This is an RMO Key Comparison on the measurement of long gauge blocks and will parallel the CCL Key comparison (CCL-K2). The measurements to be made are only the central length at 20°C, measured both ways round. The technical procedure used for CCL-K2 will also be followed for this comparison, though with some small modifications due to the fact that some EUROMET labs which have expressed a desire to participate can only make measurements by mechanical comparison.
This comparison will therefore start with those laboratories which will perform measurements by interferometry, and then continue to those labs which make measurements by comparison. Participation of NPL, PTB and IMGC ensures a link to the CCL-K2 comparison for the purposes of the MRA.
All EUROMET NMIs which wish to participate, should indicate their wish to the pilot laboratory (NPL) and indicate the type of measurement which they will make (interferometry, comparison, other). Any further details such as known periods when staff or equipment is not available in the period 2001 to 2003 should also be indicated, and any other factors which may help the pilot laboratory in producing a draft timetable.
Final Report 2006-02-22
The comparison has been completed and the results are available in the KCDB.
This is an RMO Key Comparison on the measurement of long gauge blocks and will parallel the CCL Key comparison (CCL-K2). This comparison started with those laboratories which will perform measurements by interferometry, and then continued to those labs which make measurements by comparison. Participation of NPL, PTB and IMGC ensured a link to the CCL-K2 comparison for the purposes of the MRA.
The gauge blocks used were: 1 x 150 mm, 3 x 500 mm, 2 x 900 mm, made of steel.
The comparison started in February 2002. At the end of loop 1 in January 2003, two gauge blocks of the original four were found to have changed and had to be replaced. Two replacement gauge blocks were provided by PTB and characterised by both PTB and NPL. Loop 2 then re-started in May 2004, approximately 1 year later than originally planned. The comparison circulation finished July 2005. Draft A report was issued in October 2006 (after a short delay to allow for one re-measurement). Draft B.1 was issued in November 2005 and Draft B.3 was sent for WGDM approval in February 2006.
One participant withdrew their results as they had not completed their equipment at the time of measurement. One laboratory had problems with most gauge blocks, two other laboratories had a single anomalous result each. Apart from these, the results support the CMC claims of the participants, as currently given in the KCDB.
Loan of gauge blocks from JV, NPL and PTB is acknowledged with gratitude, as are repeat measurements by PTB and IMGC.