Abstract: The invention concerns a sensor that, when exposed to a fluid, develops a measurable characteristic that is a function of the level of an analyte in the fluid and of a calibration quantity of the sensor. A calibration quantity is some physical, chemical or other inherent property that the sensor possesses that affects its response to the analyte. The sensor includes an RFID tag that receives, stores and conveys information representing the calibration quantity. The wireless device is incorporated into or attached to the sensor during the manufacturing process and before the sensor is calibrated. The wireless device can be written wirelessly once the calibration has been done. This does not involve any additional handling of the sensor and can be done once the sensor has been placed into a protective enclosure.