[en] In order to gain an insight into generation mechanisms for electron beams (EB) in Plasma Focus (PF) the time-evolution of their energy spectra should be well understood. Information of this evolution may be obtained in studies on hard X-ray (HXR) appearing in EB interactions with solid targets. In its general form, this problem is fairly complicated, requiring a great number of multi-parameter time-measurements of HXR spectra and thorough knowledge of the geometry. In the present paper, a method is used which can provide quantitative estimations of temporal courses of the energy and the current of the main EB fraction. The method is based on comparisons between the signals of a pair of identical detectors recording HXR, one of the detectors being covered with an absorbing filter. (author) 5 refs., 3 figs