They use a buoyant float to gauge a fluid level. In most models, the float carries permanent magnets and encircles a stationary stem. As the float rises or drops with fluid level, the magnetic field ...
A few months ago, I wrote about a very popular cable float switch for another site (https://www.codrey.com/electronics/cable-float-level-sensor-switch-first-look ...
There are many different types of switches that are intended to address different design requirements, deployment environments, and usage scenarios. I’m always amazed how one thing leads to another.