Accurate and well-calibrated sensors are critical for the operation of the water treatment plants run by PUB, especially in the area of water quality control. Over time, sensors measuring crucial parameters, such as pH and total residual chlorine, could drift in their readings. It is difficult for operators to detect these changes in a timely manner, especially if the drift happens very slowly. Current methods of detection include doing a comparison test with the spare sensor(s), verifying the reading through lab tests, and manually analysing the sensor data. Sensor drifts affect the operators' decision making and even the process control systems.
To mitigate the problem of sensor drift, calibrations are done at a predetermined interval. However, as sensors age or if the water they are analysing has variations in water quality, the sensor drift could occur before they are due for calibration. In addition, an improper calibration that is not noticed by staff may also lead to premature inaccuracies in the sensor.