Modeling of extremely low frequency magnetic field sources using multipole techniques

It is necessary to identify sources of magnetic fields in older to analyze shielding schemes. In general, it is difficult to specify actual sources. Here an alternative method to process magnetic field measurement data to create a simple model of a complex set of quasi-magnetostatic sources is described. This method uses the maximum likelihood estimation technique to calculate the coefficients of spherical and finite length cylindrical multipole sources whose positions have been defined by the user. If a good fit to measured data is achieved, the simple model can then be used to provide input data required by a shielding analysis program.