The working principle of the automobile fuel gauge is as follows: a float is installed in the fuel tank. As the fuel is reduced, the float floating on the fuel liquid surface will also descend, thereby driving the indicator of the fuel gauge to display the fuel inventory.

The action of the fuel gauge pointer is controlled by the amount of current through the variable resistor. When the fuel tank is full, the float-metal rod-wiper makes the resistance of the variable resistor low, the amount of current that the switch is turned on is large, the pointer of the fuel gauge jumps high, and when the fuel tank is empty, the float - The metal rod-wiper makes the resistance of the variable resistor high, the amount of current that is turned on is small, and the pointer of the fuel gauge turns low.