Vol 62, No 6 (2019)

The results of the development of methods for the transfer of units of water content in solid and liquid substances and materials are presented. Four types of comparison standards have been created for the transfer of units of water content, reproduced at the State Primary Standard of units of mass fraction, mass (molar) concentration of water in solid and liquid substances and GET 173–2017 materials. The procedures for the preparation of reference standards materials based on a mixture of organic solvents that are stable in water content and sodium molybdate dihydrate, which has chemically bound (crystallized) water, are described. The methods of reproducing the units of water content used in determining the characteristics of reference standards are presented: coulometric and volumetric Karl Fischer titration, air-heat drying and thermogravimetric analysis with mass spectrometric detection. The characteristics and standard uncertainties of the comparison standards, due to the characterization method, heterogeneity, long-term and short-term instabilities, are evaluated. The main changes adopted within the framework of the processing of the State verification scheme for means of measuring the water content in solid and liquid substances and materials are described.

We consider problems estimating measurement uncertainty for shape deviations in planar surfaces of large parts using the reference plane method. The sources of uncertainty in the implementation of various measurement schemes by this method are analyzed. The schemes are determined by the methods of realization of the output base – the plane defined by the three reference points of the supporting platform of the measuring system, as well as the methods of obtaining and processing primary measurement information. The results of experimental studies of the accuracy of a multisensor system designed to assess the topography of the flat surfaces of mechanical elements of particle accelerators are presented.

The deformation method of determining the metrological characteristics of variable-force measuring instruments is proposed and examined. The method consists in the excitation of variable forces by a piezoactuator and measurement of the proportional deformation of the elastic calibrated element by a laser interferometer. Unit transfer is shown from the State Primary Standard of units of length, velocity, and acceleration during oscillating motion of a rigid body under GET 58-2018, and the State Primary Standard of force, GET 32-2011. The uncertainty budgets of the determination of metrological characteristics by the known load mass method and the proposed method were compared. A schematic of a measuring installation implementing the proposed method is shown.

We consider the problem of measuring of the resonance frequency according to the amplitude-frequency characteristic of a resonator with the help of the method of stochastic approximation (SA). Various modifi cations of SA algorithms in the MATLAB software are investigated for a computer model of resonator with given parameters. The influence of the parameters of SA algorithms, noise, and the Q-factor of the resonator on the accuracy of measurements and the rate of convergence is analyzed. We also perform the comparative analysis of the indicated modifications of the algorithms.

Implementations of the variational method in transformer bridges with inductively coupled arms and in logometric bridges based on an operational amplifier with high amplification factor are described. It is shown that through the use of the variational method in transformer bridges it is possible to eliminate the influence of the basic error sources – impedances in connecting cables and transformer windings – and, in logometric bridges, by means of this method, eliminate the effect of the finite amplification factor of the operational amplifier and its input impedance on the measurement results. Theoretical and experimental investigations have shown that the measurement error may be reduced 100- and 1000-fold through the use of the variational method. Metrological data from impedance meters developed with the use of variational methods are presented.

The diversity of measuring tasks gives rise to a number of algorithms for data processing. The algorithms are included in the software of modern measuring instruments and make their own contribution to the resulting measurement error. A method is proposed for synthesis of algorithms for estimation of the dynamic error, the use of which makes it possible to eliminate computational difficulties that are characteristic for the traditional approach. This method is based on the methodology of the combined maximum principle. Analysis of the results of mathematical modeling in the problem of estimating dynamic error of the algorithms for data processing of measuring instruments confirms the effectiveness of using the proposed algorithm for estimating dynamic error of the software of measuring systems.

The aeroelastic instability of an ice-covered wire of overhead power transmission lines was investigated. An engineering method for calculating critical wind velocities is proposed. This method makes it possible to define the boundaries of the region of wire galloping of the split phase of a multi-span transmission line. The results that were contained can be used when developing measures to protect overhead power transmission lines from wire galloping.

Optical sensors of linear displacements with diffraction gratings serving as the measurement scales are investigated. A method of stabilization of the phase difference of quadrature measurement signals, consisting in the use of an analyzing scale with a special structure, is proposed. A design of an optical encoder based on the method is proposed. Mathematical simulation of the phase shift of the measurement signals as a function of the parameters of the diffraction grating is performed, and the results of the simulation are presented. The RCWA method is used to simulate the passage of radiation through the optical system. The optimal parameters of the structure of the analyzing scale are calculated. Experimental investigations of a mock-up of the encoder are performed and results of measurements of the phase difference of the measurement signals are presented.

We analyze flow and non-flow methods for verification of vortex flow meters and describe the basic advantages and deficiencies of methods in these two broad classes. We propose an enhancement to non-flow verification of flow meters that involves simulating and recording the effect of the material flow being measured on the sensor device, and describe an experimental test bench for improved flow meter verification in which the sensor element is exposed to direct electromagnetic excitation so that it vibrates at a specified controllable frequency. The tests were performed using a Yokogawa flow meter on the experimental test bench. The results obtained confirmed that the enhanced method for verification of the vortex flow meter is feasible for practical applications.

Temperature dependences of the isobaric heat capacity of stable and supercooled liquid carbon, which were obtained by processing thermograms of spontaneous cooling of spherical samples (levitation experiment), were determined. Using the thermodynamic analogy of the properties of the elements of the carbon subgroup of the Periodic Table for carbon, surface tension at the crystal–liquid interface, the size and the work of formation of the critical nucleus of the solid phase in a supercooled liquid, and the heat of fusion were found.

We propose a new original method aimed at the improvement of the frequency resolution of microwave hyperspectrometers in the SHF range for a given duration of single measurement and sensitivity. The method is based on the combined application of the multireceiver concept and the zero-measurement method. The block diagram is developed and the principle of functioning of the receiving channel of an SHF hyperspectrometer is described.

The variational method of increasing the precision of instruments for the measurement of the impedance parameters is considered. The method is based on variations of the coefficients of influence of the sources of an error on the result of measurements. It is shown that each variation of an influence coefficient of a particular source of error is accompanied by a corresponding measurement of the input quantity. A solution of the system of equations that describes these measurements and that makes it possible to obtain an exact result is presented. Devices used for different purposes constructed on the basis of the variational method are described.