A sensor device comprising a passive matrix array of electroactive sensor elements arranged in rows and columns. In one example, each sensor element generates a binary sensor signal such that a total signal at each row and at each column enables any pattern of external inputs to be determined. This provides a first way to determine a pattern of sensor elements which are sensing an input using a passive matrix addressing scheme. In another example, each sensor element generates a sensor signal with a different frequency characteristic. This provides another way to enable any pattern of external inputs to be determined.