What is the purpose of a setpoint in a control loop?

• A. The measured process variable used for feedback
• B. The reference value the controller aims to reach
• C. The maximum output the actuator can produce
• D. The ambient conditions affecting the process

Answer: (B)

In a control loop, the setpoint defines the target value for the system’s output. It’s the reference the controller aims to reach, and the controller gauge how far the actual measurement (the process variable) is from that target. The difference between the setpoint and the measured value is the error the controller acts on to produce the necessary actuator signal to reduce that gap. The setpoint can be fixed or change over time if the desired target changes. It is not the measured variable itself, not the actuator’s limit, and not the ambient conditions—those are disturbances or constraints, not the target value.