A method for detecting a phase angle difference between a first periodic measurement signal and a second periodic measurement signal, wherein, for the purpose of determining a torque applied to a shaft, the two periodic measurement signals describe a rotation of the shaft at an axial distance from one another including superimposing a periodic auxiliary signal which simulates a previously known rotational speed for the shaft on the first periodic measurement signal in order to form a superimposition signal, and determining the phase angle difference on the basis of the superimposition signal and the second measurement signal.