) with experimental data to determine the electrical properties of a water-graphite suspension (Table 1) revealed that the sensitivity of one of the impedance components (active or capacitive) to changes in a specific fluid property is higher than the total impedance. The experimental dependencies of the impedance components of a model fermented milk product on its fat content at low frequencies (up to 400 Hz) and voltage (up to 5 V) of electric current are presented (Figures 2, 3). These data confirmed the possibility of practical use of the design results for rapid quality assessment of various electrically conductive heterogeneous liquids with the necessary sensitivity and accuracy of measuring instruments.