Answer / jain

PLC is controlling only one process unit with one CPU.
DCS can control many process units with many CPU.

Answer / rizvi

Plc is a programmble logic control device which has no.of CPU
where as a Distributed Control System

Answer / jitendra chauhan

PLC is a single digital module which is stand with on/off
digital input/output,PLC ahd seprate a single logic,used
for single particuler performing complete the task of
operation. And DCS is a combination of PLC which made a
joined a network through controlled and operation on a
single controlled room.

Answer / pranab nath

DCS is useful only for process control loop as compare to
PLC

Where as PLC can perform high speed discrete control,
motion control and process control also.

Answer / ravi kant anand

There is a chip inside PLC which is burnt with logics as
per requirement of process and once the chip is burnt after
that you can only modify the logic or even you can include
single I/O by reburning the chip only in shutdown of
process "not in running process",second option could be to
include separate PLC for including even single signal in
running process. but in case of dcs you can include, modify
or change the logics, even in running process by
downloading into controller.
finally we can say, it would be better
to use PLC if you are quite sure that there would not be
any inclusion, modification or change in logic for the
process otherwise DCS would be smart choice.
generally for small process we could
be sure that there would not be any inclusion, modification
or change in logic for the process so most often we use
PLC, but for large process like handeling the process of
whole power plant, logic inclusion, modification or change
is often so dcs would be better choice.

Answer / veeru

The simple difference of the PLC is open loop system and where the DCS is Closed loop system

Answer / sara

Dcs is the advanced method of plc. It is the graphical representation of process.plc cannot monitor the process which is going.

Answer / pranav

the difference between plc and dcs is in their scan time.
scan time of plc is less than that of dcs.

Answer / rajaram

NOW DAYS THERE ARE NO MORE DIFFERENCE IN PLC & DCS,
BASICALLY PLC ARE USED REDUCED NO OF ELECROMAGNETIC RELAY &
dcs IS USED FOR REDUCED pid CONTROLLER.
NOWDAYS PLC ARE SUING FOR SEQUENCIAL CONRROL I.E ESD AND
OTHER SAFETY RELATED SPECIFIC SYATEM OND OTER HAD DCS IS
BEING USED FOR CONROL OVER ALL PLANT AT ONE PLACE USING V
NET(YOKOGWA SYSTEM) OR DELTA v(EMERSON).
PLC TAKES LESS TIME TO CONTROL THE PROCESS MEANS CONTROL
ACTION HOWEVER IN CASE OF DCS IT TAKES MORE TIME.
IN DCS DIFFERENT PLC CAN DO COMMUNICATE EACHOTHER AND DCS
EXECUTED CONTROL ACTION BY OPERATOR THROUGH FUCNTION BLOCK
AND IN plc IT IS FERFORMED BY LADDER.
PLC ARE NOT PROPRIETARY SYSTEM HOWEVER DCS PROPRIETARY
SYSTEM .

Answer / him

well plc is for one machine control and dcs for so many
machines control with one cpu.

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