Contactless measurement of liquid surface level - utilises capacitor electrode to provide control signal for motorised probe movement

摘要

The measurement and control of the face surface of a liquid or the separation surface between two liquids is performed without requiring contact. This allows measurements to be made on fusing metals or between water and hydrocarbons. A flat electrode (E) is electrically isolated and forms a capacitor with the surface (S) of a conducting liquid. The capacitor is connected to a capacitance meter (P) which compares the value with a demand value (V). The error signal is used to control a motorised movement system (M) for the electrode. This allows the level of the surface to be controlled via electric or pneumatic systems which also provide information. The hyperbolic law of capacitance against separation (e) of electrode from the surface can be corrected by an electronic circuit.