The history of Euro-Asian Cooperation of National Metrological Institutions (COOMET) has already spanned three decades (12 June 1991 is considered the date of its establishment – the day when the COOMET Memorandum of Understanding was signed). COOMET is an officially recognized regional metrology organization, as well as a regional legal metrology organization. Cooperation in COOMET and its outcomes allow member countries to successfully tackle metrological issues, faced by the national economy under market globalization, as well as to ingrate in the international metrological system. A brief overview of the history of creation and results of activity of COOMET is provided. The effectiveness of cooperation is evaluated, the promising areas of COOMET's activities are outlined.

The article considers the necessity of ways of modernization the Primary standard of the temperature GET 34-2007. Special attention is paid to the transition to a new defi nition of kelvin. Taking into account that the new defi nition of kelvin does not directly affect the status of the current international temperature scales ITS-90 and PLTS-2000, but there are significant advantages for measuring thermodynamic temperatures below 20 K and above ~1300 K, the main focus of the modernization of the GET 34-2007 in the range from 273.15 K to 1235 K was focused on improving the methods and means of implementing the International Temperature Scale ITS-90. As part of the modernization of the Primary standard in the range above 1235 K, a set of equipment has been created that allows the reproduction of kelvin in accordance with its new definition by two methods recommended by the Consultative Committee: the method of absolute primary radiometric thermometry and the method of relative primary radiometric thermometry. The basic principles of the implementation of these methods, composition and metrological characteristics of the Primary standard are described. The results of key comparisons of the developed standard in the range from 273.16 K to 692.477 K and the results of temperature measurements of a number of high-temperature fi xed points and a comparison of the results with the published results of leading national metrological institutes are presented.

The history of the creation of the State primary standard of gas volumetric and mass flow rate units GET 118-2017 is presented. The significant role of international comparisons was noted at various stages of the creation of GET 118-2017: the comparisons results confirmed and made it possible to include in the KCDB the calibration and measurement capabilities of the Russian Federation in the field of gas volumetric flow measurements, and also helped to determine the direction and list of measures to improve the standard. A patented comparison method for calibrating critical nozzles, implemented in GET 118-2017 for transfer the units of volumetric and mass flow rates of gas to working standards, is described. The design, composition and characteristics of GET 118-2017 are presented. Currently, more than 700 working standards of gas volumetric and mass flow rates used in the Russian Federation and some KOOMET member countries are traced to GET 118-2017, the total number of calls to GET 118-2017 for the transfer of measurement units exceeds 3500 per year.

Considered options for automating the calibration. An automatic calibration system has been developed, investigated and introduced into the production process, which is a software and hardware complex consisting of measuring instruments from the composition of the National standard of voltage unit – volt and additional modules. The automatic system was created on the basis of the modern programming language “Python” with the involvement of the experience of metrologists. A study of the results of calibration of reference voltage measures was carried out: the obtained results of the calibration of the DC voltage (assigned real value with expanded uncertainty) were analyzed in automatic and manual modes and using the “supraVOLTcontrol” system, which implements the Josephson effect. The automatic system was used in the study of the integral instability (nonlinearity) of a digital voltmeter, while a signifi cant minimization of labor costs was obtained. The developed automatic calibration system allows to reduce labor intensity and duration of measurements, provides fl exibility and ability to rebuild depending on emerging issues during research.

In the context of the needs of the leading sectors of the world economy, the current state of metrological support for measuring units of mass and volume of a liquid in a flow, mass and volume flow rates of a liquid in the range of micro-flow rates of 10^–5–10³ ml/min is considered. Based on the results of the analytical review, the main metrological and operating characteristics of national standards are presented. The basic principles of generating a fluid flow in national gravimetric and volumetric standards when measuring the mass and volume of a fluid by the dynamic weighing method have been determined. Constructive solutions and principles of operation of key modules of national standards are considered. Methods for filling a liquid into a storage tank and designs of storage tanks are determined, taking into account the minimization of the effect of liquid evaporation, the influence of capillary force and buoyancy. The main sources of uncertainty in measuring the mass and volume of a liquid by the dynamic weighing method and methods for minimizing these uncertainties are considered. A modified model of dynamic measurement of liquid mass flow rate is proposed, taking into account the main sources of uncertainty. A comparative assessment of the influence of sources of uncertainty on the metrological characteristics of national standards is presented.

The consistency of the results of international comparisons and the equivalence of national standards, improvement of methods for the realization of the International Temperature Scale ITS-90 main fixed points of metals freezing are considered. Two sources of uncertainty of the temperature value during realization of metals freezing fi xed points have been determined. Experiments on the initiation of the inner interface between the liquid and solid phases of the metal have been carried out, the effect of the initiation conditions on the interface structure and measured temperature value in aluminum and indium fixed points cells has been investigated. The question of the correctness of the impurities influence estimates according to the laws for the only outer interface moving from the crucible walls to its center is considered. Analysis of the freezing curves obtained under different initiation conditions allowed determining the criterion for the presence of a continuous inner interface and the conditions for the formation of a single outer interface during slow crystallization of the metal without the formation of an inner interface. The obtained criteria willallow metrological institutes to choose the correct conditions for the initiation of the inner interface when using different designs of cells and heaters.

One of the tasks of the COOMET 786/RU/19 pilot comparisons is to check the correctness of the hydrophone model proposed in VNIIFTRI, consisting of an advance line and a minimum-phase part, including the effect of sound diffraction and resonance properties of the active element. This model makes it possible to use the Hilbert transform to obtain the phase-frequency response from the amplitude-frequency response as well as for inverse operation. The results of measuring experiments performed using facilities of the State Primary Standard GET 55-2017 are presented. For many practical tasks, it is not necessary to obtain the phase-frequency response for an acoustic center of the receiver. It is enough to determine the shape of the phase-frequency response using much less laborious methods. The question of which of the characteristics is expedient to determine during calibration - for an acoustic center, or for a point on the surface of an active element, deserves a discussion among specialists performing acoustic measurements.

The issues of increasing the accuracy of determining the average energy and the type of energy distribution (shape of the spectrum) of neutrons from Sb-Be- and Ra-Be-sources are considered. The indicated photoneutron sources are used to calibrate the energy scales of neutron spectrometers and to determine the energy dependence of the sensitivity of radiometers and neutron dosimeters. A method is proposed for calculating the energy spectra of radionuclide neutron sources of the Sb-Be (γ, n) and Ra-Be (γ, n) types, and the calculation results are presented. The dependence of the spectrum of the source on its design is investigated. The correctness of the results of calculating the energy spectra of radionuclide sources has been confi rmed experimentally. The data obtained will be used to determine the energy dependence of the sensitivity of neutron spectrometers, radiometers and dosimeters.

Precision interference measurement of parameters of form optical surfaces are one of the most important type of the measurement in the field of the geometrical values. In countries-participants of this comparisons the special primary standards in this field of measurements take part in reproduction and transmission the unit of length in this field of measurements ensuring high measuring and calibrating capabilities countries in this type of measurement. In this article presents the result of supplementary comparisons COOMET 570/UA-a/12. The result of comparisons allowed to declare to Belarus and Russia, and to confirm to Ukraine their measuring and calibrating capability in database CIPM MRA.

The most challenging goals in the field of chemico- and bioanalytical measurements are described. Solutions of these problems are presented, which are being solved in particular by participating in new international comparisons organized by the Cosultative Committee on the Amount of Substance of the International Committee on Weights and Measures (CCQM CIPM). The purposes and tasks of developing key comparisons in the following areas are described: isotopic measurements; determination of the purity of substances; organic analysis; bioanalytical measurements; measurements of aerosol particle parameters; measurements in the field of gas analysis and electrochemistry. It is shown that participation in international key comparisons makes it possible to obtain valid and reliable results of measurements of the composition and properties of gas and liquid media, as well as solid substances and materials.