A measurement system having a first magnetic field sensor and having a magnet for generating a magnetic field, in which the magnet has a first pole face and a second pole face, wherein an axis of rotation is defined perpendicular to the first pole face and perpendicular to the second pole face, wherein the magnet is supported for rotation about the axis of rotation, in which the first magnetic field sensor is positioned facing the first pole face and at a distance from the axis of rotation, in which the magnet has a rotational asymmetry of the flux density in the region of the first pole face, wherein the flux density of the magnet in the first magnetic field sensor can be adjusted between a maximum and a minimum by rotation of the magnet about the axis of rotation.