HART Instruments Calibration is required?

A common misconception is that the accuracy and stability of HART instruments eliminate the need for calibration. Another misconception is that calibration can be accomplished by re-ranging field instruments using only a HART communicator. Still another misconception is that the control system can remotely calibrate smart instruments. These are not true. All instruments drift. Re-ranging with just a communicator is not calibration.

A precision calibrator or standard is required. Regular performance verification with a calibrator traceable to national standards is necessary due to:

  1. Shifts in performance of electronic instruments over time, due to exposure of the electronics and the primary sensing element to temperature, humidity, vibration, and other field environmental factors.

  2. Regulations governing occupational safety, consumer safety, and environmental protection.

  3. Quality programs such as ISO 9000 standards for all instruments that impact product quality.

  4. Commercial requirements such as weights, measures and custody transfer.

A calibration procedure consists of a verification (As Found) test, adjustment to within acceptable tolerance if necessary, and a final verification (As Left) test if an adjustment has been made. Data from the calibration is collected and used to complete a report of calibration, documenting instrument performance over time.