PLC vs DCS (Difference between PLC and DCS)

PLC vs DCS :

Market Intorduction 1960’s 1970
Replacement of…. Electromechanical Relays Pneumatic & Single-Loop Controllers
Products Manufactured… “Things” “Stuff”
Classic Application Automotive Refining
Type of Control Discrete Regulatory
Redundancy “Warm” Backup “Hot” Backup
Engineering Mindset “Programming” “Configuration”
Operator interaction Exception Basis Man in the Loop
Operator interaction Exception Graphics Sophisticated Graphics
Size/Foodprint Compact Large
Up-front cost $$ $$$$
System “open” “Closed (proprietary)”
Programming Language High level programming languages are available for creating custom logic Custom logic created from existing function blocks
Algorithms Customized routines usually required- Many algorithms (i.e. PID) are complex and do not vary among application
Standard libraries Standard libraries considered nice features Standard application libraries are expected (function blocks and faceplates)
Solutions Provisions must be available to integrate functions/ products into an integrated architecture Entire system is expected to function as a Complete solution
Redudancy Redundancy may not be cost justified System redundancy is often required
Analog Control Analog Control: Simple PID only Analog Control: Simple to advanced PID control up to Advanced Process Control
Diagnostics Diagnostics to tell you when something is broken Asset Management alerts you to what migh break before it does
Design System
designed to be flexible
System designed to make it”easy” to engineer process applications

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