Switches

Switches change contact state when the monitored variable crosses a set threshold, giving the controller a binary present/absent signal. Unlike sensors they produce a decision rather than an analogue value, which is why they are widely used in safety circuits and simple control logic. The category includes mechanical and magnetic limit switches, pressure switches, flow and level switches, and temperature switches. Selection should consider switching threshold, contact arrangement (NO/NC, single or double pole), current and voltage rating, connection type and ingress protection rating.