Automotive internal combustion engines use level sensors to monitor the amount of fuel in the fuel tank. Some vehicles use level sensors to determine when they are flowing: fewer and fewer cleaning fluids, coolants, and brake fluids. Some level sensors use floats up and down on the surface of the liquid and use position sensors to produce an output about the position of the float.
Another popular technique is to detect the fluid level by monitoring the insertion of a rod-like capacitor in the fluid; as more and more fluid surrounds the rod, the capacitance increases. The ultrasonic level sensor works like a distance sensor that monitors the distance between the tank wall and the liquid surface. Optical sensors can be used in fluids that isolate the environment. In these types of sensors, the light generated by the laser or light-emitting diode is detected at the opposite end of the fluid tank, and the amount of light reaching the sensor is inversely proportional to the amount of fluid in the tank.
Float level switch
The sensor uses a magnetic float and liquid surface movement to actuate a sealed "reed switch" in the channel. This simple and relatively low maintenance design is easy to install and minimizes shock, vibration, pressure and various fluid products
Non-contact ultrasonic sensor
These liquid level sensors use ultrasonic distance sensors to measure the distance from the surface to the top of the tank.
Contact ultrasonic sensor
These sensors use a low energy ultrasonic device that measures the presence or absence of liquid at the target point. When the fluid is in contact with the sensor, the ultrasonic signal decays, which triggers a relay.
Capacitive liquid level sensor
When the capacitive sensor senses fluid between two conductors, the capacitance changes. The same is true for ultrasonic sensors. There are capacitive sensors that contact, detect the presence or absence of fluid at one point, and there are also non-contact level sensors that detect the amount of change in fluid level as the amount of change in capacitance determines the fluid flow between the plates.