Realization of the Highest Level of Traceability in Croatian National Laboratory for Length

Sa？etak Traceability of length measurement to the SI unit meter is realized by means of interferometry, and primary interferometers are used at the highest accuracy levels to perform calibration of national gauge block standards. These devices are expensive, given the fact that they are manufactured on order and used almost exclusively by national measurement institutes. Therefore, The Croatian Metrology Institute/Faculty of Mechanical Engineering and Naval Architecture – Laboratory for Precise Measurements of Length (HMI/FSB-LPMD) decided to retrofit and modify its Zeiss gauge block interferometer. Measurements presented in this paper demonstrate substantial improvements in accuracy and ease of use. These improvements established the highest level of traceability in the Laboratory and enabled it to publish appropriate calibration and measurement capabilities (CMC) value in the BIPM (Bureau International des Poids et Mesures) key comparison database (KCDB) under the Mutual Recognition Arrangement (MRA)