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 ...

This file type includes high resolution graphics and schematics. Conventional magnetic reed relays provide excellent low-power characteristics combined with a low level of electrostatic discharge (ESD ...

All credit to Thomas Langewouters for an unusual reed switch ladder circuit for liquid level sensing. You can find it on his website here. He went on to use a more traditional two-terminal design, but ...