Question:
In a PID controller, what happens if derivative time is set to zero?
Options:
A) D term enabled
B) D term disabled
C) D term is maximum
D) D term = 50%
View Answer
Correct Answer: B) D term disabled
Detailed Explanation
Derivative action is calculated as:
If derivative time (Td) = 0, then:
This means the derivative contribution is completely removed from the PID equation.
The controller effectively becomes:
- PI controller (if integral is active)
- P-only controller (if integral is also zero)
Practical Impact
With derivative disabled:
- No damping improvement
- Higher possibility of overshoot
- Reduced sensitivity to noise
Many industrial loops operate as PI controllers for this reason.
Why Other Options Are Incorrect
A) D term enabled → Incorrect; Td = 0 removes it.
C) D term is maximum → Opposite effect; it becomes zero.
D) D term = 50% → No such fixed behavior exists.