The authors review distortions of body surface fluctuations provoked by the action of primary transformers (PT). It is suggested that conditions of PT contact with the body surface may be standardized. As far as transformers measuring the kinematic parameter of fluctuations are concerned, those existing in the absence of any action on the surface should be regarded as undistorted. As for PTs that transform the power parameter, the conditions for undistorted reception involve complete inhibition of the surface under study. It is proposed that the degree of distortions may be estimated in the form of the "measurement method error". It is shown that error of the method can be restricted at the present level, if the design parameters of PT that determine the conditions of contact are chosen in terms of the correlations provided in the paper.