Apparatus for detecting the presence of water in a fuel tank

Claim 1

Apparatus for determining the fuel level in a fuel tank and for detecting the presence of water in the fuel tank before such water can effect the accuracy of the fuel level determination comprising: means for generating a first AC signal; a first electrode coupled to said first AC signal generating means and operatively positioned relative to said fuel tank for coupling said first AC signal into a fluid in said fuel tank; a second electrode positioned in parallel, horizontally-spaced relationship to said first electrode whereby the capacitance between said first and second electrodes increases as the fuel level in said tank increases; circuit means coupled to said second electrode and responsive to the change in capacitance between said first and second electrodes for providing a second signal indicative of the fuel level in said tank; a third electrode operatively positioned adjacent the bottom of said tank and positioned to sense the presence of water therein; means coupled to said third electrode for providing a third signal, a characteristic of which is proportional to the amount of electrical signal coupled between said first and third electrodes; and means responsive to said third signal for indicating the presence of water in said tank when said characteristic of said third signal exceeds a predetermined value.