Precision active power measuring channel

The article is devoted to increasing the reliability, noise protection and improving the metrological characteristics of active power measuring converters. Much attention is paid to the problem of developing effective methods for constructing structural diagrams of active power measuring converters. This is explained by the growing requirements for the basic metrological characteristics of active power measuring converters as elements of information – measuring systems. The main attention in the work is paid to the development of ways to correct the influence of destabilizing factors in working conditions. The undoubted advantage of the work is a thorough analysis of the instrumental errors of the measuring channel, the original means of correction of the phase error and the error due to the limited suppression coefficients of in-phase interference. The obtained simulation results in the Electronics Workbench environment made it possible to determine the most effective way to protect against interference.

Minimization of errors in discrete wavelet filtering of signals during ultrasonic measurements and testing

Error minimizing methods for discrete wavelet filtering of ultrasonic meter signals are considered. For this purpose, special model signals containing various measuring pulses are generated. The psi function of the Daubechies 28 wavelet is used to generate the pulses. Noise is added to the generated pulses. A comparative analysis of the two filtering algorithms is performed. The first algorithm is to limit the amount of detail of the wavelet decomposition coefficients in relation to signal interference. The minimum value of the root mean square error of wavelet decomposition signal deviation which is restored at each level from the initial signal without noise is determined. The second algorithm uses a separate threshold for each level of wavelet decomposition to limit the magnitude of the detail coefficients that are proportional to the standard deviation. Like in the first algorithm, the task is to determine the level of wavelet decomposition at which the minimum standard error is achieved. A feature of both algorithms is an expanded base of discrete wavelets ‒ families of Biorthogonal, Coiflet, Daubechies, Discrete Meyer, Haar, Reverse Biorthogonal, Symlets (106 in total) and threshold functions garotte, garrote, greater, hard, less, soft (6 in total). The model function uses random variables in both algorithms, so the averaging base is used to obtain stable results. Given features of algorithm construction allowed to reveal efficiency of ultrasonic signal filtering on the first algorithm presented in the form of oscilloscopic images. The use of a separate threshold for limiting the number of detail coefficients for each level of discrete wavelet decomposition using the given wavelet base and threshold functions has reduced the filtering error.

Analysis of the temperature component of the combined standard uncertainty of the refractive index according to the test data of the control system for meteorological parameters developed for the Lyptsi geodetic polygon

The National Scientific Centre “Institute of Metrology” is actively involved in the implementation of a number of international projects under the EMPIR programme. One of such joint projects is the EMPIR 18SIB01 GeoMetre research project “Large-scale dimensional measurements for geodesy”. The overall goal of the project is to ensure traceability of length measurements – from the measurement standard of the unit of length to long distances typical for geodetic measurements. As a result of the project, it is necessary to provide length measurements of at least 5 km with an expanded uncertainty of no more than 1 mm. The main task of the NSC “Institute of Metrology” within this project is the development, research and practical implementation of methods and means of accounting for the influence of the earth’s atmosphere on the results of measurements of long distances in geodesy, carried out using electromagnetic waves in the optical range. When performing the section Task 1.4 of the project, new methods of highly accurate determination of the mean integral refractive index of air, used as a correction taking into account the influence of the atmosphere on the measurement results, are justified. Requirements for the accuracy of measurements of meteorological parameters at discrete points of the baseline are formulated, which are necessary to determine the mean integral refractive index. That is, the requirements for the metrological characteristics of temperature, pressure and humidity sensors are determined. The article discusses the results of the development, manufacture and testing of the sensors for temperature measurement. It is shown that the created sensors meet the requirements of the GeoMetre project.

Reduction of the auto seismic component of error of a ballistic laser gravimeter by excitation of an induction-dynamic catapult from an AC voltage source

The purpose of the study is to analyse the influence of the excitation of an induction-dynamic catapult of a ballistic laser gravimeter from an AC voltage source at different frequencies on electromechanical indicators that provide a reduced value of the auto seismic component of error in measuring the gravitational acceleration g due to a decrease in the recoil force. A mathematical model of the gravimeter catapult when excited from an AC voltage source is proposed, taking into account the interrelated electrical, magnetic and mechanical processes. The nature of the electromechanical processes in the catapult of the gravimeter with such excitation has been established. It is shown that a phase shift occurs between the currents in active elements, as a result of which positive (repulsive) pulses of the electrodynamic force alternate with negative (attractive) pulses of force. A criterion for the efficiency of the gravimeter catapult has been introduced, taking into account the maximum value of push of the test body at the smallest values of the electrodynamic force and current of the inductor winding. It was found that the highest efficiency of the gravimeter catapult is provided at a frequency of 250 Hz, at which the catapult efficiency is 3.5 times higher than at a frequency of 50 Hz. It is shown that the transition from the method of excitation of an induction-dynamic catapult with one short pulse to excitation from an AC voltage source makes it possible to reduce the uncertainty in measuring the gravitational acceleration.

Measurement of microwave radiation pressure on thin metal fibers

The pressure of electromagnetic radiation in the optical range is widely used to hold microparticles in a given place and control their movement. This is possible by focusing the laser radiation into an area with the dimension of several micrometers. The intensity of radiation in this area is large and sufficient to retain micro-particles in the laser beam and manipulate them. Nowadays, intensive research is underway on the use of microwave and terahertz radiation and the possibility of applying radiation pressure in these ranges. But in the microwave range, the focal spot dimension is much larger than in the optical one. Therefore, control of the objects whose dimensions are comparable to those of the focal spot using the radiation pressure requires very high power. For the objects with small dimensions, a small amount of radiation energy falls on them, and the acting force decreases. However, it is known that thin conductive fibers interact very strongly with microwave radiation. This can be used to levitate short thin metal fibers (vibrators), hold them in predicted place and control their position in space. The paper describes the measurements of the pressure of microwave radiation with a wavelength of 8 mm on thin copper fibers. Torsional balance is used for this purpose. In the metal case on a suspension from a tungsten fiber with a diameter of 8 microns there is located the rocker arm with 50 mm length with receiving elements in the form of system of copper fibers with a diameter of 300 microns and 15 mm length. Microwave radiation was directed to one of the receiving elements using a horn. The calibration of torsion balance, the measurement process, and the evaluation of the resulting error are described. The measurements gave the value of the efficiency factor of the radiation pressure Qpr = 4.86. This agrees satisfactorily with the results of calculations Qpr = 5.39. The difference is 10%.

Application of systems thinking to the establishment of metrological traceability chains

International agreements in the field of metrology and accreditation of calibration laboratories are the basis for establishing global metrological traceability. Important elements of metrological traceability are calibration of measurement standards and measuring instruments, assessment of measurement uncertainty. The International Laboratory Accreditation Cooperation has a specific policy regarding on traceability of measurement results and estimation of measurement uncertainty in calibration. The partial concept diagram around metrological traceability in accordance with the International Vocabulary of Metrology is proposed. This diagram contains a total of nine metrological concepts, which have most of the associative relations. There are associative relations between the concept of metrological traceability chain and concepts of metrological traceability, measurement standard, calibration and calibration hierarchy, and through the concept of measurement standard with the concept of measurement uncertainty. Systems thinking to the analysis of state of proposed terminological system around metrological traceability was applied. For construction of generalized metrological traceability chain, all the established properties of the system elements around the terminology system of metrological traceability were taken into account. Generalized metrological traceability chain for different levels of the calibration hierarchy was proposed. The proposed chain can be used to develop appropriate chains for specific areas of measurement. To achieve this, it is necessary to determine the specific measured value, the required measurement uncertainty for different levels of the calibration hierarchy and select the necessary measurement standards. Such schemes should be used in national metrology institutes and calibration laboratories.

Ensuring the validity of the results of calibrations and tests by statistical methods

According to the requirements of ISO/IEC 17025:2017, the validity of test and calibration results is ensured, inter alia, by intralaboratory check of the results obtained. In this case, it is preferable to use statistical methods. The ISO 5725 standards define a number of such methods, but the choice of specific methods is left to the laboratory, taking into account the requirements for the adequacy of the effort, resources and time for the purposes of the work performed and the risks of obtaining inappropriate results. In this case, the laboratory itself must in a certain way determine which objects of calibrations (tests) should be predominantly used in checks and what frequency of checks should be foreseen. In connection with the increase in the accuracy and complexity of measuring systems, the need to apply the methods of the theory of random processes becomes more and more obvious. It is shown that the use of the Poincaré plot makes it possible to comprehensively, effectively and visually evaluate changes in the measuring process from the point of view of the dynamics of the obtained measurement results. The results of the check, in particular, the intermediate precision, make it possible to obtain a more realistic evaluation of measurement uncertainty in accordance with ISO 21748. The paper analyses some practical approaches (of varying degrees of complexity) to intralaboratory checks of the validity of calibration (test) results.

Intrinsic background of the beta channel of the aerosol volumetric activity monitor

The work is devoted to the study of the features of generation of the intrinsic background of the measuring beta channel of the aerosol monitor in real conditions of measuring the volumetric activity of aerosols, caused by radionuclides of technogenic origin. The influence of external factors on the generation of the level of the intrinsic background of the measuring channel of the monitor and its metrological characteristics is investigated. The reliability of the results of measurements of the volumetric activity of air aerosols substantially depends on the correct accounting of external factors, parameters of the monitored environment and the specified operating mode of the monitor. Aerosol volumetric activity monitors, as a rule, operate in a continuous mode, in which the aspiration method of aerosol accumulation is implemented, followed by measuring the volumetric activity of aerosols by alpha radiation and (or) beta radiation generated by technogenic radionuclides. This article describes the results of experiments on measuring the iCAM aerosol monitor’s intrinsic beta channel background under real operating conditions, and its dependence on external factors. The studies were carried out on iCAM aerosol monitors (iCAM/D and iCAM/MF modifications) manufactured by Canberra Industries Inc. in a laboratory room in normal climatic conditions with a radon volumetric activity of 35±10 Bq·m-3 and an equivalent dose rate of gamma radiation of 0.13±0.02 μSv·h-1. In modern aerosol monitors, software and hardware solutions are implemented that allow to significantly reduce the background level and, as a result, to expand the measurement range of the volumetric activity of aerosols towards low values.

Method for the numerical evaluation of the color rendering quality of matrix photodetectors

To objectively evaluate the color image of an architectural object when changing its spectral quality and luminance in lighting, it is necessary to ensure its accurate fixation. The measurement of the color coordinates of an object provides the fully capture of its appearance, but this does not allow to get an adequate evaluation of the visual impression without visualizing the lighting scene. This requires a thorough procedure of reproducing the same color coordinates for each point of the image and the object with the same angular coordinates. In this work, an attempt is made to develop a numerical criterion for evaluating the quality of color rendering of the camera as a fixer of color visual impression of the selected scene. The development of a numerical detailed method for evaluation of the quality of color rendering of cameras will allow capturing more reliably such a subjective concept as the correspondence of the visual impression of the real scene and the image file of this scene. The digital format, which contains information about the object, avoids the problems associated with aging of the image. The proposed method of developing ways to numerically evaluate color distortion in photography is considered on the example of digital cameras Nikon D300s, Sony DSC-H5. The described approach for the case of known spectral characteristics allows to unambiguously link the calculated reaction of the camera with the chromaticity coordinates of spectrally pure colors. Modern methods of evaluating the quality of light sources (IES TM-30-15) allow evaluation of the direction of the shift. The proposed indicator – graph E (λi) numerically characterizes the difference between the reaction of the camera and the reaction of the human eye and does not give an idea in which direction there is a difference, conditionally red or blue image compared to the natural scene, but is the simplest and most understandable to the untrained user. It is shown that with an accuracy of measuring spectral characteristics of 1% for the considered example with Nikon D300s, this indicator at different wavelengths is calculated with an uncertainty of not more than 0.002.

Informational uncertainty of measuring instruments

Recently, there has been a revival of interest in the use of the information approach in the theory of measurements. Unlike the traditional approach, information theory does not evaluate error or uncertainty, but entropy and the amount of information. This article analyzes a number of recent publications that develop ideas for the information approach. The limitations and disadvantages of both the entropy approach and the concept of uncertainty are indicated. As a compromise solution, it is proposed to use a criterion based on the Bongard’s uncertainty and useful information. The concept of information uncertainty is proposed, which is estimated by the amount of negative useful information, that is, misinformation introduced by the measuring instrument. Some methods for calculating information uncertainty are described. The problems of using the uncertainty approach are noted. This approach does not imply the use of such a generalized characteristic of measuring instruments as an accuracy class. The article proposes an analogue of the accuracy class in the form of relative informational uncertainty, expressed as a percentage. This will make it possible to evaluate the quality of the measuring instrument by a single parameter, the calculation of which requires a minimum of computational operations.