Electrolytic conductivity at pure water level

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Main textElectrolytic conductivity in aqueous solutions is a common electrochemical measurement technique in industry. Since it is sensitive to the amount content of dissolved ions in a solution, a limiting value for conductivity is a clear and simple quality criterium for the ionic purity of pure water, roughly ranging from 0.055 μS/cm to 150 μS/cm at 25 °C. International regulations are becoming stricter with regards to metrological traceability to guarantee compliance of measurement results with relevant standards. Consequently, the NMIs active in this area have been facing an increasing request for the calibration of respective conductivity sensors and for adequate CRMs over the past years. A first, regional comparison has been conducted in 2013/14 (EURAMET 1271). Since an increasing number of NMIs, also from other regions, seek providing respective services and establishing CMCs, EURAMET, i.e. the Sub-Committee on Electro Analysis of TC-MC, opened a follow-up comparison to other regions in terms of a supplementary CCQM comparison (EURAMET.QM-S12). The comparison has been conducted in terms of a Round Robin scheme. A conductivity sensor has been sent around between ten participants for calibration at four conductivity levels (0.055, 0.5, 5 and 50 μS/cm at 25 °C). Basically, the measured measurement errors of the device have been compared in terms of conductivity. Additionally, the cell constants calculated from the calibration results have been compared. Apart from very few outliers, the comparison has demonstrated good equivalence of the calibration capabilities.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 the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).