Bohdan Halyna
@kpi.ua
Department of Automation and Non-Destructive Testing Systems
RESEARCH, TEACHING, or OTHER INTERESTS
Engineering
Scopus Publications
Scopus Publications
Oleksandr Povcshenko, Viktor Bazhenov, Olha Pazdrii, and Halyna Bohdan
Private Company Technology Center
An electrostatic field mill (EFM) is widely used to measure the strength of electrostatic fields, the main drawback of which is the occurrence of large measurement errors (up to 15 % in the range from 0 to 1 kV/m). This paper examines the aspects of using transimpedance amplifiers (TIAs) for the tasks of converting the current received from the EFM sensor into voltage, which will make it possible to reduce the instrumental error and ensure the linearity of the atmospheric electrostatic field strength measurement. In the general case, for the functional circuits of the electrostatic field mill, which include a differential transimpedance amplifier, there is the use of two TIA circuits, which are connected in parallel. Despite the simplicity of implementation, such a configuration contains a number of disadvantages and is not optimal. In the paper, a comparative analysis of a typical circuit of a differential TIA and a circuit of an ungrounded differential transimpedance amplifier with zero voltage drop proposed by the authors is carried out. As a result of the analysis, it was established that the designed authentic circuit of the ungrounded differential transimpedance amplifier with zero voltage drop has better parameters of linearity and interference resistance, in contrast to the generally accepted one. The value of the signal-to-noise ratio for the proposed scheme improved by 42 % on average compared to the typical one. The main difference of the proposed scheme is that the stability of the amplification factor is ensured, the influence of the bias parameters of the operational amplifier is leveled, and the overall noise level is reduced. The use of the designed scheme of an ungrounded differential transimpedance amplifier with zero voltage drop could make it possible to increase the accuracy of the measurement of the electrostatic field strength
H. Bohdan, V. Bazhenov, and A. Protasov
IEEE
At present, an acoustic method of testing is used for inspection products of aviation equipment made of powdered structural materials. One of the main information parameters is the velocity of acoustic wave propagation. The reliability of the testing essentially depends on the accuracy of measuring the transmission time of the acoustic wave in the material, in other words, on the accuracy of measuring the phase shift between the emitted and reflected signal. To increase the accuracy of this parameter, it is proposed to use a discrete orthogonal method. The results of applying the proposed method for measuring the phase shift between two signals for different signal-to-noise ratios for different values of the phase shift are presented in the article. Comparison of the results obtained experimentally and by simulation is given. Simulation was performed in the Matlab system, where virtual signals were created with a given noise level. For experimental verification of the method, a two-channel generator was used, which made it possible to generate signals with the necessary phase shift and the signal-to-noise ratio. The paper proposes a scheme for measuring the phase shift of signals, which implements the discrete orthogonal method and has high noise immunity. The obtained data confirm the effectiveness of the proposed method, which makes it possible to provide an error in measuring the phase shift of harmonic signals of less than 1 ° with a signal-to-noise ratio equal to 10, and this accordingly provides an error in measuring the time interval of less than 1%. The article also describes the practical implementation of the proposed system for measuring the time interval between two radio pulses at a frequency of 5 MHz. As a testing object, a composite material of the LaB6-TiB2 type was used in the shape of a rectangular prism with a side dimension of 3 mm.