Fluid Level Sensors

Basic Description

Automobiles with an internal combustion engine use a fluid level sensor to monitor the amount of gasoline in the fuel tank. Some vehicles use fluid level sensors to determine when fluids such as washer fluid, coolant or brake fluid are getting low. Some fluid level sensors employ floats that move up and down with the fluid surface and use position sensors to produce an output relating to the position of the float. Another popular technique for detecting fluid levels is to monitor the capacitance of a rod inserted in the fluid. As more fluid surrounds the rod, the capacitance increases. Ultrasonic fluid level sensors work like acoustic distance sensors that monitor the distance between the tank wall and the fluid surface. In fluids that must be isolated from the surrounding environment, optical sensors can be used. In these types of sensors, a laser or LED produces light that is detected on the opposite end of the fluid tank. The amount of light reaching the sensor is inversely proportional to the amount of fluid in the tank.

Different methods for measuring fluid levels in a tank.

Manufacturers

ABB, Continental, Deeter, Denso, Electrosense, Fluid Switch, Gems, Gill, Honeywell, PKP, SensorTechnics, Siemens, SSI

For More Information

[1] A Dozen Ways to Measure Fluid Level and How They Work, Sensors Magazine, Dec. 1, 2004.

[2] Measuring Liquid Level in a Sealed Tank with a Hydrostatic Pressure Sensor, SensorsOne.co.uk, Jan. 6, 2008.