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Distributed Control Systems (DCS) have been the primary solution for process automation but now many PLC vendors are pursuing these applications arguing that a single integrated architecture based on PLCs and/or PACs (Programmable Automation Controllers) is the best approach to total plant automation. What is your opinion on this topic?
DCS is also a PLC which is used to control the complex batch process, which controls large distributed process ip/op by controlling from one place. In Industries Machine critical process is used where Large Digital I/O & Limited Analog I/O.
DCS have several thousands of I/Os (Input/Outputs) and use for controlling all over big plant control section in one control room operator through the use of many PLCS and their interconnection with other devices through the use of communication media(Control net ,different buses,LANs etc) and different channels assign to each section(mostly uses serial communication between them).
PLC are mostly have less I/Os(Input/Outputs) and mostly use in small batch or control process according to their I/Os size.
PLC-Programmimng logic Controller is used for controlling and monitoring high speed process parameters in a factory automation structure but they cannot use complex structures because of the restriction of the number of input devices.But then Distributed Control System (DCS) is mostly suitable for complex systems where more than one input devices is used.thats why its better to put a PLC and DCS for a large production plant for safety and save a lot of money for company...
PLCs is the best contro for automatic process.
PLC is programable logic controler and DCS is part of SCADA system of supervision
Programmable logic controllers are used for control an d monitoring of batch process with limited input/output configuration
DCS is belongs to basic process control system with high number of input/output looping facility to control continuous process with less probability of failure and criticality
In PLC system single logic gate is used to control the process but in DCS the programm is desinged as to use the logic gate as well as to take corrective measures.
control system of a plant or some kind of processorts
Plcs and DCS can be differntiated in terms of number of inputs and scanning time. therfore if i wanted to process large number of dedicated signals, irrespective of its position in the program, i should go for DCS, eg: ML-50 of honeywell has a constant scan time of 160ns and can process upto 99000 signals which is an ideal choice for power stations and recieving stations.
but in case of process based industries like bottle filling and other material handling industries, a modular plc can do a fine job.
yes PLC's can be changed around quickly to do different functions without much rewiring but if any breakdowns occur its costly to replace, and PLC gets outdated very quickly
In short words: DCS is usually used when large number of I/O is processed, large number of control loops present, and more communication is needed.
