How should sensors and actuators be calibrated during commissioning?

• A. Calibrating only at start of project.
• B. Replacing sensors with new models regardless.
• C. Ignoring tolerances.
• D. Verify accuracy against accepted tolerance, document method and frequency, and update BAS with calibrated values.

Answer: (D)

Calibration during commissioning ensures sensors and actuators actually reflect real conditions and drive correct control actions. To do this well, you verify accuracy against an accepted tolerance, document the method and frequency, and update the Building Automation System with the calibrated values.

Verifying accuracy means comparing each sensor’s output to a known reference (a properly calibrated instrument or standard) and adjusting as needed so readings stay within the specified tolerance. Documenting the method and frequency provides traceability—the tools used, the environment, the calibration points, who performed it, and how often recalibration should occur. Updating the BAS with the calibrated values ensures all control loops, alarms, trending, and setpoints use the correct data, preventing actions based on erroneous measurements.

Sensors can drift over time due to aging, temperature, or environmental changes, so calibration isn’t a one-time task. A plan for periodic recalibration keeps performance aligned with design expectations and maintains system reliability and energy efficiency.

The other approaches fall short because they either ignore drift and ongoing accuracy, replace hardware without addressing the underlying calibration data, or skip the necessary documentation and traceability that allow future verification and maintenance.