Sensors fabricated using integrated circuit technology is only sensitive to a relatively small range of concentration. This can be either in the parts per million (PPM) range or percentage range. A sensor (20) is described which has a first group of electrodes (22) which are sensitive to a different range of substance concentration to a second group of electrodes (24). A sensor (20) fabricated according to the invention can be fabricated on a standard CMOS process and is sensitive to a wide range of substance concentration from a few parts per million to percentage range.
