Page 31 - AUTOMATION EISBN

TOPIC 3 : INPUTS AND OUTPUTS OF A PLC

3.1 Types of Input to a PLC

Digital Input Analog Input

Digital inputs are simply two states, Analog inputs are thoselike
likethose of a switch position temperature and pressure which

indicating as On or Off span over a range of values

Digital Inputs include push-buttons, Analog Inputs include
limit switches, relay contacts,
temperature
proximity switches, photo sensors
(On/Off), pressure switches and sensors/transmitters, current
more. sensors, voltagesensors and
others that can convert a physical

quantity to an electrical signal.

Digital inputs devices are available in
both DC as well as AC and some are
voltage independent such as a switch

contact.

3.1.1 Input Device

• Push buttons.

• Selector Switch

• Limit Switches

• Through Beam Sensor

• Inductive Proximity Sensor

• Capacitive Proximity Sensor

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