Resistance standards with values in the TΩ range play an important role in electrical instrumentation. The calibration of such standards is, thus, a service offered by many metrology institutes. The techniques used to measure very high resistance values differ quite substantially from the calibration techniques applied in the lower resistance ranges. For this reason, the EURAMET technical committee for electricity and magnetism decided in 2008 to organise for the first time a supplementary comparison of resistance at 1 TΩ and 100 TΩ based on well characterized travelling standards.Eighteen European National Metrology Institutes participated in the comparison. With some exceptions, the results supplied by the participants agree reasonably well with the comparison reference value within the expanded uncertainty.As observed in other resistance comparisons, the characteristics of the standards used as transport artefacts ultimately limit the accuracy of comparisons in this field. The transport behaviour is difficult to model and introduces an undesired bias in the laboratory results. The transport uncertainties are at the level of the uncertainties claimed by some of the participants and, thus, limit the meaningfulness of the comparison results.Another remarkable observation is the big difference in the uncertainty statements made by the participants, even in cases where similar measurement systems were used. The results of the comparison allow the participants to critically review their measurement procedures and uncertainty models.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).

Abstract. The "Automated impedance metrology extending the quantum toolbox for electricity" project (AIM QuTE) will extend Josephson impedance bridges capabilities to the whole complex plane with the best level of uncertainties (0.05 ppm). In parallel, fully digital bridges will be developed to reduce the operator workload imposed on national metrology institutes for the realisation of the impedances scales and for calibrations. The target level of uncertainty for these fully digital bridges is parts in 10 -7. Furthermore, sub-pF standards will be developed to establish traceability of very small capacitances. An electronic impedance simulator, which will cover a very large region of the complex impedance plane, will also be realised, it will significantly reduce the number of standards required to link traceability of top level calibration laboratories to national metrology institutes.

It is well known that insulation leakage at high temperatures can be one of the major contributions to uncertainties in measured temperatures above 600 • C. On the one hand, this insulation leakage shunts the sensor resistor leading to systematic errors in the measured temperatures, which are, in principle, characteristics of each thermometer. On the other hand, at high temperatures, degradation of the insulation materials used in the furnaces enhances the decrease of the insulation impedance between the thermometer and the furnace which also causes a systematic temperature measurement error. Two high-temperature standard platinum resistance thermometers have been used to measure these effects in different heat-pipe and three-zone furnaces. One of them was open-circuited by cutting the sensing element end allowing the measurement of the resistance between the two pairs of current-potential leads. Two different setups were used to measure the AC and DC insulation resistances leadto-lead and thermometer-to-furnace. The first one was a teraohmeter with a high value standard resistor in parallel with the leakage resistance to be measured and the other one an LCR meter to perform the AC measurements at different frequencies. In this article, results for both methods are presented.

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This paper presents a brief overview of the current state-of-the-art of Josephson junctions for Quantum-based Voltage Standards fabricated with High-Temperature Superconductors (HTS). A short introduction on the history and technical evolution of Low Temperature Superconductors (LTS) technology is provided for non-specialists. Then HTS technology is summarized and discussed in the context of quantum voltage standard applications. Finally, the two most promising technologies: bicrystal and Focused Helium-Ion Beam junctions are discussed with more detail, analyzing strength, limitations and perspectives in both cases.