Investigation of conductivity effects on capacitance measurements of water liquids using a cylindrical capacitive sensor

In this study by using a Cylindrical Capacitive Sensor (CCS), the Electrical Conductivity (EC), effects on the capacitance measurements of the water liquids was investigated. Theoretical values of the capacitance measurements of water liquids with the cylindrical length in the range 0.5-5 cm are calculated. Our obtained results indicate that measured capacitance value by CCS depends on the liquid capacitance and reactance capacitance. Liquid capacitance value of the distilled water for permittivity of 80 is about 33.5 pF and reactance capacitance value is about 0.290 μF, when the cylindrical length value is about 1.6 cm. The reactance capacitance for the mineral, tap and dilute salt water liquids are also investigated in this study. The reactance capacitance value of 22.80 μF for the mineral water, 37.50 μF for the tap water and 47.80 μF for the dilute salt water obtained when the cylindrical length value is about 1.6 cm. A comparison of our obtained result indicated the liquid capacitance value in the capacitance measurement is negligible. A comparison of the theoretical and experimental values shows that theoretical values are smaller than the experimentally measured values that due to the stray capacitances. The minimum error is about 3.3% for distilled water and maximum error is about 12.9% for salt water. Hence, the reported CCS provides a high sensitivity to determine the reactance capacitance value for the different water liquids with low EC. © 2010 Asian Network for Scientific Information.