Answer / binu

We can use both PLC and DCS for the same function i.e
controlling analog and digital signals.
However PLC is preferred for digital application/switching
action because the scan time is less for digital signals
compared to DCS digital cards and more for analog signals
compared to DCS.
DCS is preferred to be used for analog application as the
scan time is less compared to PLC analog cards and more for
digital compared to PLC.

Answer / ahmed bilal

PLC is programmable logic contol, while DCS is distribution
control system.
PLC is for operating certain number of devices on the basic
of analog / digital outputs. Normally the output of
industrial devices is in analog, which comes to PLC kits
where they are converted to digital with ADC than excuted
instructions according to program spscified by user. In
this wasy we can control multiple devices.

DCS is for controlling over all network. Basically many
block of PLC when optomized than the name becomes DCS

Answer / senthil

PLC - communicates fast with digital signals i.e processing
speed is high compared to DCS.
- suitable for individual systems and not for a whole plant.

DCS - the name itself says, distributed control system.the
whole unit is under control of it.it links with Time
servers,thin clients,ring topology with redundant
concepts,and many more advantages.
mail me if u need more info..

Answer / ecxlsync

with regards to their names:
PLC is just a controller and part of the DCS.
DCS is a control system network architecture which has
several PLC's in the field.

Answer / www.islamqa.com

# PLC is first invented and developed to be used with
discrete - on/off control & with small scale applications.

# DCS is designed and fabricated to handle modulating/PID
control applications & to serve in large scale I/Os
applications.

# with great progress and achievements in plc h/w and
networking technologies we have PID algorithms with PLC and
also plc become able to handle wide range of I/O'S like
DCS, actually with good engineering the one can build his
own DCS with multible PLCs.

# But actually with great engineering to build the DCS from
multible PLCs it will not be the same as pre-built/ready to
use DCS system in its functionality and its features.

# DCS is pre-fabricated system with compatible, integrated,
and tested H/W & S/W - has the following features:

- data collection & management.
- event and history management.
- instrument management.
- alarms management.
- smart and self diagnostics.
- advanced control strategy and easy to build, configure
control loops.
- redundancy.


Regards,

Ahmed Sabry
Control and Instrumentation Engineer
GPC - General Petroleum Company
ahmedsabry.online@gmail.com
CELL.: 00 2 0121367310

Answer / abi

PLC is programmable logic control, while DCS is distribution
control system.
PLC is for operating certain number of devices on the basic
of analog / digital outputs. Normally the output of
industrial devices is in analog, which comes to PLC kits
where they are converted to digital with ADC than executed
instructions according to program specified by user. In
this way we can control multiple devices.
Graphics page available in DCS ( for process diagram) ,it's
easy for process but this facility is not available in PLC

Answer / h.r.mohanty

PLC is used for less Input & Output systems.Where no. of
I/Os are more DCS is prefered.Secondly Scan time of DCS is
much more less than PLC.

Answer / jaibhavani sivaji

now a days both the DCS and PLCs have similar
functionalities, the main difference is in the case of HMI
systems, here in DCS a third party HMI system can be
configured according to the requirement of the end user,
wereas that is not possible in the case of an PLC.
otherwise all the functionalities are same .

Answer / elayaraja

the DCS and PLCs have similar but any problem dcs does not
effect the entaire plant and process.

Answer / bhavin

THE MAIN DIFFERENCE BETWEEN PLC AND DCS IS ITS LANGUAGE.
DCS CAN UNDERSTANDS BOTH HIGHER LANGUAGE AND LOWER LEVEL
LANGUAGE.

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