Which control process requires feedback to maintain a desired set point?

• A. Automatic control process
• B. Sequential control process
• C. Interlox control process
• D. Status

Answer: (A)

Maintaining a target value in the presence of disturbances is achieved by a feedback-based regulator. In an automatic control process, the sensor continuously measures the actual process variable and compares it to the desired set point inside the controller. If there’s any difference (an error), the controller sends a corrective signal to an actuator to adjust the process until the variable returns to the set point. This ongoing loop is what keeps the system stable and at the desired value even when things change or external disturbances occur. A home thermostat illustrates this well: it reads the room temperature, compares it to the set temperature, and turns heating or cooling on or off to maintain that target.

Sequential control relies on a fixed sequence of steps and doesn’t continuously correct based on current measurements, so it isn’t inherently about holding a set point. Interlocks are safety mechanisms that prevent certain actions rather than regulate a value to stay at a set point. Status simply reports current conditions without actively driving adjustments.