Fuel level sensor is usually composed of three parts: a sensitive element, a conversion element and a measuring circuit. 1. The sensitive element refers to the part that can directly feel (or respond) to be measured. The sensitive element that is measured through the sensor is converted into non-electric quantity or other quantity that has a definite relationship with the measured. 2. Conversion elements convert the above non-electric quantity into electrical parameters. 3. The function of the measuring circuit is to convert the input electrical parameters of the conversion element into voltage, current or frequency and other measurable electric quantity for display, recording, control and processing.