Final report on inter-RMO Key Comparison EUROMET.L-K5.2004: Calibration of a step gauge (original) (raw)

The technical protocol for this new KC was drawn up by the Centro Español de Metrología (CEM), based on the previous one drawn in 1999 by the Physikalisch-Technische Bundesanstalt (PTB), Germany, for the first CCL-K5 Key Comparison, but having in mind that this is a new type of interregional comparison, with participants from different regions and a more complicated process linked to the transport of the artefact and customs formalities. Technical Procedure follows also the guidelines established by the BIPM 2. 2.1 Form of comparison The comparison was established in a mixed form, both 'circular' and 'star-shaped'. The artefacts were circulated within a region then returned to the pilot laboratory before circulation in the next region. Because of time constraints, it was not possible to arrange for a 'star-shaped' circulation within each region. CEM acted as the pilot laboratory and NMIA as co-pilot. Although laboratories should communicate all results directly to the pilot laboratory as soon as possible and, in any case, within 6 weeks of completion of the measurements, there were particular bigger delays in communicating such data. The calibration suitability of the artefact was assessed by measurements prior to the start of the circulation of the artefact. Each laboratory received the artefact in turn, according to the pre-agreed timetable, having one month for calibration and transportation. Such pre-agreed timetable was slightly modified along the comparison as result of several laboratories asking for re-measuring the step or because changing the measuring order. Intermediate measurements of the step and a final set of measurements at the end of the comparison were made by the pilot laboratory. 1 Since 1 July 2007, EURAMET e.V., a registered association of public utility under German law, is the successor of EUROMET. EURAMET e.V. is the European Association of National Metrology Institutes and the Regional Metrology Organisation (RMO) of Europe. 2 T.J. Quinn, Guidelines for key comparisons carried out by Consultative Committees, BIPM, Paris Final Report-October 2011 KC EUROMET.L-K5.2004: Calibration of a Step Gauge 6/106 If for some reasons, the measurement facility was not ready or customs clearance took too much time in a country, the laboratory had to contact the pilot and co-pilot laboratories immediately and-according to the arrangement made-eventually to send the standard directly to the next participant before finishing the measurements or even without doing any measurements. If possible the laboratory will be sent the artefact at the end of the comparison. 2.2 Participants The list of participants was taken from the proposed EUROMET Project Form, after circulating it among EUROMET members, and from written contacts maintained with other regions through WGDM members. The participating laboratories should be able to calibrate step-gauges with their best uncertainty less than 1 µm. All participants must be able to demonstrate independent traceability to the realization of the metre. There was an additional requirement to measure the artefacts at a temperature sufficiently close to 20 °C that the uncertainty in the measured expansion coefficient would not dominate the overall measurement uncertainty. By their declared intention to participate in this key comparison, the laboratories accepted the general instructions and the technical protocol and committed themselves to follow the procedures strictly. Once the protocol and list of participants was agreed, no change to the protocol or list of participants could be made without prior agreement of all participants.