Abstract: The magnetic induction intensity of Helmholtz coil common axis point is measured by using both the FD-HM-I type Helmholtz coil and high sensitivity of milli Tesla meter. Through changing the positive and reverse direction of current of Helmholtz coil, the effect of magnetic field is eliminated, and then the permeability of vacuum is measured accurately.

Key words: permeability of vacuum, Helmholtz coil, magnetic field intensity