A process for determining the total pitch deviation of a position sensor fitted with a magnetic disk and a magnetic detector, the magnetic disk comprising pairs of magnetic poles, the process includes recording, over one mechanical turn, an angular signal of the magnetic intensity measured by the magnetic detector as a function of the angle of rotation of the magnetic disk, determining zero-crossing positions based on the angular signal recorded and the number of zero-crossing position determined, determining the pole pair lengths based on the zero-crossing positions, and determining the total pitch deviation based on the pole pair lengths.