Development and construction of a cost-effective non-contact instrument for measuring the dielectric constant of liquids.

This article focuses on the development of a cost-effective, non-contact instrument designed to measure the dielectric constant of pure liquids and solvent mixtures by detecting changes in capacitance and relaxation frequency using an astable multi-vibrator circuit. The device employs a measurement cell with a removable glass test tube between aluminum plates, allowing frequency changes to be correlated with dielectric constants through an empirically derived calibration curve. Testing demonstrated high frequency stability and accuracy, with results for various solvent mixtures closely matching experimental data and outperforming several computational models in mean relative deviation. The apparatus's non-contact design enables measurement of conductive and corrosive liquids without expensive electrodes, making it suitable for laboratory, industrial, and educational applications requiring rapid, reliable dielectric constant determination.