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actuator
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The part of a limit switch that transfers the mechanical force of the moving part to the electrical contacts.
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air compressor
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A component that pressurizes ambient air and directs it into a pneumatic system.
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automatic input
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A type of control device that is set to automatically control each step in a process. Pressure switches, flow switches, and temperature switches are types of automatic inputs.
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bellows
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A cylindrical device with several deep folds that expand or contract in response to pressure. Bellows are usually used at medium pressure.
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bimetallic sensor
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A sensor with two unlike metals bonded together. The metals expand at different rates when heated, providing a physical signal that the sensor converts into an electrical signal.
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capacitive proximity switches
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Switches that are triggered when they detect either conductive or nonconductive substances.
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capillary tube sensor
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A sensor that changes internal pressure when temperature changes. Capillary tube sensors use temperature sensitive liquid.
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chatter
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The occasional unwanted vibration between components. Chatter decreases productivity and can cause wear.
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cold junction
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The end of a thermocouple that provides a reference point. The cold junction is held at a constant temperature.
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contact
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A conductive part in an electrical circuit attached to a switch that opens or closes a circuit by coming in contact with or separating from the main conductor.
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contact block
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The part of a pushbutton that holds the contacts and is activated when the pushbutton is pressed. The most common pushbutton contact block has one NO and one NC contact.
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contactor
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A device that uses a small control current to energize or de-energize a load.
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control device
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Any input device that controls the flow of current in a circuit. Control devices determine when loads are energized or de-energized.
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control relay
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An electrical switch that opens and closes a circuit. Relays can open or close one or many sets of contacts.
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deadband pressure
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The amount of pressure that must be removed before pressure switch contacts reset after the actuation level has been reached. Deadband pressure is also referred to as differential pressure.
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diaphragm
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A deflecting mechanism that moves when reacting to pressure. Diaphragms are usually used at low pressure.
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eddy current
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A magnetic current created by sensor vibration that flows out and around the sensor head.
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electrical devices
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A type of control device that senses the presence of an object without touching it. Electrical devices include proximity switches and photoelectric switches.
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extended button operator
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A type of pushbutton operator that extends beyond the guard ring. An extended button operator is used when accidental startup is not hazardous.
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float
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A device used in switches that floats on liquid. The float raises or lowers based on the level of the liquid.
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flow switches
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Switches that detect the movement of any fluid, such as liquid, gas, or air in a system. Flow switches are commonly used in fluid pumps and air compressors.
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fluid pump
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A mechanical device used to move liquids in a hydraulic system.
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flush button operator
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A type of operator that has a guard ring around it to prevent accidental startup.
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fork lever actuator
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A type of actuator that is moved by one of its two roller arms. Fork lever actuators can detect movement in two directions.
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guard ring
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A device around a pushbutton operator that prevents an individual from accidentally pressing the button.
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hot junction
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The end of a thermocouple the measures temperature. The hot junction is exposed to the elements.
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hydraulic
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Power created by the motion and pressure of fluids.
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inductive proximity switches
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Switches that are triggered when they detect a conductive substance.
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legend plate
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The part of a switch that has the written function of the switch's operation. A legend plate often includes the words "start," "stop," "jog," "on," or "off."
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level switches
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Switches that detect the height of a liquid or solid in a tank or another type of vessel. The most common type of level switch is the mechanical level switch.
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lever actuator
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A type of actuator that works through a lever connected to the shaft of a limit switch.
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light source
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A beam of light received by a photosensor used to trigger photoelectric switches.
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limit switches
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Switches that detect the presence or absence of an object by physically touching it. Limit switches have a variety of actuators that come into contact with an object.
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main control station
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A control panel on a machine that consists of the main pushbuttons and switches that turn the machine on and off and control various other functions.
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manual input
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A type of control device that requires an individual to manually press a button or turn a switch. Pushbuttons and selector switches are types of manual inputs.
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mechanical devices
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A type of control device that physically contacts an object. Mechanical devices include limit switches, flow switches, and level switches.
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mechanical input
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A type of control device that must touch an object in order to detect it. A limit switch is a type of mechanical input.
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mechanical level switch
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A type of level switch that uses a float that triggers electrical contacts when the liquid reaches a set height.
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motor starter
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An electrically operated switch that uses magnetic induction to provide the startup current for a motor.
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mushroom button operator
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A type of pushbutton operator that hangs over the guard in a mushroom shape. A mushroom button operator is easy to press and is used for emergency stops.
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operator
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The part of a switch that is pressed, pulled, or turned by an individual operating the circuit. Operators come in a variety of styles and sizes.
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paddle
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A hinged actuator used in many types of flow switches. The flow of fluid deflects the paddle, actuating the flow switch contacts.
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photoelectric switches
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Switches that use a light beam to detect the presence of an object without touching it. Photoelectric switches can detect light objects, heavy objects, or objects that are too hot.
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photosensor
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A type of sensor that detects the presence of an object through the use of a beam of light.
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piston
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A rod inside a cylinder that is moved by hydraulic or pneumatic pressure. Pistons are used at high pressure.
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pneumatic
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Power created by the motion and control of gas, often air, under pressure.
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pressure
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The amount of force exerted on a surface divided by the area of the surface. Pressure is typically expressed in pounds per square inch (psi).
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pressure switches
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Switches that detect a certain amount of force and activate electrical contacts when the force is reached. Pressure switches have different sensing devices that detect pressure changes.
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proximity switches
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Switches that use an electronic sensing field to sense the presence of an object without touching it. Proximity switches can detect the presence of almost any liquid or solid.
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push roller actuator
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A type of actuator that moves directly forward into the limit switch.
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pushbutton
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A manual control device that opens or closes a circuit when pressed. Pushbuttons can be normally open or normally closed.
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relay
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An electrical switch that opens and closes a circuit. Relays can open or close one or many sets of contacts.
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resistance
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The opposition to current flow. Electricity flows in the path of least resistance.
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resistor
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A device used in circuits to limit current flow.
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selector switches
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Switches that can be turned to different positions to make a connection with the contacts in that particular position.
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sensor
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A device that detects a change in a physical stimulus and turns it into a signal that can be measured or recorded. All sensors are control devices, but not all control devices are sensors.
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solenoid
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An output device that converts electrical energy into linear mechanical force.
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stop plate
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A metal guard plate connected to a limit switch that prevents damage to the switch. Stop plates keep limit switches from being forced beyond their travel limit.
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switch
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A device that opens and closes a circuit.
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temperature switches
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Switches that react to different heat intensities and activate electrical contacts when the temperature rises or drops below a set level. Temperature switches are often used in heating and cooling systems.
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thermistor
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A resistor that is temperature sensitive. As temperature changes, the resistance of a thermistor changes.
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thermocouple
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A temperature sensor that measures heat at a hot junction and outputs voltage at a cold junction. Thermocouples output voltage that is proportional to the measured temperature.
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three-position selector
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A selector switch that allows you to select one of three circuit conditions. The third position is usually OFF, as in forward/reverse/off.
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two-position selector
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A selector switch that allows you to select one of two circuit conditions. Common two-position selector switches are on/off and forward/reverse.
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wobble stick actuator
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A type of actuator that works through any movement into the switch except a direct pull.
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