A method of assembling a position sensing arrangement for sensing the position of a revolute joint of an articulated structure. The position sensing arrangement comprises a magnetic sensor assembly 11, 12 and a disc 3 having a first magnetic ring 6 with j magnetic pole pairs and a second magnetic ring 7 with k magnetic pole pairs. A boundary of the disc is constrained by the articulated structure. The method comprises: determining a number of pole pairs of the first magnetic ring to be an integer p such that the first magnetic ring is separated from the constrained boundary by at least the magnetic sensor assembly； determining a number of pole pairs of the second magnetic ring to be an integer q such that the second magnetic ring is separated from the first magnetic ring by a predetermined distance； and if p and q are co-prime: selecting j to be p and k to be q； and assembling the position sensing arrangement by mounting the disc to the articulated structure such that both the disc and the revolute joint are permitted to rotate about the same axis. A claim to a position sensing arrangement is present wherein j and k are co-prime and │j-k │>；1.
