The below given table gives the difference between PLC and DCS Systems.
The main difference between Programmable Logic Controller (PLC) and Distributed Control System (DCS) are:
The number of I/O in the system. DCS is dealing with very large no. of I/O with less cost. also DCS comes with it’s SCADA always. if DCS stopped, all system is stopped. if the system has less No. of I/O, then PLC is better from cost view. Also SCADA is optional. if system is controlled by no of PLC. if PLC is down. others continue working Normally. Historical, main difference was that DCS deal with Analogue signals but PLC deal with Discrete digital system. Now DCS has Digital Modules and PLC has Analogue modules.
Besides, PLC has a processor and input and output cards (I/O card could be digital and/ or analog) Processor has the software - basis the input it receives from field devices it gives out the output commands to control devices of the field. DCS is a group of individual smart controllers (again having embedded software and connections with field devices) doing their specified operation (duty) but interconnected.
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