A comparator for materials of low magnetic susceptibility

This paper describes an instrument for comparing the magnetic states of weakly magnetic materials, such as phosphor bronze, copper, filled rubber, etc. The force generated between a suspended magnet and the sample under test causes deflexion of a light beam. The instrument, as used at present, is suitable for comparisons in the range μ = 1 ± 0.00001 to μ = 1 ± 0.0002, but it can be adjusted to cover other values of μ. It has been found particularly useful for detecting magnetic contamination in fine gauge copper wire for instrument work.