Today, there is great scientific interest in the possibility of implementing reference sources of low currents based on single-electron pumps using the single-electron tunneling effect and the modern definition of the SI system. However, the practical use of this effect in everyday metrological practice has not yet reached the stage of widespread use. Typically, for routine calibration work in laboratories, either mass-produced instruments (low current sources and meters, electrometers) are used, which are calibrated against higher standards, or specially designed precision current sources. The article describes a reference installation developed on the basis of the VNIIFTRI, where in the mode of generating ultralow currents the principle of forming a linearly increasing voltage on a reference capacitor is used. A simplified block diagram of the reference setup is shown. Issues of practical adjustment of modern electrometers are considered. The generalized results of participation in international comparisons on low currents EURAMET.EM-S44 “Comparison of ultra-low DC current sources” conducted by national metrological institutes in 2018–2020 are presented. The results of a metrological study of the calibration factor Q and an example of calculating the uncertainty budget of measurements carried out at the VNIIFTRI as part of these international comparisons are presented. The research described in the article to increase the accuracy of measurements of small and ultra-low currents of this level has valuable practical significance in the field of electrical measurements, in aeroionometry and metrology of ionizing radiation.