Modern components of activities and models of national metrological institutes

Economies and societies are constantly changing and developing, so national metrological systems also need changes and adaptation to modern conditions. National Metrological Institutes (NMI), as one of the main elements of the national metrological infrastructure, are responsible for the development and maintenance of national standards, conducting scientific research in the field of metrology. There are significant risks due to the lack of an effective metrology infrastructure at the national level. The article analyzes the main modern components of NMI activities and offers options for models of NMI functioning depending on the existing metrological infrastructure, taking into account various risks of the operation of such infrastructure.


Introduction
In the classic and short definition, metrology is the science of measurements and their application [1] .
Metrology includes all theoretical and practical aspects of measurement, regardless of measurement In manufacturing, measurement accuracy is critical to ensuring product and process quality.In many scientific disciplines, high-precision measurements play a key role in confirming hypotheses, making observations, and collecting data.The development of new technologies and materials often requires the introduction of new measurement methods that allow evaluating the characteristics of new materials, devices, and systems.In trade, measurement is the basis for setting prices and exchanging goods.In medicine, measurement accuracy is vital from diagnosis to treatment.Measurements are important for environmental monitoring, pollution detection, and safety.
gal Metrology (OIML) and the International Bureau of Weights and Measures (BIPM), contains advice to national authorities on issues aimed at developing their national metrology systems (NMS).There is an urgent need to harmonize the main elements of the institutional and legislative framework of the NMS.
The document contains a checklist of elements to consider when developing national legislation and a model law that can be used for this purpose.
It is important to use and introduce a single glossary of terms into the national legislation on metrology.The International Vocabulary of Terms in Legal Metrology (VIML) OIML V 1 [4] , as well as the International Vocabulary of Metrology (VIM) OIML V 2 [1] , contains basic concepts that should be applied at the national level to harmonize the main provisions of the NMS operation.
NMIs, as one of the main elements of the national metrological infrastructure, are responsible for the development and maintenance of national standards, conducting scientific research in the field of metrology.To promote the international recognition of these standards and their associated measurement capabilities, NMIs participate in international benchmark reconciliations [2] .In some countries, the NMI functions are not limited to a single organization, so there is a distributed system where several different metrology institutes develop and maintain national standards in their specialized fields and work collectively with an appropriate level of coordination.
There are significant risks due to the lack of an effective metrology infrastructure at the national level.It is important that each country has an adequate metrology infrastructure with the necessary funding.In [5] , five models (models A-E) of multifunctional NMS were proposed, and the main characteristics of their functioning were established.Implementation of the proposed models can be carried out in any country by one or more organizations, depending on their metrological capabilities.
In [6] , some modern components of the evaluation of the NMI activity of Ukraine are considered, however, the main attention is paid in the work to the evaluation criteria of scientific activity generally A measurement infrastructure is a system of organizations, structures, standards, equipment, and procedures that ensures measurements are performed with high accuracy, reliability, and reproducibility.It is fundamental for the development of modern technologies, as it provides the basis for accurate determination of physical quantities used in technological processes and scientific research.The main components of the measurement infrastructure include national metrology institutes (NMIs), national standards, high-precision measurement equipment, quality management systems, international cooperation, metrology programs and projects, and regulatory authorities.
The National Metrology Institute (NMI) is a specialized organization responsible for the development and maintenance of measurement infrastructure or metrology infrastructure in a given country.It plays a key role in ensuring the accuracy, reliability, and reproducibility of measurements in various fields such as industry, science, medicine, environment, etc.
NMIs play an important role in supporting scientific progress, innovation, and technological development, ensuring the reliability and accuracy of measurements, which are the basis of many modern achievements [2,3] .
The main functions of NMI, in general, include

Analysis of latest publications and purpose of the research
The international document OIML D 1 [3] , jointly developed by the International Organization for Le-applied in developed countries, as well as to the activity of NMI within the framework of the multilateral Agreement on the mutual recognition of national standards and calibration and measurement capabilities of the International Committee of Weights and Measures (CIRM) -CIRM MRA.
Considering the complexity of modern metrological activity, there is an urgent need for coordination of various activities in the NMS.This may include special measures to supervise the implementation of the national metrology policy.National standards are a key part of the NMS.The national metrological infrastructure needs means to spread knowledge and competence in metrology [3,5] .
The main goal of this article is to conduct an analysis of the main modern components of NMI activities and establish variants of NMI functioning models depending on the existing metrological infrastructure and taking into account various risks of the operation of such infrastructure.

General approaches to ensuring the effectiveness of the functioning of the NMI
Economies and societies are constantly changing and developing, so the NMS also needs changes and adaptation to modern conditions.Technological changes, in particular, create new challenges for NMS by changing the characteristics of the products to be measured.At the same time, however, they can provide new ways for the NMS to function, opening up new opportunities for more efficient and effective work.Both technological changes and the introduction of new work methods require metrologists of all fields of activity and work levels to develop their skills and competencies.Therefore, both training and continuous professional development are vital for the entire NMS [3] .
In an ideal case, the country can create a single NMI that will cover all its needs in the field of both scientific and legal metrology (LM).However, for a number of reasons, this may not always be practical-ly possible, so the NMI functions may be performed by more than one scientific metrology organization.This is possible in the case when responsibility for different areas of metrology was traditionally distributed between different institutes in the country.
In any case, the impartiality of institutions is strictly required.Therefore, appropriate financial resources should be provided for the long-term stability and sustainable development of NMI.
In many countries, the functions of LM are performed by NMI.In other countries, such activities may be distributed among several metrological institutes, which specialize in different fields and subfields of measurement, under appropriate general coordination of such activities.However, in all cases, it is strongly recommended to develop synergies between activities in the field of scientific and legal metrology, in particular, either by combining scientific and legal metrology in one institute or at least by establishing close cooperation between institutes responsible for these two fields of metrology [3] .
The reasons for the close coordination of metrological works at the national level are new areas and technologies in LM, which technically approach the accuracy to the level of national standards.This requires new methods of calibration, testing, and verification and new standards of measurement, which should be developed within the framework of NMI activities in the field of scientific metrology.Ensuring a high level of competence in metrology is becoming increasingly important in LM, so the exchange of skills and competences between all areas of legislative and scientific metrology is becoming increasingly important.Incorporating both activities into the same institute can help achieve a critical minimum institute size and contribute to a coherent metrology policy at the national level.
In addition, for the purposes of modern LM, the chain of metrological traceability must be provided through a continuous chain of calibrations before the final verification of compliance with legal or regulatory requirements.However, as regulated in ISO/IEC 17025 [7] , information on competent laboratory standards includes only a statement of © 2021 Measurements infrastructure compliance with a specific technical specification without the measurement results and associated uncertainties.Such information is sometimes used to spread metrological traceability [3,8,9] .
In some countries, a national standardization body may also be responsible for some metrological functions, while a national accreditation body may not exist at all, or its scope may be significantly limited.However, in all cases, NMI is an important source of expert knowledge when evaluating the performance of laboratories, particularly calibrated ones.There is no single desired model for the distribution of responsibilities between the bodies for ensuring the quality of products and services, however, the more national bodies are involved in metrological activities, the more important it is to have effective mechanisms for coordinating work [3,6] .
Traditionally, NMI almost always belonged to the public sector.However, recently, some countries have tried to give NMI a certain degree of management freedom necessary for the effective functioning of such a research organization.There are usually three main organizational forms of NMI: a state institute that owns and manages its own laboratories; a private institution operating under the direction of the government, with appropriate controls to protect fair competition and national security; and a government agency that coordinates public or private institutions.
The choice of form largely depends on the existing structures and institutions, the fields of metrology that are aimed at the development of the national metrology policy, and the constitutional and legislative traditions of the country [3] .

Activities of the NMI within the framework of the CIPM MRA
For the purposes of the CIPM MRA [2] , one national institute is usually designated as the NMI for the country, while the others act as Designated Institutes (DIs).It is important that there are adequate measures for the coordination of the activities of these institutes, in particular with regard to their contribution to BIPM, the main institute.For the calibration and measurement capabilities (CMS) [2,10,11] of an NMI (or DI) to be recognized under the CIPM MRA, usually based on international calibrations of NMI (or DI) standards [12] , the laboratory must operate a quality management system [13] .This system must meet the requirements of international standards ISO/IEC 17025 [7] or ISO 17034 [13] if the laboratory produces standard samples.The CIPM MRA does not require accreditation of NMI measurement services, although many NMIs are nationally accredited.The decision on accreditation is made by NMI or their national metrological bodies.The OIML G 1-100 (GUM) guide [14] is used to calculate the measurement uncertainty.
Reference is made to the CIPM MRA to determine whether national standards of other countries have metrological traceability.According to the CIPM MRA, such information is available in the publicly available BIPM Key Comparison Database (KCDB) [15] . in 2018 [16] .

The inclusion of relevant information in the KCDB en-
The NMI of Ukraine and the signatory of the CIPM MRA is the Ministry of Economy, whose main functions in the field of metrology are regulated by the legislation of Ukraine on metrology and metrological activities.There are four DIs operating in Ukraine, in particular the State Enterprise (SE) «Ukrmetrteststandart» (Kyiv).All DIs conduct their international activities within the framework of the CIPM MRA; in particular, they participate in the international reconciliation of national standards and in the prepara-tion of CMCs, which are subject to interregional expertise before their publication in KCDB BIPM.
Since Ukraine signed the CIPM MRA in 2003, according to information from KCDB BIPM [15] , SE «Ukrmetrteststandart» took part in a total of 75 comparisons of standards out of 146 (51 %), in which examination and were published in KCDB BIPM [15] .
The information on the number of CMC entries pub- approved within one of the regional metrological organizations that implement the requirements of the CIPM MRA according to the requirements [17] .
Representatives of SE «Ukrmetrteststandart» are observers in the Consultative Committee on the

Quantity of Matter (CCQM) and the Consultative
Committee on Electricity and Magnetism (CCEM) of the CIPM after reviewing the institute's activities in the specified fields at the meetings of the relevant consultative committees and subsequent decisions of the CIPM.

Other areas of activity of NMI
Another important function of the NMI (DI) is the responsibility for ensuring metrological traceability to national standards by providing calibration services for high-precision MIs.This should ensure international recognition of calibrations (and, therefore, tests) to avoid technical barriers to trade through participation at regional and international levels in international recognition systems managed by ILAC and/or BIPM.For NMI (DI), expert assessment and accreditation of laboratories are considered equivalent tools [3,8] .
Although accreditation is, as a rule, a voluntary system, however, the implementation of certain regulatory acts may require the accreditation of bodies responsible for assessing compliance with MIs.If NMI (DI) is involved in work related to conformity assessment in the field of LM, then such accreditation may be required.OIML issued a special international document that contains guidelines for the application of the ISO/IEC 17025 standard for the assessment of testing laboratories working in the field of LM [3,18] .
A number of NMIs participate in the OIML-CS system [19] , a system for issuing, registering, and using OIML certificates and associated OIML type assessment/test reports for MI types based on the requirements of the OIML recommendations.This system promotes global harmonisation, uniform interpretation, and implementation of legal metrological requirements for MIs and avoids unnecessary re-testing of MIs when obtaining national type assessments and approvals.NMIs, as OIML certification bodies, must demonstrate compliance with the ISO/IEC 17065 standard [20] and testing laboratorieswith the ISO/IEC 17025 standard [7] .Engineers with higher education mainly perform highly specialized tasks in science, industry or as staff in the field of legal metrology.Due to the fact that their number in the field of LM is relatively small, OIML issued a special international document on the training and qualification of LM workers [21] .In this The main goals of the International Measurement Confederation (IMEKO) [22] are to promote the international exchange of scientific and technical information in the field of measurement and instrumentation and to strengthen international cooperation between scientists and engineers in research

Summarizing the components of NMI activities and establishing their models
According to the results of the analysis of the main areas of activity of NMI (PI), the following directions characteristic of NMI (DI) can be identified: -participation in reconciliations of national standards

Conclusions
NMIs play a significant role in ensuring the effective functioning of the national metrological infra- uncertainty and field of application.Modern metrology contributes to ensuring the accuracy, reliability, comparability, and reproducibility of measurements in all spheres of social activity.It is of crucial importance for scientific progress, technological development, and the functioning of society in general and plays an important and integral role in the development of modern technologies.Important areas of impact of metrology are industry, science and research, technological development, trade, health care, environment and security, etc.
the development and support of national standards; participation in international comparisons of national standards; development of calibration methods and calibration of working standards and high-precision measuring equipment (MI); participation in international cooperation to ensure unity and standardization of measurements at the global level; national standardization to promote uniformity of metrological measurement rules; training and consulting specialists in the field of metrology to promote the development and improvement of measurement methods, etc.
sures the presumption of conformity of the standards with the requirements of metrological traceability.If such traceability cannot be established through the KCDB, the central government body of the country should establish an appropriate mechanism for the necessary access to advice on the acceptability of alternative solutions provided by the NMI.This approach is supported by the Joint Declaration on Metrological Traceability adopted by BIPM, OIML, as well as the International Laboratory Accreditation Cooperation (ILAC) and the International Organization for Standardization (ISO) initially in 2011 and reaffirmed

Fig. 2 .Fig. 1 .
Fig. 2. Information on the number of CMC entries published by the NMI of Ukraine and SE «Ukrmetrteststandart»by fields of measurement

Fig. 2 .
Fig. 2. The largest number of published CMC entries was in the fields of measurement «Quantity of Matter» (QM) -42 and «Electricity and Magnetism» (EM) -41.Publication of NMI (DI) entries is possible only if the NMI (DI) quality management system is (DIs) participate in the work of technical committees (TC) of ISO and the International Electrotechnical Commission (IEC), which develop international standards on metrology.In particular, the secretariats of national TC 90 «Instruments for measuring electrical and magnetic quantities», TC 122 «Analysis of gases, liquids and solids» and TC 156 «Instruments for measuring mass, force, deformation and mechanical tests of materials» operate in SE «Ukrmetrteststandart».These national TCs of standardization have appropriate connections with the TCs of ISO and IEC and deal with harmonization of relevant international standards at the national level.43 representatives of Ukrainian DIs participate as observers in the technical work of 17 TCs and 26 subcommittees of the OIML, thus covering almost the entire field of development of Recommendations, Documents, Guidelines, and Reports of the OIML.By order of the Cabinet of Ministers, a representative of Ukraine was appointed to the International Committee of Legal Metrology (CIML), which allows for the coordination of representation in the work of OIML at the national level.
and industry.It is a confederation of national scientific and technical societies dealing with measuring technology and related issues (instrument engineering, metrology, automation, etc.).Representatives of NMI (DI) play a significant role in the work of a large number of TC IMEKO as their members take an active part in scientific congresses and symposia of TC.One of the leading topics of the papers of scientists of the NMI (DI) is the presentation of advanced achievements in the field of measurements in various fields, the results of the creation of high-precision MIs, and the reconciliation of national standards.
; -preparation and publication of CMC entries (2); -calibration of high-precision MIs (3); -accreditation of its calibration laboratories (4); -testing and verification of MI in the legally regulated sphere (5); -participation in the development of national metrology standards (6); -training and retraining of the personnel performing calibration and verification of the MI and experts in the field of metrology (7).Depending on the characteristics of the country as a whole and the development of its industry in particular, NMI (DI) models are proposed taking into structure.They are responsible for the development and maintenance of national standards, calibration methods, and calibration of working standards and high-precision MIs.NMIs participate in international reconciliations of national standards, publish their calibration and measurement capabilities, contribute to the national standardization of metrological standards and measurement rules, and train specialists in the field of metrology.The analysis of the main modern components of NMI activity allowed to propose variants of NMI functioning models depending on the existing national metrological infrastructure.This can allow taking into account various risks of the operation of such infrastructure, taking into account the development of the national economy and society and the corresponding adaptation to modern conditions.

Table 1 .
NMI (DI) models and their characteristics account the specified types of their activities, which are listed inTable1(L -low level, M -medium level, H -high level).Model A of NMI is characterized by a high level of metrological activity in all directions and is used only in certain countries.Model В NMI (DI) is characterized by an average level of preservation of national standards, a high level of calibration works, and a high level of participation in the field of LM, which is, in particular, widespread in Ukraine.Model C is characterized by an average level of preservation of national standards and calibration works and a low level of participation in the field of LM.Model D is characterized by a low level of preservation of national standards, calibration works, and an average level of participation in the field of LM, which is common in a number of countries.Model E is characterized by a low level for all areas of metrological activity, which is characteristic of countries with the least developed economies.