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Proximity switches operate by the disturbance of an electromagnetic field, by capacitance, or by sensing a magnetic field. Rarely, a final operating device such as a lamp or solenoid valve is directly controlled by the contacts of an industrial limit switch, but more typically the limit switch is wired through a control relay, a motor contactor ...
Zero speed switches (ZSS) also known as Speed Actuating Sensing Switches [1] are used to detect whether a rotating shaft is turning (even at very slow speeds) [2] in various machines, conveyors, power plants, and in industries involving the production of cement, sugar, textiles, paper, etc. Zero speed switches mainly use electromechanical, electronic, or magnetic proximity technologies.
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 ...
An infrared proximity sensor Optical proximity sensor in a 2016 Samsung smartphone.A proximity sensor is a standard feature of most smartphones, disabling the touchscreen when positioned near an ear during phone calls; more recent (late 2019-early 2020) smartphones with OLED displays may have the sensor mounted under the display.
The hysteresis thresholds for switching (specified as B OP and B RP) categorize digital Hall ICs as either unipolar switches, [9] omnipolar switches, [10] or bipolar switches, [11] which may sometimes be called latches. [12] Unipolar (e.g., A3144) [13] refers to having switching thresholds in only one polarity of the magnetic field. Omnipolar ...
A reed switch has very low resistance when closed, typically as low as 0.05 ohms, whereas the Hall effect sensors can be in the hundreds of ohms. A reed switch requires only two wires whereas most solid-state devices require three wires. A reed switch can be said to require zero power to operate it.
A VR sensor used as a simple proximity sensor can determine the position of a mechanical link in a piece of industrial equipment. A crankshaft position sensor (in an automobile engine) is used to provide the angular position of the crankshaft to the engine control unit. The engine control unit can then calculate engine speed (angular velocity).
Since the output of an inductive sensor has two possible states, an inductive sensor is sometimes referred to as an inductive proximity switch. [2] [3] The sensor consists of an induction loop or detector coil. Most often this is physically a number of turns of insulated magnet wire wound around a high magnetic permeability core, such as a ...