A level sensor system for liquids and liquid slurries utilizes a capacitive probe which extends longitudinally into a liquid or liquid slurry containing vessel, and which may contain inner and outer sensors spaced from each other in an assembly with a flow control screen at its lower end to permit egress...http://www.google.es/patents/US4888989?utm_source=gb-gplus-sharePatente US4888989 - Level sensor system
