Installation of reference source of low currents for calibration of electrometers

At present, the possibility of realization of reference sources of low currents based on single-electron pumps using the effect of single-electron tunneling and contemporary definitions of the units of physical quantities in the International System of Units is of great scientific interest. However, in everyday metrological practice, this effect has not yet attained the stage of extensive application. In laboratories, for everyday calibration works, the researchers usually use either quantity-produced instruments (sources and meters of low currents and electrometers) calibrated with the help of higher-order standards according to the state verification procedures or specially designed high-precision current sources. In the present work, we present an installation of low-current reference source developed at the All-Russian Scientific Research Institute for Physical-Engineering and Radiotechnical Metrology (VNIIFTRI). The operation of this unit in the mode of generation of ultralow currents is based on the principle of formation of linearly increasing voltage on a reference capacitor. A simplified block diagram of the developed installation of low-current reference source is given. The problems of practical in-service calibration of contemporary electrometers are analyzed. The results of participation of the VNIIFTRI in the international low-current comparisons EURAMET.EM-S44 “Comparison of ultra-low DC current sources” carried out in 2018–2020 are generalized and discussed. The results of metrological investigations of the calibration factor and an example of evaluation of the measurement uncertainty budget carried out at the VNIIFTRI within the framework of these international comparisons are also presented. The research aimed at increasing the accuracy of measurements of low and ultralow currents described in the present work is of great practical importance in the field of electrical measurements, in aeroionometry, and in the ionizing radiation metrology.