What is Distributed Control System (DCS)?


#1

A DCS typically uses custom designed processors as controllers and uses both proprietary interconnections and standard communications protocol for communication. Input and output modules form component parts of the DCS. The processor receives information from input modules and sends information to output modules. The input modules receive information from input instruments in the process (or field) and the output modules transmit instructions to the output instruments in the field. The inputs and outputs can be either analog signal which are continuously changing or discrete signals which are 2 state either on or off. Computer buses or electrical buses connect the processor and modules through multiplexer or demultiplexers. Buses also connect the distributed controllers with the central controller and finally to the Human–machine interface (HMI) or control consoles. See Process.

The elements of a DCS may connect directly to physical equipment such as switches, pumps and valves and to Human Machine Interface (HMI) via SCADA. The differences between a DCS and SCADA is often subtle, especially with advances in technology allowing the functionality of each to overlap.

LEVEL 0: FIELD LEVEL As the name suggests this level comprises of the basic field instruments like sensors, transmitters etc. which are directly connected to the process.

LEVEL 1: DIRECT PROCESS CONTROL

This level handles various function as:

•Data Acquisition
•Data Check
•Plant Monitoring
•Open & Close loop Control
• Reporting

LEVEL 2: PLANT SUPERVISORY CONTROL

This level handles various function as:

•Plant Performance Monitoring
•Plant Coordination
•Optimal Process Control
•Adaptive Control
• Failure Detections

LEVEL 3: PRODUCTION SCHEDULING AND CONTROL

This level handles various function as:

•Production Dispatching
•Inventory Control
•Production Supervision
•Production Re-Scheduling
• Production Reporting

LEVEL 4: PLANT MANAGEMENT

This level handles various functions as:

•Market & Customer Analysis
•Order & Sales Statistics
•Capacity & Order Balance
•Order Dispatching
•Production Planning
•TermsSupervision
• Financial Surveys