Components of an Automatic Control System

Question 1

What are three examples of process variables?

Answer 1

• Room temperature
• Motor Speed
• Liquid Level

Question 2

What is the function of a sensor?

Answer 2

Measures the process variable and provides feedback information to the controller

Question 3

What is a set point?

Answer 3

Desired value of the process variable

Question 4

What is the difference between an open loop and a closed-loop system?

Answer 4

Open Loop:
- manual system that requires operator
- not self correcting
- controlling device acts independently of process variable
Closed Loop:
- is self correcting
- automatically modifies the process variable

Question 5

What are the five system elements of a closed-loop control system?

Answer 5

• Process variable
• Set point
• Sensor
• Controller
• Actuator

Question 6

What is the difference between a continuous and a discontinuous control system?

Answer 6

Continuous system = power supplied to modify process variable is varied from low to full power value

Discontinuous system = Power supplied is either fully on or off

Question 7

What is the error signal?

Answer 7

Difference between the set point signal and the feedback signal

Question 8

What is the purpose of an actuator?

Answer 8

Alter the process variable (ex. a solenoid valve)