Realization and transfer of the candela and the lumen at INM according to CIPM recommendations

Currently, INM maintains the units of the luminous intensity and luminous flux with groups of standard lamps, calibrated by the BIPM laboratory in 2002. Following the decision to stop the calibration of such standards at BIPM, INM decided to proceed to the development of new reference standards, based on the definition of candela and according to the CIPM recommendations. Within the proposed project, BNM-INM-France and INM Romania will co-operate in order to develop and improve the techniques and the standards needed for the candela realization at INM according to the definition. Next, the lumen will be realized using the goniophotometric technique. In order to validate the INM realizations and capabilities, bilateral comparisons with BNM-INM will be organized as follows:a. For the luminous intensity, a first comparison (in process) is aimed at validating the INM capability to realize the unit according to the definition. The unit was realized at INM with a V(l) filtered trap detector that was further compared to the reference standards of BNM-INM (group of lamps being involved in the CCPR-K3.a key comparison).A second comparison is planned for October 2004-March 2005 in order to assess the INM capability in transferring the unit to secondary standards (lamps). Some lamps (2 or 3) will be first calibrated at INM with respect to the newly developed absolute standard (filtered trap detector) then by BNM-INM, against the French laboratory standards. b. For the lumen, given the complexity of the absolute realization, only one comparison is envisaged, at the secondary standards (lamps) level. First, three lamps will be calibrated by INM against the luminous intensity newly developed absolute standard, using the goniophotometric technique then by BNM-INM against the French laboratory reference standards and after that, again at INM, using the same reference standard and technique. This comparison is aimed at validating and improving the INM CMC and to provide useful information on the accuracy and reliability of the lumen derivation at INM. Currently, INM maintains the units of the luminous intensity and luminous flux with group of standard lamps, periodically calibrated by BIPM. Following the decision to stop the calibration of such standards at BIPM, INM decided to proceed to the development of new reference standards, based on the definition of candela and according to the CIPM recommendations. A first attempt was made during 2002 when a filtered trap detector was developed and used to realize the candela at INM. A bilateral comparison with BNM-INM showed that the candela value obtained about 1.1 % lower than the CCPR K3.a reference value. It was decided to improve the techniques and the instrumentation, especially on the correcting filter.Within the proposed project, BNM-INM-France and INM Romania will co-operate in order to develop and improve the techniques and the standards needed for the candela realization at INM.Next, the lumen will be realized. Two methods: goniophotometric and absolute integrating sphere will be considered in order to choose the most appropriate for implementation at INM.Following, bilateral comparisons will be performed in order to validate the new standards, the methods and techniques developed at INM. For the luminous intensity, two bilateral comparisons are envisaged: one involving the new reference standard and a second one making use of lamps, in order to evaluate the INM capability at the unit transfer level.For the luminous flux, only one comparison is envisaged. Lamps calibrated at INM with respect to the new standard and method will be subsequently calibrated by BNM-INM in order to obtain relevant information about the INM capability in realizing and transferring the lumen.

Further Information

Progress report was submitted in May 2004. The project is financed within a Romanian Government research programme.

Subjects
Photometry and Radiometry (PR)
Coordinator
Jean Bastie, LNE-INM (France)
Coordinating Institute
LNE-LCM/CNAM (France)
Participating Partners
INM-RO (Romania)