Design of a Helmholtz coil for low frequency magnetic field susceptibility testing

This paper describes the design of a Helmholtz coil that is a candidate test apparatus for low frequency magnetic field susceptibility testing on military equipment and subsystems. Use of this coil would reduce electromagnetic compatibility (EMC) qualification test time, and subject the equipment under test (EUT) to a relatively uniform field which is representative of the actual electromagnetic environment on some naval platforms. Specifically, this paper presents practical analytical expressions that may be used to design a Helmholtz coil for this unique application. Experimental test results for a three foot diameter coil are presented, including: maximum magnetic flux density vs. frequency, impedance vs. frequency, resonant frequency behavior and the effect of coil separation distances greater than one radius