An instrument for measuring the amount of oil by changing the capacitance of the capacitor and the liquid level of the oil tank. It consists of capacitance sensor and servo indication system. The sensor is a capacitor composed of several concentric cylindrical plates, which is inserted vertically into the fuel tank. The dielectric coefficient of fuel is greater than that of air. When the fuel height in the fuel tank changes, the capacitance changes accordingly, which is converted into corresponding electrical signals by the servo indication system to indicate the corresponding fuel value.

Capacitive oil gauge is a kind of electromechanical instrument. It is an instrument commonly used in the army at present. The sensor is a cylindrical capacitor composed of concentric cylindrical plates. This principle is based on the single-valued functional relationship between the capacitance of cylindrical capacitor and the oil level height. Then, the capacitance corresponding to the oil amount is converted into the rotation angle of the pointer by the self-balancing measuring circuit. The self-balancing measuring circuit consists of resistance-capacitance bridge, transistor amplifier, two-phase asynchronous motor, reducer, dial and pointer.

The basic working process of the fuel meter is as follows: firstly, the fuel level, flight attitude and mathematical model stored in the fuel tank are measured by the fuel measuring sensor, and the corresponding fuel quantity is calculated. Then, by combining the fuel densities measured by the fuel density sensor, the fuel quality in the fuel tank can be obtained. The fuel measurement task computer transmits the fuel quality to the cockpit display system and the flight management task system through the data bus.