A robotic work tool system (200) comprising a robotic work tool (100) comprising a lift/collision detection sensor (190), said lift/collision detection sensor (190) comprising a polarity element (191) and at least a first sensing element (192′) and a second sensing element (192″), wherein the polarity element (191) has a first and a second polarity and wherein the first and second sensing elements are configured to each sense a polarity of the first polarity element (191). The robotic work tool (100) is configured to detect a polarity change in the first sensing element (192′) and in the second sensing element (192″) and in response thereto determine that a lift has been detected, or detect a polarity change in the first sensing element (192′) but not in the second sensing element (192″) and in response thereto determine that a collision has been detected.
