Vol 62, No 7 (2019)

The composition of the State Primary Standard of the unit of absorbed dose and unit of absorbed dose rate of beta radiation in tissue-equivalent material, GET 9-2018, is described and the metrological characteristics of GET 9-2018 are presented. It is shown that that the metrological characteristics of GET 9-2018 conform to modern domestic and international requirements regarding precision and range of reproduction and transmission of the unit of absorbed dose and unit of absorbed dose rate of beta radiation and its transmission to working standards and means of measurement. The technical characteristics and physical principle of operation of an automated extrapolation ionization chamber produced from the components of GET 9-2018 are considered.

A description of the State Special Primary Standard of the unit of absorbed dose rate of intense photon, electron, and beta radiation for radiation technologies GET 209–2014 is presented. The composition and technical and metrological characteristics of GET 209–2014 along with methods of reproduction and transmission of the unit of absorbed dose rate of intense photon, electron, and beta radiation are described. GET 209–2014 supports high-precision measurements of the absorbed dose of ionizing radiation during radiation-based technological processes in the treatment of food products and agricultural raw materials.

The technology of obtaining reference samples of volatile organic compounds using sorption microsystems is described. The most effective are 0.147–0.178 mm (80–100 mesh) polymer sorbents fractions, which provide high sorption properties, optimal gas-dynamic characteristics and minimal dead volumes. Stability of the reference samples during storage for 0.5 to 1 year is investigated. On the example of chamomile (Chamomilla recutita (L.)) growing in Samara region (Russia), it is shown that sorption microsystems can be used to identify complex objects and authenticate plant raw materials.

The problem of monitoring the accuracy characteristics of an automatic system for determining the astronomical azimuth is solved. The importance of this problem arises from the lack of a high precision standard with which the characteristics of this system could be monitored by comparison. An approach is developed for estimating the increments (changes) in the values of the astronomical azimuth on the sighting axis, as well as of the control element for an automatic system for determining the astronomical azimuth for specified forced changes in its intermediate parameters. The estimated accuracy of the system is substantiated theoretically. Special algorithms for fi nding the expected increments in the values of the astronomical azimuth are examined. Some practical ways of using this approach are proposed.

A procedure (algorithms and programs) for the construction of reference cylinders is proposed: the largest inscribed cylinder, the smallest circumscribed cylinder, and the boundary cylinders for the minimum zone. The parameters of the cylinders, i.e., the radius and position of the axis of the cylindrical surface in space, are determined by minimizing or maximizing a corresponding functional constructed on the basis of the coordinates of the points on the surface. The programs are implemented in the Mathcad program package and are applicable under laboratory conditions in experimental studies, as well as for developing program support for means of measurement. The proposed algorithms can be used to determine deviations from cylindricity of surfaces of parts in machines and devices.

The problem of developing measuring instruments for high levels of laser power of the pass-through type was posed and solved. Methods for solving the problem are presented. A measuring instrument has been developed, in which a two-step circuit design is applied for power attenuation of the laser beam to an operating level as measured by the radiation detector. It is shown that due to the original design of the attenuation steps and their arrangement in relation to the laser beam it is possible to achieve values of the attenuation coefficient of (0.2–0.4)·10¹⁰ and to measure power up to 10–15 kW without forced cooling of elements of the measuring instrument. Application of the design of steps makes it possible to reduce the dimensions of the measuring instrument and pass practically all radiation to the output without changing the characteristics of the initial laser beam. The measuring instrument that was developed differs from known analogs and is suitable for work with process lasers. For reliable measurement of laser radiation power, the conditions were determined for selecting the time constant of integration of the radiation detector. The connection between the time constant of integration of the radiation detector and the geometrical characteristics of the measuring instrument is shown.

Based on the Hilbert transform, measurement errors of the amplitude and frequency of a vibrating signal of variable frequency are studied. The chief factors affecting measurement error of the parameters of a signal were determined by means of numerical modeling. The use of a frequency response model of a vibration isolator in the form of a Chebyshev digital filter confirmed the effectiveness of the Hilbert transform. The results of numerical modeling were successfully verified during field tests of the vibration isolator at an electrodynamic workstation.

Multifrequency eddy current measurements of the thickness of non-magnetic metallic materials with dielectric coatings have been carried out. Based on the principal component analysis, the influence of competing factors such as electrical conductivity, thickness of the metal substrate and thickness of the dielectric layer is separated. Using the projection method on latent structures, eddy current measurements have determined the numerical values of the thicknesses of aluminum and copper plates and dielectric coatings.

A digital method is proposed for determining the initial phase of a harmonic signal at a sampling frequency less than the Nyquist frequency. The method includes sampling and quantizing the original signal using two analog-to-digital converters. The converters operate at two different frequencies less than the Nyquist frequency. The digital method for determining the initial phase of the harmonic signal is implemented in software in the MATLAB environment and in hardware on the Xilinx ZYNQ-7000 SoC platform. This method allows one to determine the initial phase of the harmonic signal from samples made at a frequency less than ten times the Nyquist frequency.

We describe the method of aspiration capacitor intended for the complex verification and calibration of highly sensitive equipment aimed at the measuring the specific electric conductivity of air (up to several fS/m) and used in the course of sounding of the bottom layer of the atmosphere and air in sealed compartments and clean rooms. We present a description of the engineering tools used for testing, verification, and calibration of these measuring instruments. We also present a structural scheme and describe the principle of operation of a high-stable generator of specific electric conductivity of air developed at VNIIFTRI. Finally, we give the results of measurements of the specific electric conductivity of air performed with the help of the described measuring instruments and show that the relative error of measurements does not exceed 2.5% for a normalizing value of 40 fS/m. This enables one to perform the verification and calibration of the existing types of measuring instruments.

We present the results of comparison of national standards of the units of sound oscillation velocity of water particles within the range from 5 Hz to 10 kHz performed by the Hangzhou Applied Acoustics Research Institute (Pilot Laboratory) and the All-Russia Research Institute of Physicotechnical and Radio Measurements (VNIIFTRI) (COOMET 646/RU/14 Pilot Comparisons). The calibration capabilities of the participants were evaluated according to the results of measurements of the sensitivity of oscillation-velocity receivers: KGP-10, VHS56, and VHS90. At frequencies varying from 5 Hz to 500 Hz, inclusively, the calibrations were performed in a chamber as a result of comparison with a reference hydrophone performed by the method of oscillating water column. At frequencies higher than 500 Hz, we used the measuring procedure of the reciprocity method in the free field of traveling spherical sound waves. No significant inconsistencies in the calibration results were discovered at any frequency used for comparisons. The maximal discrepancies between the values of sensitivity obtained by the participants did not exceed 1.2 dB.