DCS Distributed Control System Interview Questions 2

DCS Distributed Control System Interview Questions 2 contains Elements Of Distributed Control System, Open Loop Control System, Closed Loop Control System, PLC, Ground Loop, Globe Type Control Valve, Flow, Control Loop.

14. What Are The Basic Elements Of Distributed Control System?
15. Explain Open Loop Control System?
16. What Are The Advantages And Disadvantages Of Open Loop Control System?
17. Explain Closed Loop Control System?
18. What Are The Advantages And Disadvantages Of Closed Loop Control System?
19.
20.
21.
22.

14. What Are The Basic Elements Of Distributed Control System?

Basic Elements of Distributed Control System :

Distributed Control System continuously interacts with the processes in process control applications ones it gets instruction from the operator.

It also facilitates to variable set points and opening and closing of valves for manual control by the operator. Its human machine interface (HMI), face plates and trend display gives the effective monitoring of industrial processes.

15. Explain Open Loop Control System ?

Control System in which output quantity has no effect on the input quantity is called Open Loop Control System.

Open Loop Control System has no facility to correct automatically the error generated in the output. From output of the system no feedback is given back to the input for correction.

In Open loop control system the output can be varied by varying the input. But due the external disturbance system output may change.

Any variation in the output from the desired once again attained by varying the inputs manually.

16. What Are The Advantages And Disadvantages Of Open Loop Control System ?

Advantages

Open loop system is simple and economical.
Construction of open loop system is easier.
Open loop systems are generally stable.

Disadvantages

Open loop systems are inaccurate and unreliable
The changes in the outputs due to external disturbance are not corrected automatically

17. Explain Closed Loop Control System ?

Control system in which the output has an effect on the input quantity in such a manner that the input quantity will adjust itself based on the output generated is called Closed loop Control System.

Open loop control system can be modified in to closed loop control system by providing a feedback.

This feedback automatically corrects the changes in the output due to external disturbance. Hence closed loop control system is called automatic control system.

18. What Are The Advantages And Disadvantages Of Closed Loop Control System?

Advantages:

Closed loop control systems are more accurate even in the presence of non-linearity
The sensitivity of the system may be made small to make the system more stable
The closed loop systems are less affected by noise.

Disadvantages:

Closed loop control systems are costlier and complex
The feedback in the closed loop system may lead to oscillatory response
The feedback reduces the overall gain of the system
Stability is the major problem in the closed loop system and more care is needed to design a stable closed loop system.