Question:
What is bumpless transfer in PID control?
Options:
A) Sudden output jump
B) Instant PV change
C) Noise filtering
D) Smooth mode change
View Answer
Correct Answer: D) Smooth mode change
Detailed Explanation
Bumpless transfer refers to a smooth transition between manual mode and automatic mode (or vice versa) without causing a sudden change in controller output.
Without bumpless transfer:
- Switching to auto may create a large error
- Controller output may jump suddenly
- Process upset or instability may occur
With bumpless transfer:
- Internal controller states (especially integral term) are aligned
- Output continues smoothly
- No sudden “bump” in actuator position
Why It Is Important
Used during:
- Startup
- Maintenance
- Commissioning
- Operator intervention
It ensures stable operation when changing modes.
Why Other Options Are Incorrect
A) Sudden output jump → That is what bumpless transfer prevents.
B) Instant PV change → PV depends on process dynamics.
C) Noise filtering → That is related to derivative filtering, not mode switching.