The Electron Counting Capacitance Standard currently pursued at PTB aims to close the Quantum Metrological Triangle with a final precision of a few parts in 10 7 . This paper reports the considerable progress recently achieved with a new generation of single-electron tunnelling devices. A five-junction R-pump was operated with a relative charge transfer error of five electrons in 10 7 , and was used to successfully perform single-electron charging of a cryogenic capacitor. The preliminary result for the single-electron charge quantum has an uncertainty of less than two parts in 10 6 and is consistent with the value of the elementary charge.

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For the first time, a EURAMET comparison was performed in the field of small DC currents below 1 nA. The capabilities of thirteen European and non-European National Metrology Institutes for traceable calibrations of picoammeters have been compared. For that purpose, two different commercial picoammeters were used as travelling instruments. They were calibrated at current values of ±100 fA, ±1 pA, ±10 pA and ±100 pA. The accuracy achieved was to a large extent limited by the stability of the travelling instruments. The expanded relative uncertainty (k = 2) of the reference values varied between 2.7 × 10−4 and 1.9 × 10−5, depending on the current ranges and the travelling instruments. There was a good agreement between the results of most of the participants.Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by EURAMET, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

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