The invention provides a sensor cartridge comprising: (a) a protective ho using(10), the protective housing being resistant to downhole oilfield envir onment; (b) a sensor (1) within the protective housing able to measure a par ameter of the downhole oilfield environment; (c) an attaching means (5) to i nterconnect with another sensor cartridge (102) and/or a hub(1OO); (d) a dat a communication unit (6) within the protective housing, the data communicati on unit providing wireless communication of the measured parameter to the ot her sensor cartridge and/or the hub when interconnected with the other senso r cartridge and/or the hub; and (e) a power unit (7) within the protective h ousing, the power unit providing power supply to sensor and/or data communic ation unit..
