A sensor for sensing physiological signal from outside the human body, said sensor comprising an electrode (2) for abutment against the skin and a transmission conductor (3) electrically connected to said electrode (2), said transmission conductor (3) formed from a flexible material, wherein in use a substrate (7) is disposed between the skin and said transmission conductor (3), and said substrate (7) is permeable to moisture and air thereby exposing said transmission conductor (3) to said moisture.
