Setpoint (control system)

This article is about setpoints in control theory. For other uses, see Set point.
Block diagram of a negative feedback system used to maintain a setpoint in the face of a disturbance using error-controlled regulation. Positive error means feedback is too small (controller calls for an increase), and negative error means feedback is too large (controller calls for a decrease).

In cybernetics and control theory, a setpoint (SP;[1] also set point) is the desired or target value for an essential variable, or process value (PV) of a control system,[2] which may differ from the actual measured value of the variable. Departure of such a variable from its setpoint is one basis for error-controlled regulation using negative feedback for automatic control.[3] A setpoint can be any physical quantity or parameter that a control system seeks to regulate, such as temperature, pressure, flow rate, position, speed, or any other measurable attribute.

In the context of PID controller, the setpoint represents the reference or goal for the controlled process variable. It serves as the benchmark against which the actual process variable (PV) is continuously compared. The PID controller calculates an error signal by taking the difference between the setpoint and the current value of the process variable. Mathematically, this error is expressed as:

where is the error at a given time , is the setpoint, is the process variable at time .

The PID controller uses this error signal to determine how to adjust the control output to bring the process variable as close as possible to the setpoint while maintaining stability and minimizing overshoot.

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