What is DCS?


Distributed Control System refers to a control system usually of a manufacturing System, process in which the controller elements are not central in location but are distributed throughout the system with each component sub-system controlled by one or more controllers DCS was introduced in 1975 by:

»Honeywell-TDC 2000
»Yokogawa – Centum
• Today Centum is Having around 14,000 installations around the world.
Advances in centum: CS1000 and CS3000
Advances in Honeywell: TDC-3000, TPS & at present EPKS
It distributes information and control functions that previously required central computer.
A DCS typically uses computer(usually custom designed processor) as a controller and proprietary interconnection
 and protocols for communication.
 It is not concentrated in a specific geographic location or around a single center computer

DCS General Architecture


DCS General Architecture
                                                   DCS General Architecture

DCS Elements

Data Acquisition Unit: Digital (discrete) and analog I/O can be handle.

Batch Sequencing Unit: This unit controls a timing counters, arbitrary function generators, and internal logic.

Local Display:This device provides analog display stations,and video display for readout.

Bulk Memory Unit: This unit is used to store and recall process data.

General Purpose Computer: This unit is programmed by a customer or third party to perform optimization, advance control, expert system, etc
Central Operator DisplayThis unit typically contain several consoles for operator communication with the system,and multiple video color graphics display units
Data Highway: A serial digital data transmission link connecting all other components in the system. It allow for redundant data highway to reduce the risk of data loss
Local area Network (LAN)

Advantages of DCS:

 Access a large amount of current information from the data highway.
 Monitoring trends of past process conditions.
 Readily install new on-line measurements together with local computers.
 Alternate quickly among standard control strategies and readjust controller parameters in software.
 sight full engineer can use the flexibility of the framework to implement his latest controller design ideas on the host computer

What is the difference between a PLC and a DCS?


                                                DCS V/S PLC


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