At least three NMIs maintain facilities for RF and Microwave dielectric measurements but it has been many decades since there has been a formal comparison of complex permittivity between NMIs. Such a comparison is therefore overdue. It is proposed that measurements be carried out upon at least four dielectric specimens with significantly different permittivity and loss. Details of specimens and frequencies of measurement are to be agreed between participants.
Final Report 2015-03-10
The setting up of this Supplementary Comparison was agreed at the CCEM GT-RF meeting on 10 September 2002, having been approved in principle by the Euromet HF Experts meeting in November 2001. While this was an international comparison set up with the approval of GT-RF, it had to be run by an RMO as, at the time, GT-RF were not sponsoring supplmentary comparisons. NPL was the only laboratory available to pilot this comparison and made it known that preparations for the comparison could not start until late-2003/early 2004 when funds would be forthcoming. Three NMIs were directly involved but NPL also received official requests from the NMIs in Poland and Germany to allow the Technical University of Warsaw and BAM respectively to participate in the comparison. This was subsequently agreed.
The completion of the protocol was delayed by the complexities involved in setting up a schedule of measurements. The dielectric specimens eventually chosen originated from three partners. They could not all be measured by all partners, neither could they all be measured at the same frequency by all partners, facts which had consequences for the protocol: sufficient specimens and adequate procedures were required to allow the comparison to be meaningful. After further delay required to achieve this, the comparison commenced late in 2005.
With some further delays, the specimens were measured at the pilot lab and at SNIIM in Russia and were eventually passed on to NIST in the USA. Progress at NIST was halted when a key member of the NIST team died. By 2013 it was hoped that colleagues in the dielectrics team at NIST might be able to take over the comparison, but this has not proved to be possible and, because of re-allocation of staff at NIST, the dielectrics team at NIST has been dissolved. In the circumstances, because of the loss of one of the key partners in the comparison and the inveterate delays, it has been decided to wind the comparison up.
In spite of this, significant experience was gained in setting up the comparison, which might prove of value if subsquent comparisons of a similar sort are set up. It was the first Euro(a)met RF and Microwave comparison to be carried out on materials. More degrees of freedom have to be handled in such a comparison than in conventional artefact comparisons. They include the range of materials to be used, specimen diameter and thickness, allowable specimen permittivities, losses and frequencies and the range of equipment to be used.
Progress Report 2004-03-31
The setting up of this Supplementary Comparison was agreed at the CCEM GT-RF meeting on 10 September 2002 and also approved in principle by the Euromet HF Experts group meeting in November 2000. If piloted by NPL, it may not be possible to run this comparison before October 2003. An alternative arrangement may be for SNIIM to pilot this comparison through COOMET, which may also allow the comparsion to go ahead sooner. Other participants will be welcome.