[en] A method has been developed for the measurement of accelerator beam energies to an accuracy of a few parts in 105. As a check, the energy of a resonance in 27Al(p,γ) at Esub(p) = 0.992 MeV has been determined. In addition, a new determination of a resonance energy in 16O(p,p0) at Esub(p) = 6.50 MeV has been made. (orig.)