System of national standards

The national metrology system is of basic primary importance for every country and a condition for the successful development of the economy, new technologies, science and development of society as a whole. The basic tasks in this area are to maintain the measurement traceability of national standards for individual quantities of the International System of Units (SI) at the international level and to transfer measurement traceability to users for measurement needs of individual sectors such as science, environment, health, nutrition, agriculture, transport, telecommunications, industry and services, trade, taxation, judicial authorities and the police. The basic results of this work are mainly the provision of traceable measurements in the Republic of Slovenia and the transfer of knowledge and professional assistance in implementing the most demanding measurements for a wide range of users.

Due to its great importance to countries, the National Metrology System (NMS) is entrusted to a public authority throughout the world. In Slovenia, the office responsible for the NMS is the Metrology Institute, which in the Republic of Slovenia ensures the traceability of measurements for selected units of the international measurement system of SI units. These are mass, quantity of matter/precious metal, volume and other special units of measurement. For some SI units, the office recognises national standards entrusted to other legal entities. The establishment of a distributed system of national standards in the Republic of Slovenia is determined by the Metrology Act.

The Rules on National Measurement Standards determine the starting points for the establishment of a distributed system of holders of national standards, conditions for the recognition of a legal entity concerning these holders, tasks of these holders, the monitoring, meeting of conditions, implementation of activities and fulfilment of their obligations and the manner and scope of their annual co-financing.

Mass

The national metrology laboratory for mass operates within the Metrology Institute. The priority of the laboratory is to ensure measurement traceability at the international level in the field of physical mass quantity. It is the link between the primary realisation of the mass unit, which it transfers to Slovenian users for various purposes of determining mass through the International Bureau of Weights and Measures (BIPM) in Sevres near Paris.

The comparability of mass measurements worldwide is crucial for international exchange. Therefore, Metrology Institute participates in inter-laboratory comparisons within the EURAMET organisation, which ensure that mass measurements in Slovenia are equivalent to measurements in Europe and the world.

The national standard for weight is represented by three-kilogram stainless steel weights. The maximum calibration measurement uncertainty is 0.020 mg. Mastering the dissemination process of 1 kg mass enables calibration of weights of accuracy class E1. At this level, we also have published CMCs in the BIPM database in the range from 1 mg to 10 kg.

The transfer of values takes place in accordance with accredited procedures to the laboratory’s own working standards, which are used in the calibration of standards of Slovenian users. The laboratory has been accredited by Slovenian Accreditation since 1998. The measurement principle is based on comparative weight measurement. The calibration is performed on comparator scales, where the mass of the calibrated standard is compared with the mass of the reference standard.

Volume

For the field of volume, the Institute has its own laboratory in Celje, with the help of which traceability in measuring volume is ensured from the highest standards all the way to the end user. Volume measurement plays a particularly important role in legal metrology, where measurements in the field of trade in goods and services, healthcare and environmental protection are covered.

Calibration of volume criteria is performed by:

• gravimetric method – weighing of a liquid held by a container,
• volumetric method – pouring into or out of containers of known volume,
• flow method – using accurate flow meters.

The gravimetric method covers volumes between 0.01 ml and 500 l, the volumetric method covers volumes between 50 l and 5000 l and the flow method covers volumes of over 500 l.

Similar to mass measurement, the Institute also participates in inter-laboratory comparisons in the field of volume within the EURAMET organisation.

In accordance with the SIST EN ISO/IEC 17025 standard, the laboratory is accredited in the field of mass and volume for the calibration of weights, scales and volume measuring instruments, SA LK-005.

Time and frequency

The Metrology Institute recognised the Slovenian Institute for Quality and Metrology (SIQ) as the holder of the national standard for the field of time and frequency. As the holder of the national standard, the SIQ ensures the traceability of measurements for time and frequency at the international level. The SIQ is an associate member of EURAMET and has time and frequency related CMCs published in the BIPM database.

Electrical quantities

In the field of electrical quantities, the Metrology Institute recognised the Slovenian Institute for Quality and Metrology (SIQ) as the holder of the national standard. As the holder of the national standard, the SIQ ensures the traceability of measurements for electrical quantities at the international level. The SIQ is an associate member of EURAMET and has electrical quantity related CMCs published in the BIPM database.

Ionizing radiation

The Jozef Stefan Institute is recognised by the Metrology Institute as the holder of the national standard for the field of ionising radiation. As the holder of the national standard, the Jozef Stefan Institute ensures the traceability of measurements for ionising radiation at the international level. The Jozef Stefan Institute is an associate member of EURAMET and has ionising radiation quantity related CMCs published in the BIPM database.

Thermodynamic temperature

In the field of thermodynamic temperature, the Faculty of Electrical Engineering of the University of Ljubljana (FEE) is recognised as the holder of the national standard by the Metrology Institute. As the holder of the national standard, the FEE ensures the traceability of measurements for thermodynamic temperature at the international level. The FEE is an associate member of EURAMET and has thermodynamic temperature related CMCs published in the BIPM database.

Humidity

In the field of humidity, the Faculty of Electrical Engineering of the University of Ljubljana (FEE) is recognised as the holder of the national standard by the Metrology Institute. As the holder of the national standard, the FEE ensures the traceability of measurements for humidity at the international level. The FEE is an associate member of EURAMET and has humidity related CMCs published in the BIPM database.

Pressure

The Institute for Metallic Materials and Technology (IMT) is recognised by the Metrology Institute as the holder of the national standard for the field of pressure. As the holder of the national standard, the IMT ensures the traceability of measurements for pressure at the international level. The IMT is an associate member of EURAMET and has pressure related CMCs published in the BIPM database.

Length

In the field of length, the Faculty of Mechanical Engineering of the University of Maribor (FME) is recognised as the holder of the national standard by the Metrology Institute. As the holder of the national standard, the FME ensures the traceability of measurements for pressure at the international level. The FME is an associate member of EURAMET and has length related CMCs published in the BIPM database.

Quantity of matter

For the quantity of matter, precious metals, the laboratory within the Sector for National Standards and Chemical Measurements at the Metrology Institute operates as the holder of the national standard, which ensures the traceability of its measurements at the international level by participating in inter-laboratory comparisons. In compliance with the SIST EN ISO/IEC 17025 standard, the sector is accredited for measuring the mass fraction of gold and silver in alloys made of precious metals (SA LP-024). CMCs for this area are published in the BIPM database. The sector’s laboratory regularly participates in international comparisons organised by the Convention on the Control and Marking of Articles of Precious Metals (Hallmarking Convention), of which the Republic of Slovenia became a full member in 2009. Since 2004, every year it carries out an inter-laboratory comparative study for measuring the mass fraction of precious metals in MIRS - PT alloys for suppliers' laboratories that independently ensure the conformity of their products with regulations and for chemical laboratories of some foreign testing offices.

In addition to the Metrology Institute, five external institutions are involved in ensuring traceability in the Republic of Slovenia.

For the field of the quantities of amount of substance/Organic Compounds, in particular Fatty Acids, Sterols, Biophemols, Tocopherols, Waxes, Triacylglycerols, Stigmastadienes/in Biological Materials and food, the Metrology Institute recognised the Koper Scientific Research Centre as the holder of the national standard. As the holder of the national standard, the Koper Scientific Research Centre ensures the traceability of measurements for the field of quantities of matter at the international level. The centre is an associate member of EURAMET.

The National Institute of Biology (NIB) is recognised by the Metrology Institute as the holder of the national standard for the field of quantities of amount of substance/Bioanalysis of Nucleic Acids/GMOs and Microorganisms. As the holder of the national standard, the NIB ensures the traceability of measurements for the field of quantities of matter at the international level. The NIB is an associate member of EURAMET and has quantities of matter related CMCs published in the BIPM database.

For the field of quantities of amount of substance/Inorganic Non-metals and their Compounds, Manganese, Loss on Ignition, insoluble and main Components/in Mineral Binders and Mortars, the Metrology Institute recognised the Building and Civil Engineering Institute of Slovenia as the holder of the national standard. As the holder of the national standard, the building institute ensures the traceability of measurements for the field of quantities of matter at the international level. It is an associate member of EURAMET.

The Jozef Stefan Institute is recognised by the Metrology Institute as the holder of the national standard for the field of quantities of amount of substance/Chemical trace Elements/in the organic and inorganic materials. As the holder of the national standard, the Jozef Stefan Institute ensures the traceability of measurements for the field of quantities of matter at the international level. It is an associate member of EURAMET and has quantities of matter related CMCs published in the BIPM database.

For the field of quantities of amount of substance/inorganic Metalloids and their amount of substance/orthophosphate, dissolved anions (chloride, nitrate, nitrite, sulphate), pH/ in Wastewater, the Metrology Institute recognised the National Institute of Chemistry as the holder of the national standard. As the holder of the national standard, the chemistry institute ensures the traceability of measurements for the field of quantities of matter at the international level. It is an associate member of EURAMET. It is an associate member of EURAMET and has quantities of matter related CMCs published in the BIPM database.