Since the achieved magnetic flux density in steel depends on the excitation history of the steel, precision magnets often suffer from local changes in permeability in the steel of the pole pieces. These effects can be reduced by once fully saturating the pole pieces of the magnet. For high field magnets this can easily be done, but also in low field magnets such a saturation can be achieved by temporarily introducing a bar of steel into the magnet air gap.
展开▼