Answer / haridass

So many difference are there in that.
But the main difference is,

Many PLCs can be controlled through one DCS, but DCS cannot
be controlled by PLC. For the large plant DCS is the best
than PLC.

Answer / vaibhava satsangi

PLC - PROGRAMABLE LOGIC CONTROLLER
DCS - DISTRIBUTED CONTROL SYSTEM

PLC - PREFERED FOR SMALLER APPLICATIONS, DIGITAL I/OS,
DIGITAL INTERLOCKS, CAN BE USED IN REDUNDENT APPLICATIONS
IF USED FOR PROCESS CONTROL I/O ADDRESSES AND TABLES LOADED
ON A SEPRATE PC's.

DCS - PREFFERED FOR BIGGER APPLICATIONS, TO CONTROL
DIFFERENT PLANTS LOCATED AT DIFFERENT LOCATION FROM THE
CENTRLISED/LOCAL LOCATION, MAY BE CONTROLLING VARIOUS PLC's
ALSO, PREFFERD FOR PID's GROUPS, THIS A EXPENSIVE &
CRITICAL CONFIGURATION, PREFFERD TO CONTROL CRITICAL
PROCESS. I/O ADDRESSES AND TABLES LOADED WITHIN SYSTEM CAN
BE ASSESSED FROM ANY HMI(HUMAN MACHINE INTERFACE).

Answer / kuldeep

PLC having limited communication protocol while DCS having
open protocoal.

Answer / ravindraeee

dcs:(DCS) refers to a control system usually of a
manufacturing system, process or any kind of dynamic system,
in which the controller elements are not central in location
(like the brain) but are distributed throughout the system
with each component sub-system controlled by one or more
controllers. The entire system of controllers is connected
by networks for communication and monitoring.

DCS is a very broad term used in a variety of industries, to
monitor and control distributed equipment.

* Electrical power grids and electrical generation plants
* Environmental control systems
* Traffic signals
* radio signals
* Water management systems
* Oil refining plants
* Chemical plants
* Pharmaceutical manufacturing

plc:A programmable logic controller (PLC) or programmable
controller is a digital computer used for automation of
electromechanical processes, such as control of machinery on
factory assembly lines, amusement rides, or lighting
fixtures. PLCs are used in many industries and machines.
Unlike general-purpose computers, the PLC is designed for
multiple inputs and output arrangements, extended
temperature ranges, immunity to electrical noise, and
resistance to vibration and impact. Programs to control
machine operation are typically stored in battery-backed or
non-volatile memory. A PLC is an example of a real time
system since output results must be produced in response to
input conditions within a bounded time, otherwise unintended
operation will result.
so PLCs and PIDs&etc are the part of DCS and total system is
equipped with HMI and MMIs which are used monitor&control
the plant and to modifying the set point

Answer / sohail malik sngpl pakistan

there is a very important difference b/w PLC and
DCS ....Basically in a process controll system plc is
sequential bases however DCS on loop control based.
explanation if in a PLC controlled system any Intrruption
or error signal generatd the whole system which is operated
bye this PLC effected and should be stopped and give Alarm
in fact in DCS system if there is any problem generated the
system give indication such problem but switch over to the
next loop or task which may not effected.

Answer / ravindraeee

PLC=Programmable Logic Controller
DCS=Distributed Control System

A PLC can be a component of a DCS

A DCS can include Networked PLCs, PCs, or other control
equipment sharing or distributing control of a process or
processes. Key word being "distributed".

Answer / md.abdul majeed

IN PLC(PROGRAMMABLE AND LOGIC CONTROLLER)ONLY FEW ANALOG
SIGNAL ARE TESTED,WHERE ELSE USING DCS(DISTRIBUTED CONTROL
SYSTEM)WE CAN TEST MORE AND MORE ANALOG SIGNALS.

Answer / karthi

plc may use only small scale industry but dcs may use both small scale and large scale industry.

Answer / seshu

no of programes or logies is called plc and grop of plces is called dcs

Answer / anoop

DCS is redundant but PLC is not redundant.

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