For a type of permanent magnet multiloop excitation devices

the magnetic field distribution of the inner and 2 mm above the surface of the ferromagnetic bar was numerically calculated and analyzed by FES while two important sizes is varying

the magnetization effect of the excitation device was analyzed

and the structure of the excitation device was designed.In the experiments

high sensitive giant magnetic resistive（GMR）sensor was employed to detect while the magnetization effect of the excitation device the two parameters is changing.The experimental results are qualitatively in agreement with the simulation.The research results can help to further optimize the design of the excitation device.