An Empirical Study of ELF and VLF Shield Cans

An empirical ELF and VLF study of 1/16- and 1/32-inch thick shield cans (stainless steel, aluminum, copper, Polyform, annealed Hipernom, and annealed and unannealed coldrolled steel, mumetal, and Co-Netic) was performed to investigate shielding effectiveness versus frequency characteristics with emphasis on the effects of machining (notches, slots, holes, and louvers), dropping, annealing, and welding. The erratic nature of many of the shielding functions is explained by the resonance theory of shielding, and the shielding characteristics of certain shield cans are compared. The paper also presents a brief introduction duction to the automated testing system used during this study to obtain the numerous shielding effectiveness versus frequency curves that were required.