What is the manipulated variable in a process?

The manipulated variable in a control process is the variable that is actively adjusted to achieve the desired outcome, thereby closing the gap between the set point and the controlled value. This action is typically part of a feedback control system, where the objective is to maintain the controlled variable—such as temperature, flow rate, or pressure—at a specific set point.

In practice, when the control system detects a deviation in the controlled variable from the desired set point, it will manipulate the appropriate variable to correct this deviation. For instance, in a temperature control system, if the temperature drops below the set point, the manipulated variable could be the amount of heat supplied to the system, which is adjusted to bring the temperature back to the desired level.

Understanding this concept is critical for effective control system design and operation because it highlights the role of the manipulated variable as the means through which desired performance is achieved within a process.