Design of embedded fuel sensor based on intrinsically-safe circuit

The accurate measurement of fuel level plays a significant role in the cruise time and safety performance of aircraft. Capacitive sensors are currently used to measure fuel level in many aircrafts. In order to reduce the wall destruction of fuel tank and solve the problem of intrinsically safety, researchers introduce a new capacitive sensor, based on measurement principle of coaxial capacitor, to detect liquid level. This article focuses on the design of integrated structure and the intrinsically safe circuit with digital signal output. The maximum operating current is less than 50mA, which meet the requirements of current stipulated by Federal Aviation Administration (FAA) in 2008. In addition, the results of computer simulation show that the error of measurement is less than 1% and the output capacitance value has a good linear relation with the input capacitance value, which meets the design requirement.