A system for detecting the presence of water in an aircraft fuel sump with the aid of a pair of electrodes to which a detector circuit is connected. When both electrodes touch water in the sump below the fuel the detector circuit energizes a warning signal. The electrodes are connected to the opposite...http://www.google.de/patents/US3950740?utm_source=gb-gplus-sharePatent US3950740 - Sump water detector with isolated probe having AC applied to its electrodes
