Electrical conductivity or resistivity measurement systems
Level Measurement and verification – systems for liquids and solids

The principle consists in measuring the electric current flowing between two electrodes, or between an electrode and the metallic mass of a tank, when the product, necessarily conductive, touches and closes the circuit. Gases or vapors are insulating at normal operating temperatures. The amplified current is used to operate a threshold relay. With rare exceptions, this method is reserved for the detection of one or more thresholds.

High-purity water has a conductivity of less than 0.05 µS.cm^–1, but it can still be detected with high-performance, expensive conductivity meters whose use for this application, except in special cases, is questionable. Hydrocarbons, like many organic products, are highly insulating. The method is of interest...