How do reed switches work?

Answer 1

Reed switches work on a basic principle whereby the reed switch is a hermetically sealed glass tube containing two ferromagnetic reeds that will actuate when in the presence of a magnetic field. The magnetic field may be generated from a ferrous metal such as iron, a permanent magnet such as rare earth types and/or an electromagnetic coil as used in a reed relay.

Reed switches have various electrical properties such as their sensitivity range which is generally specified in ampere turns (AT). The AT or sensitivity of the reed switch refers to the open and close points of the switch.

When a reed switch is used in conjunction with a permanent magnet, it referred to as a reed sensor. Typically the reed switch is mounted to a fixed object and the magnet to the moving object. The strength of the magnetic field as well as the position and movement of the magnet relative to the switch will determine how many open and closure points will take place.

Example: Parallel movement of the magnet to the switch can produce either one or three switch closures depending on its distance from the switch.

Answer 2

Reed switches consist of two thin, magnetizable metal reed elements sealed in a glass tube. When a magnetic field is applied, the reeds are drawn together to make contact and complete an electrical circuit. When the magnetic field is removed, the reeds return to their original position and the circuit is opened. Reed switches are commonly used in sensors and proximity sensors.