[en] We have measured the cyclotron frequencies of He⁺, H⁺₂ and D⁺₂ ions in a room temperature Penning trap. The resonances were detected destructively by a time-of-flight technique. The statistical uncertainty of the resonance frequencies was generally below 1 ppb. A detailed account of measures to minimize systematic frequency shift is presented. Using the accepted values for the proton and deuteron mass we obtain a value for the ⁴He mass: M(⁴He)=4.0026032489(22) (0.5 ppb). It is in agreement with the accepted value. (orig.)