A national comparison of dc resistance at 10 MΩ and 1GΩ level was organized by the Electromagnetic Division of National Institute of Metrological Research (INRIM, Italy) and piloted by the same Division. This comparison took place between January and April of 2008 with the participation of 8 secondary Laboratories accredited by the Italian Accreditation of Calibration Laboratories Service (SIT). The travelling package included a wire-wound 10 MΩ standard and a thick film-type 1 GΩ standard in a wooden anti-shock container designed by INRIM. The obtained results indicate that the differences at 10 MΩ and 1 GΩ between each laboratory's value and its reference value are all within the expanded relative uncertainties of these differences.
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A temperature-variable high accuracy (TVHAR) 10 kΩ resistor has been developed at the National Institute of Metrological Research, (INRIM), in order to transfer the traceability to high accuracy multifunction instruments used in the accredited calibration laboratories. The TVHAR consists of ten 100 kΩ nominal value resistors inserted in a copper block and connected in a parallel configuration. The thermal stability of the copper block is obtained with a temperature controller. In this paper details of the development of the TVHAR and of its thermal behaviour are reported. From preliminary results its relative short-time stability (2h) is on the order of a few parts in 10-8, a negligible temperature coefficient around 23°C and a power coefficient on the order of -4×10-6/W.
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