Abstract
Concentration measurements are important in bioethanol industries, in the R&D areas, for chemical, medical and microbiological analyses and processing as well as for diagnostics, manufacturing, etc. The overview shows development of the structural design of a system for measuring the concentration of solutions and mixtures consisting of two dielectric liquids. The basic principles of the system's design are given along with relevant equations. The concentration of dielectric liquids is measured using devices with capacitive sensors (1-300 pF). The operational frequency of the developed measuring system is 100.000 kHz. Configuration of the system excludes some errors usually arising at measurements, and broadens its applicability. For testing, the system was calibrated for measuring the concentration of anhydrous ethanol + de-ionized water mixture. Experimental results have shown a stable resolution of ±0.005 pF at measuring the sensor capacitance and a reproducible resolution better than ±0.01% at measuring the ethanol volume concentration