High accuracy magnetic moment measurement system using compensated Helmholtz coils

The uncertainty of instruments currently available for measuring magnetic moment is about 0.5%. To further improve the measurement accuracy of the magnetic moment for permanent magnets, a measurement system using compensated Helmholtz coils and a phase-locked method is developed. The coil constant of the Helmholtz coils is calibrated using null detection method. The uncertainty of the magnetic moment for the new method is 0.09%. The principle and results are discussed.