Question:
If error is zero, what is proportional output?
Options:
A) Max change
B) Zero change
C) Random
D) Negative
View Answer
Correct Answer: B) Zero change
Detailed Explanation
The proportional term is calculated as:
If the error ( e(t) = 0 ), then:
So, the proportional contribution becomes zero change.
Important Clarification
Even if proportional output is zero:
- Total controller output may not be zero
- The integral term may still hold a value
- That value maintains steady-state equilibrium
This is why integral action is required to eliminate offset.
Why Other Options Are Incorrect
A) Max → Proportional output depends on error magnitude.
C) Random → Proportional output is deterministic.
D) Negative → Only if error is negative, not zero.