Question:
What is meant by a reverse-acting controller?
Options:
A) PV↑ → Out↓
B) PV↑ → Out↑
C) SP↑ → Out↓
D) Error = 100
View Answer
Correct Answer: A) PV↑ → Out↓
Detailed Explanation
A reverse-acting controller is defined by the relationship between the process variable (PV) and the controller output.
In reverse action:
- If PV increases,
- The controller output decreases.
The output moves in the opposite direction of the PV.
Example
Steam temperature control:
- Temperature (PV) rises
- Controller output decreases
- Steam valve closes slightly
- Temperature reduces
This opposite movement defines reverse action.
Why Other Options Are Incorrect
B) PV↑ → Out↑ → That describes direct-acting control.
C) SP↑ → Out↓ → Controller action is defined by PV behavior, not SP change.
D) Error = 100 → Not related to controller action type.