What step is essential when performing a loop check to confirm actuator movement?

• A. Test actuator movement in response to a setpoint change.
• B. Verify sensor offset by calibration.
• C. Update the firmware of the DDC controller.
• D. Inspect the building's main power supply.

Answer: (A)

The key step is to command a known change in the setpoint and observe the actuator’s response. This directly tests the loop’s ability to translate a control signal into physical movement, confirming that the actuator, its drive signal, and the feedback path are all functioning correctly. By applying a setpoint change and watching how the actuator moves (direction, range, and timing), you verify that the control loop is capable of driving the process toward the new value. Other tasks like calibrating sensor offsets, updating firmware, or inspecting power can matter for broader reliability, but they don’t prove that the actuator actually moves in response to a control command.