Analysis and Improvement of Measuring Method of Magnetic Fields in Single Sheet Testers

Leakage flux tends to disturb the magnetic field near the H coil in single sheet testers during measurements of high-permeability materials. The authors propose an improved sheet measurement method using two H coils, situated at different distances from the high-permeability material. The field strength in the two coils are measured, and extrapolation to a distance L = 0 is used to obtain the true strength. For high-permeability materials, the measurement accuracy is thus improved greatly over that of the conventional H coil method.