Mass calibration is an important activity for national metrology institutes because of the number of measurements on scientific, industrial and legal activities that have traceability to the national mass standards of each country.

In order to evaluate the stated uncertainty and degree of equivalence between CENAM-Mexico and INTI-Argentina on mass calibration a bilateral comparison was agreed between the two laboratories. An additional objective of this bilateral comparison was to demonstrate capabilities in mass calibration by subdivision methods, which are widely used for calibration of weights of the highest accuracy classes.

In order to reach such objectives, two weights of stainless steel were measured in both laboratories from April to June 2005. For the measurements both laboratories used their own facilities, equipment, mass standards and procedures. The measurements made in each laboratory are traceable to the prototype of CENAM and to the national mass standard of INTI, respectively.

Results reported by both participants are consistent within the reported uncertainties, and the largest normalized error (calculated for 1 kg) is 0.89.

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The final report has been peer-reviewed and approved for publication by SIM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).