The final technical protocol (version 1.6) of the comparison was established in the beginning of 2001. On April 30, 2001, the main loop has started with the measurements performed by NPL.
Up to now, the comparison is progressing well, with some minor modifications made on the time schedule:
Due to staff changes at LCIE, the measurements must be shifted to the next year. Two additional laboratories joined the comparison:
- CSIR, South Africa (contact person: Erik Dressler)
- Agilent “MTA Rohnert Park”, USA (contact persons: Bart Schrijver, Godfrey Kwan)
Status of the project (main loop, start April 2001) :
- NPL United Kingdom completed
- Agilent Queensferry Scotland (UK) completed
- METAS-> Mechanical and electrical verification completed
- IEN Italy completed
- BNM-LNE (LCIE) France shifted to 2002
- METAS -> Mechanical and electrical verification completed
- Agilent MTA USA completed
- METAS-> Mechanical and electrical verification December 2001
The measurements should be completed by the end of 2002 and the Draft A report will be ready for the participants in early 2003.
Final Report 2005-01-12
The comparison has been completed and the results are available on the KCDB.
The project started in 1996 as an informal comparison between METAS and the commercial Agilent laboratory in Winnersh, which led to a proposal for a EURAMET supplementary comparison (project 555 which later had the code EUROMET.EM.RF-S16 assigned) at the EUROMET HF experts meeting at PTB, Braunschweig, in 1998. A trial round was carried out in 1999/2000 followed by the main loop, which started in April 2001 and finished in June 2003. Nine national metrology institutes and three commercial laboratories participated in this first formal S-parameter comparison in the coaxial 2.4 mm line system.
Measurements of the S-parameters were done at 63 frequencies in the range of 50 MHz to 50 GHz for three attenuators, two matched loads and two mismatch standards. The annex data consists of a subset of seven selected frequencies for which the laboratories were asked to quote uncertainties. In addition the participants had to perform at least four connector orientation measurements and to provide the mechanical pin depth results of the connectors.
For the annex data a comparison reference value was determined using multivariate statistical methods and Monte Carlo techniques. The complete annex data and the results of the analysis are shown in the report. Due to the amount of data it was however not possible to present the full data set at all frequencies and connector orientations in the report.
A CD-ROM was distributed among all participants of the comparison and the EUROMET TC Chairperson in December 2003. The CD-ROM contained the Draft A report and the complete comparison data set including visualisation tools and additional information about the comparison. The CD-ROM is only available to the participants since it contains confidential pre-publication data.
During the feedback round of Draft A three participants required to change/remove some of their measurements. The requests were approved by the other participants and required a reanalysis of the whole data set. The updated results and other rather small changes in graphical representation of the data and language, all based on constructive suggestions and comments of the participants, were implemented in Draft A version 2, which was sent out in August 2004.
Draft A version 2 was then accepted as Draft B by the participants and subsequently presented to the RMO TC-EM for approval to become the final report in November 2005. In these last steps no substantial changes to the report were requested anymore.