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 ...

They do so by sending a small current through their probe tip. Current flowing between the sensor and some reference (often the metal tank holding the liquid) is compared inside the sensor to current ...

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.