The invention relates to a signal inducing device (1, 9, 11, 12, 18, 19, 20), comprising a first material (2, 3, 13, 14) and a second material (4, 16). The first material (2, 3, 13, 14) and the second material (4, 16) show a different magnetic behavior. The first material (2, 3, 13, 14) and the second material (4, 16) are arranged in a way that the resulting magnetic behavior of the signal inducing device (1, 9, 11, 12, 18, 19, 20) varies over a magnetic interaction surface (5, 10) of the signal inducing device (1, 9, 11, 12, 18, 19, 20). The signal inducing device (1, 9, 11, 12, 18, 19, 20) is designed in a way that the magnetic interaction surface (5, 10) shows an essentially smooth surface, in particular with respect to the standard moving direction of the magnetic interaction surface (5, 10).