Control Loop Design and Hardware
Matching Measured and Manipulated Variables
Conceptual Process Control
CCS (Centralized Control System) has disadvantage that the CPU fails, the entire plant gets affected. Also, it is very difficult to apply redundancy due to the large scale.
Distributed Control System (DCS) is a type of specially designed control system used to control complex, large and geographically distributed applications in industrial processes. In this controllers are distributed throughout the entire plant area. These distributed controllers are connected to both field services and operating PCs through high speed communication networks.Components of DCS:
- Field Devices: Control local operations such as opening and closing valves, collecting data from snsor systems monitoring local conditions for alarms. e.g transmitters, electrical drives.
- Input/Output modules: Measure and capture signals from a wide variety of sensors like proximity switches, limits switches and push button switches.
- Controllers: These are comparative devices that receive input signal from a measured process variable, compares this vallue with a set point and determines the appropriate amount of output signal to provide corrective action within a control loop.
- Human Machine Interface (HMI): To present a user interface which makes it easy and self-explanatory, efficient and user-friendly way to operate a machine.
Solved Example: 9137-02
Figure-out the INCORRECT type of mode used in distributed control system from the options given below: (UPPCL JE Elec Sep 2021- Shift I)
A. Computer mode.
Correct Answer: B