Fuel level sensors, also known as fuel gauges, allow drivers to monitor fuel consumption and help them to determine when to refill the tank. They consist of two main components: the sensing system itself (also known as the sender) and the indicator (also commonly referred to as the gauge).
Some smaller aircraft use the same sensing mechanisms as automobiles in their fuel level sensors; however, in larger aircraft, a number of sensors are used to cover the increased size of the fuel tank. It is imperative for aircraft to avoid the inaccuracies present in some automotive fuel level sensors, as the stakes are much higher—loss of fuel could have catastrophic consequences. Additionally, sensors used in aircraft must be able to cope with changes in altitude; therefore, they are more sophisticated than automotive ultrasonic fuel level sensors. Aircraft typically rely on either ultrasonic or capacitance sensors.
Ultrasonic sensors measure the height of the fuel in the tank by sending out ultrasonic signals, which are measured on the other side of the tank via another sensor. On the other hand, when capacitance sensors with driver fatigue monitor are used, the fuel passes through special vents when it consumed, causing the capacitance to change in the sensors, enabling the level of the fuel in the tank to be determined. This information is then passed on to the pilots via the onboard computing system.
The level fleet management sensor in a vehicle’s fuel tank is actually a combination of three components; a float, an actuating rod and a resistor. This combination of components sends a variable signal to the fuel gauge or an electronic device -- a “little black box” -- that actuates the fuel gauge. The sensor assembly is often referred to as a sender. It is a relatively simple system once the function of each component part understood.
How It Works
Inside the resistor, a device with personal tracker that resembles a tiny windshield wiper is moved over a strip of resistive material by the movement of the actuating rod. The farther along that strip from the grounded end of the resistant strip the wiper is, the less electricity is conducted to it by that material. The wiper is oriented so the most resistance is encountered when the tank is at its emptiest, and the least when the tank is full. The maximum signal -- the unmodified 12-volt current -- makes the needle in the fuel gauge swing over to “full.” As the fuel level decreases the float drops, the actuator rod causes the wiper to move across the resistant strip away from the ground, and less current is passed to the gauge. The needle shows a decreasing reading. When the tank is empty, the float is at its lowest and the wiper is at the far end of the resistant strip from the ground, so very little current is sent to the gauge. The needle doesn’t move far, thus reads “empty.”