Vol 58, No 10 (2016)

The composition and metrological characteristics of the National primary standard GET 210–2014 for the units of specific absorption of gases, specific surface, specific volume, and pore size of solid substances and materials are examined.

A method for evaluating the accuracy characteristics of the apparatus for recording and playback of signals from global navigation satellite systems is examined. This method is based on determining the distortions in the delay of the signal from different spaceborne navigation systems.

A mathematical method is proposed for predicting the state of a dynamic system based on arriving measurement data. This method is based on early detection of the hidden evolution of the system and its transition to an extreme state by evaluating the stability and catastrophic states of the system with each new measurement. The method is illustrated by an example of predicting an earthquake in Kamchatka and the period during which it is hazardous.

Analytic relationships for the errors in measurements of the frequency of a harmonic signal of limited length against a noise background with the use of the weighted method of frequency averaging are presented. Two parameters that provide an objective description of the properties of weighting functions in problems involved in the measurement of the frequency of a signal against a noise background are proposed. Optimality criteria of the weighting functions are formulated and a method of minimization of the measurement error is proposed.

A strain measuring station for the dynamic testing of dampers is described. The mechanical stresses are measured using strain-resistive sensors, connected in a measuring Wheatstone bridge circuit. A justification for the choice of the electronic components is presented and practical recommendations are made for the development of similar devices.

An expression is obtained for the spectral characteristic of a signal that is optimal from the point of view of measurements of the delay and resolution of correlated signals. The optimum frequency characteristic of the filter, which enables the response of the output signal to be compressed compared with the width of its autocorrelation function, is synthesized. The frequency and time characteristics of the signals as a function of the compression filter parameters are investigated by mathematical modeling methods. It is shown that signals in the form of exponential functions have the best properties, which enable the error when measuring the time parameters to be reduced.

An improved speech recognition algorithm has been developed with additional signal processing units to increase the number of comparative data parameters and to reduce the natural and spectral distortion of speech signals. Using a verified database an experimental study of the algorithm was conducted.

A principle for the design of a geometry tool that is effective in diagnostics of small-diameter pipelines is developed. The use of a fiber-optic sensor which is sensitive to deflection and is based on multimode optical fibers or on fiber-optic Bragg gratings is proposed. The performance of experimental prototypes of the device is analyzed.

A procedure is proposed for separating atomic fountain noise, depending on atom flux density. It is assumed that atomic fountain frequency is affected by photodetector noise, fountain shot noise, spin-exchange noise, and probing signal noise. Taking account of these noise sources allows the accuracy of frequency measurements made using an atomic fountain to be improved.

Metrological problems associated with the measurement of dynamic load vector parameters in systems with three single-component vibration sensors are examined. Sources of dynamic error and false precession of the obtained vector are analyzed while using analog and digital measurement systems. A package of tasks has been developed to correct amplitude and phase distortions while measuring vector parameters of nonsteady-state dynamic loads.

A method of measuring the temperature of the internal medium of an organism by modulating the optical radiation in the sensitive element of a fiber-optical sensor as part of a precision medical thermometer is considered.

The features of measurements of the parameters of low-frequency noise with a spectrum of the form 1/f^γ of electronic components are considered. Expressions for the systematic error in determining the exponent γ from the results of single measurements of the spectral power density of the noise by a direct estimate at two frequencies, taking thermal and shot noise of the monitored article into account, are obtained and analyzed. Recommendations on minimizing the total error in determining γ are given.

It is shown that tone-pulsed, linearly frequency modulated, and noise signals supplement each other harmonically, so that it is important to use them in all levels of a verification scheme. Data from measurement experiments confirm the feasibility of this calibration procedure for acoustic noise emission by the sliding complex weighted average technique.