Programmable Logic Controller

programmable logic controller

[prō′gram·ə·bəl ¦läj·ik kən‚trōl·ər]

(control systems)

programmable controller

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

Programmable Logic Controller

(hardware)

(PLC) A device used to automate monitoring and control of industrial plant. Can be used stand-alone or in conjunction with a SCADA or other system.

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PLC

(1) (Power Line Communications) See broadband over power lines.

(2) (Programmable Logic Controller) A programmable microprocessor-based device that is used in discrete manufacturing to control assembly lines and machinery on the shop floor as well as many other types of mechanical, electrical and electronic equipment in a plant. Typically RISC based and programmed in an IEC 61131 programming language, a PLC is designed for real-time use in rugged, industrial environments. Connected to sensors and actuators, PLCs are categorized by the number and type of I/O ports they provide and by their I/O scan rate.

In the late 1960s, PLCs were first used to replace the hardwired networks of relays and timers in automobile assembly lines, which were partially automated at that time. The programmability of the PLC enabled changes to be effected considerably faster. Contrast with PAC and DCS. See IEC 61131.

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