The preliminary results of the regional key comparison COOMETMP-K15 in the pressure range from 0.3 mPa to 0.9 Pa

Within the COOMET region a regional key comparison (COOMET.M.P-K15) was carried out in order to compare national vacuum standards in the pressure range from 0.3 mPa to 0.9 Pa. The participants were D.I. Mendeleyev Institute for Metrology VNIIM (Russia) and TUBITAK Ulusal Metroloji Enstitusu UME (Turkey) as pilot laboratory. The measurements were carried out from May 2017 to November 2018. Two spinning rotor gauges were used as transfer standards. The effective accommodation coefficients of the rotors had to be determined at eight target points between 0.3 mPa and 0.9 Pa. The uncertainty of the generated pressure in the calibration standard was reported as part of the calibration report by each laboratory. All additional uncertainties that were related to the transfer standard were evaluated by the pilot laboratory in order to have a uniform uncertainty analysis for both participants and in order to emphasize the importance of the reported uncertainty of the generated pressure. Preliminary results have been presented in this paper.