Guidelines for the evaluation of uncertainty budgets for JAVS and QHE based calibrations

Project Description

According to the technical supplement to the MRA, the calibration measurement capabilities (CMC) listed in appendix C of the arrangement are those that are ordinarily available to the customer of an institute through its calibration services. The first CMC review carried out within EUROMET in the EM field showed that the term “service ordinarily available” was interpreted in many different ways.
One of the consequences was that the CMC analysis group had to review services with very low uncertain-ties which are hardly obtainable using conventional transfer standards brought to a NMI for calibration. In the DC field, the critical services were calibrations based on JAVS and QHE standards in relation with cryogenic current comparators.
The aim of this project is to set-up guidelines on the evaluation of uncertainty budgets for the JAVS and QHE based calibrations mentioned above. The guidelines should especially

• discuss and quantify the uncertainty components due to a state of the art device under test
• consider 1/f type noise components of electronic standards (as e.g. Zener references)
   

The resulting guidance documents are intended to improve the comparability of the CMC uncertainty statements.

The work will be organised in the following phases:

• collection and review of the existing information by the participants (literature, existing  guidelines...)
• presentation and discussion of the different opinions during a workshop elaboration of the guidelines

Final Report 2004-01-14

The aim of this project was to discuss the evaluation of uncertainty budgets for the JAVS and QHE basedcalibrations, and to agree among experts on the state of the art uncertainty values in these key fields. Thefocal points of the discussions were:

•  the quantification of the uncertainty components due to a state of the art device under test,
•  the treatment of 1/f type noise components of electronic standards (as e.g. Zener references).

The outcome of the discussions should help to improve the comparability of the CMC uncertainty statements.The topic was introduced during the EUROMET QHE/JAVS experts meeting held during CPEM 2002 in Ottawa. An introduction to the subject of noise in electrical measurements was given by T. J. Witt (BIPM) in his talk “ Serial Correlations in Electrical Measurements”.
In 2003, a workshop on the subject of uncertainty evaluation for calibration against quantum standards was organized during the DC and quantum metrology meeting held in Bratislava on June 16 to 18.
Copies of the presentations given during the workshop can be obtained from the coordinator on request.
It was decided to continue the discussion of uncertainty budgets during the forthcoming experts meetings.