In a basic control loop, what is the role of the sensor?

In a basic control loop, what is the role of the sensor?

• A. To move the load
• B. To provide power to the controller
• C. To measure the process variable
• D. To compute the controller output

Answer: (C)

The essential function of a sensor in a basic control loop is to measure the process variable and feed that information back to the controller. It detects the current state of the system—like temperature, pressure, or position—and converts that physical quantity into a signal the controller can read. With this real-time measurement, the controller can compare the actual value to the desired setpoint and decide what adjustment is needed. The actuator then carries out that adjustment to bring the process toward the setpoint. Moving the load is the job of the actuator, not the sensor. Providing power to the controller is a power-supply function, and computing the controller output is what the controller does using the sensor data and setpoint; the sensor itself does not perform that calculation.

The essential function of a sensor in a basic control loop is to measure the process variable and feed that information back to the controller. It detects the current state of the system—like temperature, pressure, or position—and converts that physical quantity into a signal the controller can read. With this real-time measurement, the controller can compare the actual value to the desired setpoint and decide what adjustment is needed. The actuator then carries out that adjustment to bring the process toward the setpoint.

Moving the load is the job of the actuator, not the sensor. Providing power to the controller is a power-supply function, and computing the controller output is what the controller does using the sensor data and setpoint; the sensor itself does not perform that calculation.