When measuring discrete levels of liquids, such as automobile brake fluid, reed switch technology is simple, inexpensive, and reliable. A magnet mounted on a float closes an adjacent magnetic reed switch as the magnet approaches. Typically, the reed switch is mounted in a plastic or non-magnetic metal tube, and a ring magnet mounted on a float rides up and down the tube on the liquid surface (Fig. 1). A ring magnet is a good solution since as the magnet sweeps by the reed switch....
