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THE NATIONAL STANDARD OF LENGTH

Activities of the Laboratory for Production Measurement

The Laboratory for Production Measurement has been operating, within the Institute of Production Mechanical Engineering of the Faculty of Mechanical Engineering at the University of Maribor, since 1968. From the very beginning, the Laboratory has been performing research, development as well as educational work and services in the field of production measurements (measurements of the geometry of workpieces in production) and quality assurance.

The Laboratory traditionally cultivates close contacts with the Slovenian companies (especially in the metalworking and other industries), helping them to solve the practical problems in dimensional measurements. The Laboratory conducts research and development projects and provides consulting and training of staff in industry. Besides the maintenance of the national standard, the Laboratory's infrastructure also allows the calibration of standards of length and measuring equipment for the verification of legal measuring instruments.

The Laboratory has so far carried out 70 complex R&D tasks within the framework of national and international R&D programmes. The bibliography of the Laboratory's associates comprises over 300 different publications.

 

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

At the moment, the Laboratory for Production Measurement is ensuring traceability of the national standard of length in the primary laboratory of the Nederlands Meetinstituut, the Netherlands, (for laser interferometer), in the primary laboratory of the Physikalisch-Technische Bundesanstalt (PTB), Germany (for large length standards up to 1000 mm), and in the national laboratory of BNM-LNE, France (for small length standards up to 100 mm). In view of reducing measurement uncertainty, the Laboratory also participates in inter-laboratory comparisons.

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

The dissemination of the value by means of national standards is conducted following the accredited procedures for comparison calibration, to the laboratory's working standards, which are then used for calibration of customers' standards. The comparison measurement is performed by a comparison measuring instrument (comparator). The length of the calibrated standard (gauge block) is compared to the length of the reference standard, which is traceable to the primary standard of length (international level). The comparison measuring instruments (a comparator up to 100 mm, and a comparator up to 1000 mm) operate on the principle of differential measurement of deviations by two inductive pick-offs of 0.01 (m resolution.

Scientific research work in the field of the quantity of length

The Laboratory performs scientific research in its endeavours to improve the measurement uncertainty of travelling standards, and to extend the range of the quantity. Within the framework of tasks related to the national standard of length, the Laboratory is primarily endeavouring to improve the metrological procedures, in view of reducing measurement uncertainty in the same set of gauge blocks. It also confirms its results in inter-laboratory comparisons. The Laboratory is also improving its measurement methods in calibration of large length instruments, thereby covering a wider range of needs of the Slovenian market.

 

Standard equipment

The measurement standard consists of:

     

  • a set of 122 gauge blocks of lengths ranging from 0.5 to 100 mm of the 00 quality class. The gauges are made of steel with linear temperature expansion  α = 11,5 x 10-6 K-1,
  • a set of 8 gauge blocks of lengths ranging form 125 to 500 mm of the K quality class. The gauges are made of steel with linear temperature expansion α = 11,5 x 10-6 K-1,
  • gauge blocks of lengths 600 mm, 700 mm, 800 mm, 900 mm and 1000 mm, of the K quality class. The gauges are made of steel with linear temperature expansion α = 11,5 x 10-6 K-1.

Accessories include a comparator for the transfer of measures up to 100 mm, a comparator for the transfer of measures up to 1000 mm, a glass cylinder for checking the flatness of measurement surfaces on the standards, and a set of special standards (11 pieces), and an additional standard of 500 mm for the calibration of the comparator. The special set of standards and the additional standard of 500 mm have the same quality as the basic set, and their traceability is ensured in the same way.