The Boeing Company
Fuel level measurement using in-tank measuring system

Abstract:

An apparatus for measuring the level of fuel in a fuel tank is disclosed. The apparatus comprises an in-tank measuring system that provides an oscillating output signal generated, for example, by an oscillator such as a multivibrator, where the oscillating output signal has a frequency corresponding to the fuel level. The in-tank measuring system includes a capacitive fuel probe mounted within the fuel tank to contact the fuel. The fuel probe has a capacitance that is a function of the level of the fuel. The oscillator is configured for mounting within the fuel tank at a position in close proximity to the capacitive fuel probe. The oscillator circuit uses the capacitance of the fuel probe to generate the oscillating output signal. A communication path communicates the oscillating output signal from the clock circuit to a circuit exterior to the fuel tank.