Question:
In a PID loop, what is the setpoint (SP)?
Options:
A) Measured value
B) Desired value
C) Output value
D) Error value
View Answer
Correct Answer: B) Desired value
Detailed Explanation
The Setpoint (SP) is the desired or target value that the process variable (PV) should reach and maintain.
Examples:
- Desired temperature = 150°C
- Desired pressure = 5 bar
- Desired flow = 100 m³/hr
The controller continuously compares:
Error = SP - PV
If SP changes, the controller adjusts the output to move PV toward the new target.
Why Other Options Are Incorrect
A) Measured value → That is the Process Variable (PV).
C) Output value → That is the Controller Output (CO).
D) Error value → Error is the difference between SP and PV.
Quick Memory Tip
- SP = Target
- PV = Actual
- CO = Action
- Error = SP − PV