There are three typical liquid level sensing approaches. One approach uses inductance to sense motion, the second uses a direct connection from a float that mechanically moves a contact switch, and the third approach uses a float with an embedded magnet that activates a reed switch. The inductive approach is expensive and requires a lot of circuitry. The mechanical approach can easily get clogged and is subject to failure in dirty environments. For these reasons this presentation will focus on the reed sensor technology, which is being implemented in many applications.