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THE NATIONAL STANDARD OF MASS

The Mass Laboratory's Activities

The priority activities of the Mass Laboratory, which operates within the framework of the Metrology Institute, are ensuring measuring traceability to the international level for the physical quantity of mass, and value transfer to the mass standards of lower hierarchical level in Slovenia. In order to obtain international recognition as holder of the national standard of mass, the Laboratory places the key stress on inter-laboratory comparisons within the framework of the EUROMET organisation, as well as with other national institutions. The R & D work in the field of the physical quantity of mass allows the Laboratory to meet the national needs and to maintain the adequate proficiency.

 

Ensuring traceability of the national standard of mass to the international level

The Laboratory is ensuring traceability of the national standard of mass (which consists of three 1 kilogram stailess steel standards) to the international prototype of kilogram in Paris through a direct comparison with the Platinum-Iridium working mass standards of BIPM. The traceability is assured with the measurement ucertainty of 0,020 mg or less. The Mass Laboratory also takes part in various EURAMET and other international projects, whereby it makes possible, through research work, a reduction of uncertainty of the national standard.

 

Dissemination of the value of the national standard to the lower hierarchical levels in Slovenia

The dissemination of the value is conducted following the accredited procedures for comparison calibration, to own working standards, which are used in calibration of standards of the Slovenian users. The Mass Laboratory can, through dissemination procedures, provide for traceability of all standards in the Republic of Slovenia. The measuring principle is based on comparison measurement of weights, which is performed on one of the four comparator weighing instruments. On the comparator, the mass of the calibrated standard/weight is compared with the mass of the reference standard/weight. The comaprator weighing instruments operate on the principle of incorporated counter-weights and on the basis of an electromagnetic compensation system. The differences between the forces caused by different masses are measured as the difference in electric current, which is proportional to the weight's force of weight. According to the procedures, the mass and the measurement uncertainty are evaluated for the calibrated standard.

 

Scientific research work in the field of the quantity of mass

Besides maintaining the national mass standard and its traceability and dissemination of the 1 kg mass by making a national mass scale, the Laboratory is also dealing with projects of quality assurance and evaluation of the measurement process, study of magnetic properties of weights and with the automation of measurements in a calibration laboratory. These projects are extremely important for the mass measurement field in Slovenia, since through controlling the dissemination procedure, they will provide also a reduction of measurement uncertainty.

 

Standard equipment

The national standard of mass is represented by three 1 kilogram stainless steel weights. Their traceability is assured with the expanded measurement ucertainty of 0,020 mg. Their shape, density, roughness and magnetic properties are within the limits prescribed for the weights of the E1 accuracy class by the international OIML Recommendation 111.