Differences between NSA 94-106 and IEEE 299 LF magnetic shielding measurements

For the characterisation of the LF magnetic shielding of conductive materials two setups are available. Although for both methods, loop antennas are used, two different configurations are defined. The one referenced in NSA 94-106 (formerly NSA 65-6) is called the parallel setup. The one referenced in IEEE 299 (formerly MIL STD 285) is called the coplanar setup. When performing measurements under similar conditions, different values for the resulting shielding effectiveness (SE) are obtained. This paper will discuss the background why differences are occurring.