10. Electrical conductivity or resistivity measurement systems

10.1 Method principle and applications

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...