On a combustion or hybrid UAV, fuel is the endurance. The autopilot and the remote pilot need to know how much is left, how fast it is being used and whether the fuel system is working, because a fuel problem beyond line of sight leaves little time to react. Fuel sensors provide that information.
Sensor types
Capacitive level sensors: measure the fuel height from the change in capacitance between electrodes. No moving parts, accurate, and can be shaped to the tank.
Ultrasonic level sensors: measure distance to the fuel surface; non-contact.
Float and reed-switch sensors: simple, light and cheap; resolution is limited and moving parts can stick.
Fuel flow meters: turbine or other flow sensors that measure consumption; integrated over time they give fuel used.
Fuel pressure sensors: confirm pump operation and detect blockages or leaks.
Key specifications
Measurement range and accuracy, including in attitude changes: fuel moves in the tank during climbs, turns and turbulence.
Probe length and whether it can be cut or shaped for the tank.
Fuel compatibility: gasoline, heavy fuel, kerosene and biofuels.
Output: analog, frequency, CAN or serial, matched to the ECU or autopilot.
Mass, power and vibration resistance.
Intrinsic safety for use inside fuel tanks.
Getting reliable fuel data
The best estimate combines a level sensor with a flow meter: the level tells how much is in the tank, the flow tells how fast it is going, and their comparison detects leaks and sensor faults. Several level probes, or software that corrects for attitude, improve accuracy in small, irregular UAV tanks.
It has two electrodes along the probe. Fuel and air have different dielectric constants, so the capacitance changes with the fuel height. The electronics turn that change into a level reading.
Why combine a fuel level sensor with a flow meter?
The level sensor gives the quantity in the tank, but it is disturbed by fuel movement in flight. The flow meter gives consumption precisely. Comparing both improves the estimate and reveals leaks or faults.
Do fuel sensors work with heavy fuel?
Many do, but it must be checked: heavy fuel has different dielectric and chemical properties from gasoline, so capacitive sensors must be calibrated for it and materials must be compatible.
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FeaturedFuel sensors
FeaturedFuel sensors
FeaturedFuel sensors
FeaturedFuel sensors
