A computerized contact (vertical) interferometer developed at the Moscow State University of Technology “STANKIN” and based on the Uversky interferometer is described. The computerized interferometer with a resolution of 1 nm is designed for automated calibration of gauge blocks of 0, 1, 2 ISO tolerance grades with 0.1–100 mm nominal length range. Computerization of the Uversky interferometer significantly increases the calibration procedure efficiency, but at the same time causes an additional measurement error due to digital camera aberrations. A method and algorithm for computer aided correction of this error is proposed. The correction is provided by digital processing of the image from the video camera. The method is based on approximation of experimental data by polynomials of one variable of various degrees.

It experimentally confirms the effectiveness of the method by its application to the computerized Uversky contact interferometer. The advantages of the method include ease of implementation in the form of a computer program and the ability to quickly transform one-dimensional algorithms and programs for polynomials of two or three variables. The results of the proposed work are useful in improving the accuracy of measurement software for computerized interferometers and other optical mechanical measuring devices.

Mathematical models describing the propagation of monochromatic radiation in biological tissues are considered. It is shown that existing models for assessing the level of blood oxygen saturation in transmitted light do not adequately describe the processes of interaction of optical radiation with biological tissue, do not take into account the absorption capacity of those blood fractions that do not participate in the transportation of oxygen, and, therefore, the obtained results are characterized by low accuracy. A mathematical model for assessing the level of fractional blood saturation by the photometric method in transmitted light using four sources of optical radiation with central wavelengths of 660, 805, 880 and 940 nm is developed. The principle of selection of spectral characteristics of artificial radiation sources is described. The structural and functional diagram of the device for assessing the level of fractional blood saturation is presented, and the principles of its operation are outlined. Using the prototype of the proposed device and an existing pulse oximeter, the levels of fractional blood saturation of 30 subjects were experimentally estimated. The results are presented showing a decrease in the relative error by 0.71 % compared to the certified device, which proves the effectiveness of the proposed prototype device. The obtained results relate to the field of medical technology and will be useful in designing devices for non-invasive diagnostics of physiological health indicators.

The article considers the identification of spatial distributions of laser beam intensity, which is of significant practical importance for laser developers when certifying radiation sources. As an identification parameter, a measure of similarity of the measured axisymmetric distributions of laser radiation intensity with a given Gaussian distribution is proposed and investigated. To determine this measure, it is not necessary to first find the beam width at the waist. A mathematical apparatus for identification based on the use of cumulants of spatial intensity distributions is developed. A feature of the method is a limited number of cumulants of the Gaussian distribution, which makes it attractive for practical application. A comparative analysis of a number of two-dimensional distributions with a Gaussian distribution is carried out and it is shown that even with a small number of measured cumulants, high sensitivity of the method to the shapes of intensity distributions is ensured. A similarity measure for continuous one- dimensional intensity distributions of arbitrary shape is presented. The asymmetry measure of two-dimensional spatial distributions of laser beam intensity based on the ratio of moments and cumulants of the fourth and second orders is considered. The proposed measure of similarity of the measured axisymmetric intensity distributions with the Gaussian distribution is an alternative to the well-known propagation coefficient M 2 and can be used together with this coefficient.

The velocity profiles in gravity and pressure channels of flow diverters in reference installations in the field of liquid flow and quantity measurements are studied. The design shortcomings of reference installations that do not allow obtaining a flow velocity profile close to uniform in the sections of pressure nozzles over a long period of reference installation operation are described. It is shown that the placement of various straightening devices in the profiled channels and pressure nozzles of flow diverters of reference installations does not lead to obtaining a flow velocity profile close to uniform. An approach to profiling the gravity channel of the flow diverter is proposed, which allows obtaining a velocity profile close to uniform. An experimental justification of the hydraulic efficiency of the geometry of the flow part of the profiled channel of the flow diverter of the EU-3 reference installation from the State Primary Special Standard of Units of Mass and Volume of Liquid in a Flow, Mass and Volume Flow Rates of Liquid GET 63-2019 is presented. The influence of the flow velocity profile shape in the section of the profiled channel of the flow switch and the stability of the main hydro- and thermodynamic parameters of the water flow (flow rate, absolute pressure and temperature) in the pressure pipeline on the metrological characteristics of the reference installation is substantiated. Experimental studies of the velocity profile of the free-flow water flow in the section of the profiled channel are performed using high-speed total pressure meters and Pitot tubes. Close to uniform water flow velocity profiles in the section of a profiled channel were obtained for free flow in the range of investigated Reynolds numbers Re=(35...300)·103. The results of maintaining the stability of the specified value of the mass flow rate of water over a long period of time are presented. The equations for calculating the mass of water during transient processes are written down, taking into account the change in the thickness of the water flow and flow rate from zero to specified values. The presented approach and the obtained results are useful for manufacturers of reference installations and are relevant in the design, creation and modernization of profiled channels of flow switches of reference installations.

The necessity of monitoring the linear electrical parameters of cables for intrinsically safe applications is described and it is indicated that the manufacturer or supplier of cables must ensure that the cable parameters comply with current standards. The problem of unproductive consumption of cable products during its control is considered. It is noted that standard measurement methods for such a linear parameter as inductance are correct when using cable samples, the length of which is much shorter than the construction lengths. An analytical model of a cable line as an electrical facility with distributed parameters is investigated. The reason for the introduction of a limit on the length of the cable is shown, caused by the transition from a complete to a simplified model traditionally used in some standards.
A systematic method for measuring the linear parameters of cables is proposed, based on an unconventional – reverse – solution, which consists in switching from the measured secondary parameters to the calculation of primary parameters. In this case, the secondary parameters are measured in accordance with the well – known standardized idling – short circuit method. The proposed method is practically free from the limitation of the length of cable samples. This allows you to control all finished cable products without cutting off samples for measurements. The measurement error does not exceed the limit set by the standards equal to 1 %. The results obtained provide non-destructive testing during acceptance tests of cable products intended for intrinsically safe systems.

Methods of increasing accuracy of measurement results of S-parameters of waveguide devices operating in the upper part of extremely high frequency range are reviewed. It is shown that accuracy and reliability of measurements of S-parameters of waveguide devices depend on the quality of contact between waveguide flanges: leakage of electromagnetic radiation through gaps poses a significant problem and can lead to unreliable results in measuring insertion loss and voltage standing wave ratio. Therefore, particular attention is paid to quality of contact between the measurement system and the device under test when operating in the millimeter wavelength range. In this paper, a contactless waveguide adapter flange for millimeter wavelength range insensitive to any air gap when connected to the device under test is designed. The waveguide adapter with contactless flange constitutes a section of a standard WR10 rectangular waveguide terminated on one side by a standard UG-387 flange and on the other side by the proposed contactless flange with a pin-like structure. Use of an adapter with a contactless flange allows for minimizing issues related to measuring insertion loss and return loss caused by incomplete contact or lack of it when connecting two waveguide flanges. This type of flange connection can be used for rapid measurements because no flange screw fastening is required. A comparative analysis of a standard adapter and an adapter with a contactless flange is performed in a WR10 waveguide channel. Efficiency of contactless coupling is experimentally confirmed within the entire operating range of 75 to 110 GHz with a 100 μm gap at the edge of the waveguide coupling. Use of a waveguide adapter with a contactless flange allows for faster and at the same time more accurate measurement of S-parameters of the devices under test. This adapter is indispensable for quick certification of millimeter-wave waveguide devices by modern metrological tools (vector network analyzer and scalar network analyzer).

Pure materials are in demand in many sectors of the national economy, including the metrological service. High purity organic material is the ultimate source of metrological traceability in organic analysis to the basic units of the International System of Units (SI). This article presents the general approaches to determining the mass fraction of the main component in pure organic chemicals, which provide a traceable connection between the certified value of substance purity and the basic SI units - mass (kilogram) and amount of substance (mole), the features of using direct and indirect measurement approaches are considered, specific analytical methods that can be used for this purpose are discussed. Determining the purity of an organic material in most cases is not a plain analytical and metrological task. Solving this issue requires the relevant instrumental methods and appropriate measurement procedure, which is able to provide a comprehensive study of organic matter and guarantee the necessary accuracy of the certified value. Taking in consideration the vast diversity of organic chemicals, the determination of the purity of organic substances will never be a standardized procedure.

A method for estimating the number of calibrations of measuring instruments used in production activities on the scale of the state economy is proposed and justified. The method is based on the calculation of the so–called calibration weight – the ratio of the annual turnover of the enterprise to the number of calibrations of measuring instruments performed at the enterprise. The number of calibrations of measuring instruments in the industry is calculated as the ratio of the annual turnover of the industry to the weight of calibration in the industry. Similarly, the number of calibrations is calculated for all sectors of the economy of the Russian Federation. As an example of the implementation of the method, the number of calibrations of measuring instruments in the Russian Federation in 2022 was estimated, which amounted to (96±34) million. The validation of the proposed method was carried out, which consisted in comparing the number of verifications of measuring instruments estimated using the proposed method with the number of verifications calculated based on data from FGIS Arshin. As a result, a match was obtained within the limits of the calculation error, which indicates the validity of the proposed method. It is established that the error is due to two main factors: the forced use of ultra-small samples with a volume of less than 10 when estimating the number of calibrations in groups of the All-Russian Classifier of Types of Economic Activity and the spread of values (variance) of the calibration weight in samples with a volume of more than 10. If we assume that the interval between calibrations is comparable to the verification interval, then according to the developed method for estimating the number of calibrations, the volume of the fleet of calibrated measuring instruments in the Russian Federation can be estimated approximately as 150 million units. Thus, for the first time in the Russian Federation, estimates of the number of annual calibrations, as well as the volume of the fleet of calibrated measuring instruments, were obtained. It is advisable to use the obtained results to assess the state of the country's measurement uniformity system, in the strategic planning of the development of the measurement uniformity system.