Question:
What is a disturbance in process control?
Options:
A) Manual override
B) Voltage load variation
C) Desired Setpoint shift
D) Unwanted change
View Answer
Correct Answer: D) Unwanted change
Detailed Explanation
A disturbance is any unwanted or external change that affects the process variable (PV) without changing the setpoint.
It causes deviation from the desired operating condition.
Examples:
- Sudden load variation
- Supply pressure fluctuation
- Ambient temperature change
- Raw material property variation
The controller’s job is to detect the resulting error and correct it.
Key Understanding
Disturbance → Affects PV
Setpoint change → Affects SP
Manual override → Operator action
Disturbances are typically unpredictable and must be corrected by feedback control.
Why Other Options Are Incorrect
A) Manual override → That is operator intervention.
B) Voltage load variation → May be a specific disturbance, but not the general definition.
C) Desired Setpoint shift → That is a command change, not a disturbance.