In order to accurately measure the rotating magnetic field strength

the finite element simulation softwarehas been applied to build 3 D electromagnetic field model. Error of two major methods about measuring magneticfields H coils and Rogowski Chattock coil has been studied. A conclusion that measuring results using H coils aremore accurate has been made and explained. Based on that

the relationship of test error with the distance betweenH coil and surface of sheet has been studied

and the results have been used to the experiments. The error of experi-mental measurement has been reduced finally.