Understanding Accuracy & Precision.
Sensors are characterized by 2 different yet important attributes: precision and accuracy.
Precision refers to how close values are to each other. For the same test you will get very similar results.
Accuracy means how close you are of a measured value to a standard value like NIST.
Sensor precision often remains high. Drifting will affect the sensor's accuracy and causing it to be off target.
Fact: Sensors Drift.
Drift is a natural phenomenon for sensors. It affects all sensors regardless of the vendor. It is caused by physical changes in the sensor.
Sensors breathe air. In order to work they need to be in contact with the air surrounding them.
This means that sensors are exposed to conditions that will affect their accuracy.
Main impact comes from contamination from airborne pollutants such a dust, chemicals, vapor and other contaminants. Installation may also impact drift.
The only way to know if your sensor has drifted is through calibration.
The Danger of Drift.
Drifting starts as soon as the sensor leaves the factory or calibration lab.
When sensors do drift, then this is often a slow process. Even too slow to be detected by monitoring systems.
Out Of Tolerance drifting can occur even before your next calibration.
This might compromise your operations and products as the sensor data used has become unreliable.
Companies should implement sensor redundancy configuration with different calibration due dates. This helps reducing the operational risk resulting from drifting.
Especially where temperature & humidity is critical, we do recommend to have a redundant setup with at least an annual calibration cycle and 6 months difference between the respective sensors' calibration due dates.