Sensor networks comprising sensors are often used for monitoring variables in certain environments. Each sensor comprises a sensing mechanism, and a transmitter for transmitting sensed data to a base unit. If the sensors are wireless, transmission of the data is performed by a wireless transmitter.
Once sensors have been deployed in an environment, they generally have a limited lifetime. For example if sensors use a battery as their power source, the battery will eventually become discharged. Even before this however, sensors tend to lose calibration. Thus, whereas initially the data sensed by the sensors can be relied upon as being accurate, at some stage calibration is lost to such an extent that the data is no longer useful.
Replacing sensors when their readings are still accurate is wasteful and costly. On the other hand, relying on results from sensors that have lost calibration leads to inaccurate data, which can be misleading or at worst dangerous. Therefore there is a need to know how calibrated sensors are.
A problem is that the rate that the calibration of sensors in a sensor network is lost can vary depending on various factors including environmental conditions and the electronic circuitry in the sensors, and can be very difficult to predict. Thus there is a technical problem in determining the extent of calibration loss in the sensors of a sensor network.