The Sensor is operated by a self-elastic diaphragm or movable diaphragm with fitted hairspring, whose position is determined by the pressure applied to it.
When the water hits the rotating impeller, energy of the impeller is transferred to the water, forcing the water out (centrifugal force).
The base holds the other parts, and the spring keeps the belt pulled tight. The pulley is what facilitates movement of the belt.
Oil level sensors use magnetic reed switches, that are hermitically sealed in a stainless steel or plastic stem, to measure oil levels and automatically turn on or off oil pumps.