What makes a programmable logic controller (PLC) different from a typical computer? After all, computers are used to control things; they can even run a software PLC.
So what exactly is a PLC? A PLC is a digital computer used to control electromechanical processes, usually in an industrial environment. It performs both discrete and continuous control functions and differs from a typical computer in several important ways:
Also, unlike computers, PLCs are made to run 24/7 and are designed to resist harsh physical and electrical environments.
Where are PLCs used? PLCs are used in many different kinds of applications and industries. In a 2012 Control Engineering magazine poll, 87% of machine control applications used a PLC as the control platform. This includes assembly, packaging and other manufacturing operations. 58% of process control applications used PLCs, in such industries as chemical processing and the oil and gas industry. Power plants and wastewater treatment also fall into this category. 40% of motion control and robotics, 26% of batch control and 18% of diagnostic or testing applications used PLCs.
Many applications are a combination of these, which just goes to show that PLCs are used anywhere and everywhere.
Frank Lamb is the founder of Automation Consulting Services Inc. This article originally appeared on the Automation Primer blog. Automation Primer is a CFE Media content partner. Edited by Chris Vavra, production editor, Control Engineering, CFE Media, cvavra(at)cfemedia.com.
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