The characterization of the subsystem is defined by a wide range of physical and mechanical properties and the external conditions. The analytical equations which present the efficiency of EMAT have been obtained for the first time. The equations governing the elastic displacements, secondary field and induced electromotive force take into account a wide range of media properties (electro conductivity varies from pure metals to ferrites; permeability varies from good magnetics to bad ones).

The generalized parameter L has been presented as the ratio of the shear wave length to that of the electromagnetic one. The parameter shows that the influence of the electro conductivity and permeability on efficiency of EMAT differs. At the same time, these characteristics have a similar effect on electromagnetic wave length and therefore on the parameter L. In particular, the maximum of efficiency takes place at log L> 1 for the shear wave and at log L< 1 for the longitudinal one. It has been shown that the geometric parameters of an exciter have sufficient influence on the efficiency of non-uniform EMAT.