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Magnetic switch. Magnetic switch is an electrical switch that makes or breaks contact in the presence of a magnetic field.Applications include situations where it is not desirable or possible for moving elements to make direct contact with the switch, such as in explosive environments, submerged in liquids, and where repetitive contact with a mechanical switch would result in undesired wear.
A magnetic switchable device (often called a magnetic base) is a magnetic fixture that uses one or more permanent magnets in a configuration that allows the external field to be turned on or off. They are used in many applications including optics , metalworking , lifting , and robotics, to attach items to metal surfaces in a secure but ...
Switches can be designed to respond to any type of mechanical stimulus: for example, vibration (the trembler switch), tilt, air pressure, fluid level (a float switch), the turning of a key , linear or rotary movement (a limit switch or microswitch), or presence of a magnetic field (the reed switch). Many switches are operated automatically by ...
(from top) Single-pole reed switch, four-pole reed switch and single-pole reed relay. Scale in centimeters. A reed relay [i] is a type of relay that uses an electromagnet to control one or more reed switches. The contacts are of magnetic material and the
1835 – Joseph Henry invents the electric relay, which is an electrical switch by which the change of a weak current through the windings of an electromagnet will attract an armature to open or close the switch. Because this can control (by opening or closing) another, much higher-power, circuit, it is in a broad sense a form of electrical ...
The thermal and magnetic overload detections are typically used together in a motor protection relay. [citation needed] Electronic overload protection relays measure motor current and can estimate motor winding temperature using a "thermal model" of the motor armature system that can be set to provide more accurate motor protection.
The reed switch [i] is an electromechanical switch operated by an applied magnetic field. It was invented in 1922 by professor Valentin Kovalenkov at the Petrograd Electrotechnical University , [ 1 ] and later evolved at Bell Telephone Laboratories in 1936 by Walter B. Ellwood into the reed relay.
The most widely used electronic switch in digital circuits is the metal–oxide–semiconductor field-effect transistor (MOSFET). [2] The analogue switch uses two MOSFET transistors in a transmission gate arrangement as a switch that works much like a relay, with some advantages and several limitations compared to an electromechanical relay.