Within the metrology community it is generally agreed that uncertainties in measurements shall be calculated and stated in accordance with the guidelines given in ref. (1). The calibration of a set of mass standards in terms of one or more reference standards is a multivariate problem, where the unknown masses are estimated from the known masses and a number of correlated observations of mass differences. A recent paper (2), produced within the framework of EUROMET project 231, describes how to apply the guidelines of ref. (1) in this multivariate case. In parallel to this work, DFM implemented basically the same principles before seeking accreditation for mass calibration in 1992 (3). Extensive software for the control of the weighing process and the subsequent data analysis has been developed at DFM.
The purpose of the project is to exchange experience on how to impletent the principles in ref. (1) in the individual national mass laboratories. If considered appropriate, software could be exchanged between the participants in order to avoid unnecessary duplication of work.
 "Guide to the expression of uncertainty in measurement", published by ISO (1993).
 W. Bich et al.: "Uncertainty modelling in mass comparison", to be published in Metrologia.
 L. Nielsen: "Calibration Methods - Mass", DFM quality system document Q2KAL502.
Within the scope of this proposed project, DFM can offer specific consultancy to individual laboratories, if requested.