The invention relates to an assembly comprising an encoder (1) secured in rotation to the member, said encoder comprising a primary magnetic track (2) and a secondary magnetic track (3) and a sensor (4) having two patterns (5) of sensitive elements which are suitable for detecting the signals supplied by the tracks (2, 3) of the encoder (1), each pattern (5) being arranged at reading distance from a track (2, 3) to form a representative signal of the position of said track, the sensitive elements of a first pattern (5) are based on a magnetoresistive material wherein the resistance varies according to the magnetic signal of the track (2, 3) to be detected, said first pattern being arranged at reading distance from a second track (3) having 2N−1 magnetic pole pairs, the sensitive elements of the second pattern (5) being based on an anisotropic magnetoresistive material, said second pattern being arranged at reading distance from a primary track (2) having N magnetic pole pairs.