Case for screening instruments against magnetic stray fields - is made by insertion into each other of hollow rectangular metal units to form multilayer surround

摘要

The rectangular units may be open topped boxes which nest inside each other with their axes at 90 deg. Altogether four hollow units are provided; the innermost unit is made of copper, and the other, outer units of a high permeability soft magnetic alloy, consisting of 76% nickel, 17% iron, 5% copper, 2% chromium and at most 0.1% of carbon; the axis of the copper unit is parallel to the axis of highest magnetic sensitivity of a component mounted in the screening case; axes of the remaining units are in turns parallel to the three spatial axes of a rectangular coordinate system.