Inductive-Capacitive Coupled Probe for Non-Contact Measurement of Liquid Conductivity

This paper presents a non-contact inductive and capacitive coupled method of measurement of conductivity of liquids. The current through a pre-set column of liquid is established through induction. The voltage drop across the preset column of liquid is measured through capacitive coupled electrodes. The absence of contacting electrodes ensures that the method is free from effects due to contamination / corrosion of electrodes. The method proposed ensures that the measurement of the voltage drop across the column is independent of the values of the coupling capacitances of the capacitive coupled electrode. Hence, any deviation in the fabrication of the probe has negligible influence on the measured conductivity. Results obtained from a prototype unit built and tested show that the maximum relative error in the conductivity measurement is lt; \mathbf{0.82}\ \%$ and the measured conductivity values are independent of the values of the coupling capacitors.