Question:
In PID, what does “setpoint tracking” in manual mode mean?
Options:
A) SP fixed
B) PV fixed
C) Output fixed
D) SP = PV
View Answer
Correct Answer: D) SP = PV
Detailed Explanation
Setpoint tracking in manual mode means the controller automatically adjusts the setpoint (SP) to match the current process variable (PV) while the loop is in manual.
SP = PV
This prevents a sudden error when switching back to automatic mode.
Without setpoint tracking:
- SP may differ from PV
- When switched to auto → Large error occurs
- Output may jump abruptly (bump)
With setpoint tracking:
- Error = 0 at the moment of transfer
- Smooth, bumpless transition to auto
Why It Is Important
Setpoint tracking is used to:
- Prevent output bumps
- Improve operator control
- Ensure smooth auto/manual transfer
Why Other Options Are Incorrect
A) SP fixed → That is normal SP behavior, not tracking.
B) PV fixed → PV depends on process, not controller mode.
C) Output fixed → That describes manual mode, not SP tracking.