Resonant eddy current analysis: A selective screening method for electromagnetic shielding materials

The authors discuss both the principle and practice of resonant eddy current analysis (RECA) and its applicability as a screening agent for prospective electromagnetic shielding materials. The RECA methodology relies on the principle that a resonant RLC electrical circuit is detuned by inserting a sample into the coiled inductor. The change in capacitance needed to maintain the original resonant frequency and the change in impedance at resonance are measured. These measured changes define a constraint on an analytical relationship between the material´s conductivity and permeability. In practice, however, measuring changes in frequency is more feasible than changing resonanting capacitors. The RECA methodology is contactless, timely, and efficient. It is inexpensive, requiring only an inductor, several capacitors, and an impedance meter. This method has been used to screen a variety of materials ranging from metals to composite materials