A sensor device for placement on a rail track and a method for placing the sensor device. The sensor device includes one or more permanent magnets positioned such that the sensor device is mountable on the lateral side of the rail track by magnetic attraction. A housing includes a base side, a mounting side, and a top side opposite the base side, where the mounting side includes first, second and third contact edge regions configured to be in contact with the rail track. The second contact edge region is positioned outwardly from a first plane through both the first contact edge region and the third contact edge region, and the second contact edge region is positioned between a second plane parallel to the top side and through the first contact edge region and a third plane parallel to the second plane and through the third contact edge region.