ABSTRACT. Bulgarian Institute of Metrology (BIM) performing its duties as Bulgarian National Metrology Institute and National Legal Metrology Body has a key role in metrology infrastructure. The main activities of BIM support the quality of life and the development of the economy. This is done by providing metrological traceability for national measurements using national standards and certified reference materials that BIM develops and maintains, and also with metrological control activities on measuring instruments related to health, public safety, environmental protection environment, state and municipal receivables and trade payments.

ABSTRACT. Recently, the challenges of the digital industry have become extremely urgent. One of the confirming facts is the renaming of the Ministry of Telecom and Mass Communications of the Russian Federation to the Ministry of Digital Development, Communications and Mass Media. World digital industry ideologist - Emerson Corporation (USA) - identifies four main components of digital industry.

As a typical example of digital industry, the report considers the sheet rolling shop of the Magnitogorsk Iron and Steel Works. The first problem is equipment reliability and reduction of downtime and repair time due to fairly frequent breakdowns. The second problem is the quality of rolled products and its relation with the state of the process equipment. The main technological devices are electric and electro-hydraulic drives, rolls and support plate, which determines their axial movement.

The most important parameter of the technological process is the force created by the power elements. It is measured by pressure sensors installed in electrohydraulic actuators. Another important factor of the technological process is the deformation uniformity of the rolled band. It is controlled during processing by strain gauges. It is also necessary to measure the temperature, which is carried out by thermocouples. An important factor is also the vibrations level in mechanical gears and some other elements.

The report analyzes the application of these approaches in the task of applying the digital industry concept in this technological process.

ABSTRACT. The Guide to the Expression of Uncertainty in Measurement (GUM) recommends using the so-called Type A method to calculate the standard uncertainty associated with the best estimate of a quantity measured under repeatability conditions. Instead, for quantities about which other forms of information are available, the GUM says that Type B methods of evaluation should be used. The former method is based on the frequentist interpretation of probability, while the latter involves essentially the Bayesian theory. This mixing of concepts is not convenient, as it leads to the GUM being inconsistent. For this (and other) reasons, a draft for a major revision of the GUM was prepared. Perhaps the greatest modification introduced in this draft with respect to the GUM had to do precisely with a new (Bayesian) method to obtain the uncertainty of a quantity for which more than three repeated indications are available. Had this draft been accepted, the revised GUM would have become consistent. In the present article, the fundamentals of the current and proposed Type A evaluation methods are reviewed. A brief explanation of why the proposed draft was not accepted is given also.

ABSTRACT. The nonlinearity of the transfer function of the analog-to-digital converter (ADC) is one of the most important sources of measurement error of parameters of electrical grids. This is due to the fact that the ADC nonlinearity can be compensated only as a result of individual adjustment of the measurement channel. This approach results to a significant increase in the cost of the measurement device and is not applicable for commercially available measurement devices. The nonlinearity of the ADC conversion function results to errors of the signal samples and, as a result, to the errors of the complex spectrum. The curve of nonlinearity of the most successive approximation register (SAR) ADCs is close to a pseudo-random and can be approximated by a random function. The paper considers an approach to approximating the ADC nonlinearity by a random function and estimation of the measurement error of the amplitude spectrum for such a representation of ADC nonlinearity. The considerate method is compared with the “worst case” method. Analytical expressions, that allows to estimate the measurement error of the amplitude spectrum for a given ADC integral nonlinearity and the sampling frequency are obtained. The simulation modeling is completed in Matlab software.

ABSTRACT. The closed loop transducers (also called compensation or zero flux transducers) have an integrated compensation circuit by which the performance of the current transducers using the Hall effect can be markedly improved.

The range of the closed loop transducers permits measurement of IPN nominal currents from a few amperes to several tens of kA, with an accuracy of about 1 %. With the devices produced by DynAmp subsidiary, which use the same technology, it is possible to measure very high currents up to 500 000 A. The closed loop transducers are capable of measuring DC, AC and complex waveform currents with galvanic isolation.

They stand out by their: - Excellent accuracy. - Very good linearity. - Low temperature drift. - Very fast response time and wide frequency bandwidth. - They do not produce any insertion losses in the circuit to be measured.

Closed loop current transducers are used in a number of industrial applications, where they provide the measurement, display and control of currents. Among typical applications are the following: - Frequency converters and three-phase drives - Converters for servo-motors frequently used in robotics. - Electric welding equipment - UPS and other equipment operating with batteries - Electric vehicles - Electric traction systems - Converters for windmills. - Special power supplies for radars. - Energy management systems, switching power supplies, lasers, rectifiers for electrolysis. - for laboratories or for test and control benches.

ABSTRACT. За електрическите съоръжения от съществен интерес е хармоничния състав на експлоатационното напрежение. Неговото измерване и контрол се извършва чрез анализатори на електрическа енергия (АЕЕ), които подлежат на метрологичен контрол – калибриране. В метрологичната практика при калибриране на АЕЕ по хармоничен състав на напрежение за еталон се използва калибратор - генератор на синусоидални (два и повече) сигнали. Предложен е нов подход – калибриране с използване на периодичен правоъгълен импулсен двуполярен сигнал, при който еталон е калибратор на периодичен импулсен сигнал. В публикацията се представят резултати от калибриране на АЕЕ Fluke 435 по хармоничен състав на напрежение с използване на двата подхода - подходът на синусоидалния (синусоидалните) сигнал и подходът на периодичния правоъгълен импулсен сигнал. Сравняването на резултатите показва приложимост и целесъобразност от използване на подхода с периодичния правоъгълен сигнал при калибриране на АЕЕ по хармоничен състав на напрежение в метрологичната практика.

ABSTRACT. The paper concerns the applicability of the precise calculation of the resistances in an earthing system using the clamp-on method for contactless measurement of resistance. The importance of the calculative method application is evident in the critical cases of a system with only few (near three) earthing points. The paper bases on previous results obtained for the method of independent calculation of each separate earth resistance based on the results from direct clamp-on measurements.

ABSTRACT. Estimation of the Uncertainty of Measured Efficiency of Electrical Vehicle Charging Stations

ABSTRACT. Synthesis and analysis of the results of evaluation of metrological characteristics of VEGA UKS collimating stands, carried out by VNIIM specialists. Observation of VNIIM standard units facilities, employed in establishing traceability of collimating stands to primary standard of flat angle unit. Consideration of major factors, affecting the measurement process.

ABSTRACT. The results of measuring the spectral diffuse reflectance and spectral radiance factor of white, gray, black and color reference materials in various geometries of measurement are presented. Their colorimetric characteristics are defined. Their color differences are rated. The study was conducted with three different spectrophotometers in the visible range of the optical spectrum.

ABSTRACT. The traceability of National vibration measurement standard is achieved through periodic calibration check by determination of the magnitude of the complex sensitivity Sq of a standard accelerometer type B&K 8305(BB) via the Initial calibration method based on Laser Interferometry. Harmonic sinusoidal vibration is applied to the accelerometer and its amplitude is measured with laser interferometer according to ISO 16063-11(Method#3: Sine wave-approximation). The obtained results are compared with their previously measured values from past PTB calibration report, in order to assure its stability and quality of operation.

ABSTRACT. With the introduction of the new definition of the kilogram, the last definition of a base unit based on a physical artefact is sent to history. This change will not affect directly the life of ordinary citizens, but it will have a huge impact on the work of the National Metrological Institutes (NMI) in the long term, and on the Bulgarian Institute of Metrology (BIM) including.

ABSTRACT. The report addresses the method and tools to perform verification of differential pressure transmitters with DC output signal, Metran 22, DD-2440 model, with square root function and computation of the functional relationship between input and output signal. The aim is to detect the compliance between the normalized and measured characteristics in the process of verification of the characteristics.

ABSTRACT. В доклада са представени основните задачи на метрологичното осигуряване на дозиметър-радиометър тип УИМ 2-2 в “АЕЦ Козлодуй” ЕАД, дейностите, които се извършват за да се осигури очакваното високо качество в тази област и съответствието с националните и международни изисквания. Докладът се основава на разработени и утвърдени по установения ред документи от Лаборатория “Измерване на йонизиращи лъчения” към отдел “Метрологично осигуряване” в “АЕЦ Козлодуй” ЕАД, базиращи се на натрупания дългогодишен опит и отговарящи на нормативните и законови изисквания.

ABSTRACT. At Temperature Measurements Department of the National Center of Metrology, BIM the standard in the field of calibration of relative humidity is a Precision Dew Point Hygrometer, which is included in an Automatic Relative Humidity Calibration System with temperature camera and flow type generation of the moisture gas. Review of relative humidity (RH) measurements requires: - Traceability of reference standards - The inputs with known contribution to uncertainty - Validated procedures - Uniformity of the chamber environment - Multiple RH and temperature calibration points Calibration and Measurements Capabilities (CMC’s) for Relative Humidity of Temperature Measurements Department, National Center of Metrology (NCM), BIM were adopted in 2016 and in 2017 they were published in Appendix C of the KCDB. A brief review and description of the measurement techniques, apparatus used and important points of uncertainty budget are given in this paper.

ABSTRACT. In this article, the area method is proposed for determining the time constant and damp constant of an accelerometer when analyzing its gain-frequency characteristic. The systematic errors of determining the time constant and the damp constant by the proposed method are investigated, and the ways to reduce them are considered. Standard uncertainties of the constant time and the damp constant are estimated, ways of optimizing a measuring experiment to reduce them are proposed. Recommendations on the practical application of the proposed method are given.

ABSTRACT. The aim of the paper is to present sensors for measuring the ground motion and a specific application related to recording seismic events on Livingston Island. The theory of operation of seismic sensors (seismometers) is described briefly. The basic parameters, classification and dynamic behavior of a seismograph system are discussed. It is considered the force-balance principle for constructing nowadays seismometers. Some of the requirements for site selection and installation of seismometer are also commented on. Bulgarian broadband seismological station (with international abbreviation LIVV) is established on 19.12.2015 near the Bulgarian Antarctic Base “St. Kliment Ohridski” on Livingston Island as a seasonal station. The deployment period of the station comprises three Antarctic campaigns in the period 2015-2018. More than 12000 tectonic an ice generated events were recorded. The seismological equipment operates in harsh weather conditions with low temperatures, strong wind gusts and high humidity. In order to ensure optimal operation of the seismic station, special precautions are taken during the installation of the apparatus. The paper presents the assessment of the performance of the seismological equipment, power supply, data transfer solutions and technical problems met during the operational

ABSTRACT. The authors of the article reviewed the methods of researching the formation of the sound field of a room using examples from audience halls for various purposes. The task of forming the optimal acoustic conditions in the rooms of the audience halls was formulated, objective and, related to them, subjective indicators of the room acoustic quality were described, the characteristics of the indicators were indicated. The authors proposed the stages of the acoustic examination of the premises, which include: - the stage of checking the existing architectural building solutions of the interior surfaces of the room, in order to identify the surfaces focusing sound rays (which reduce the diffuseness of the field), and also to obtain the frequency dependence of the reverberation time and to compare with the optimal reverberation time; - the stage of the development of the recommendations to increase the diffusivity of the sound field and to ensure the optimal structure of the reverberation process (the stage of creating a specification for the design of enclosing surfaces); - the stage of the acoustic modeling of premises with recommended finishing materials and enclosing surfaces recommended in a technical task; - the final stage, which allows to take measurements of the characteristics of an existing sound field in a room after all construction and finishing works using the hardware-software complex. The authors of the article present the results of performing each of the stages of acoustic examination using the existing software and software modules developed by the authors, the proposed hardware and software module. The results of the implementation of all stages of acoustic expertise obtained by the authors allow to conduct a comprehensive assessment of the sound field generated in the premises, taking into account the peculiarities of musical and speech materials in the audience halls. The approbation of the measurement methodology was carried out on the basis of the design documentation made for the already existing halls of Ukraine and the near abroad, for which the recommendations of all the stages of acoustic expertise during construction and finishing works were taken into account.

ABSTRACT. The main focus in this paper that is presented is towards developed vibration test system solutions.

ABSTRACT. Since 1998 SPECTRI LTD focus has been sound and vibration till today. With the development of new technologies in that field, we are trying to adapt, learn, evolve so we can do our work better, accurate and correct to our customers. By becoming partners with world leading companies in the last year we are able to achieve that. In the recent paper a comparative information for the progress, development, news and products in the field of noise and vibrations by SPECTRI Ltd. is presented.

ABSTRACT. This paper presents the used concept, technical support and metrological reference regarding the unique accredited laboratory for calibration of sound level meters, calibrators, multifunctional calibrators, noise dosimeters - SPECTRI - LAB in the Republic of Bulgaria. Presenting SPECTRI – LAB calibration system and methods of applying methodologies and international standards.

ABSTRACT. In the recent paper a general information about the new partnership from Brüel & Kjaer Vibro with Spectri is presented. Brüel & Kjær Vibro is the world’s leading independent supplier of protective/safety monitoring, and knowledge-based condition and performance monitoring solutions forrotating machinery. Their solutions, incorporating a wide product range and global service organisation, are tailored to maximize safety, plant utilization and operational effectiveness, while minimizing unplanned outages and maintenance costs. By becoming partners with them, we can provide the Bulgarian industry with new online/offline solutions for machine protection, condition monitoring, diagnosis, vibration measuring equipment, sensors, accessories.