Analysis of the uncertainty of measurement in pulsed eddy current signal evaluation

Lysenko, Iuliia; Nacional'nij tehnicnij universitet Ukraini Kiivs'kij politehnicnij institut imeni Igora Sikors'kogo; Ukraine

Kuts, Y.; National Technical University of Ukraine; Ukraine
Protasov, A.; National Technical University of Ukraine; Ukraine
Lysenko, I.; National Technical University of Ukraine; Ukraine
Dugin, O.; National Technical University of Ukraine; Ukraine

ID: ECNDT-0350-2018
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Session: Eddy Current-Techniques 3
Room: H2
Date: 2018-06-14
Time: 16:20 - 16:40

The probability of the pulsed eddy current NDT results depends on the measurement accuracy of the signal parameters of eddy current transducers. In particular, among such parameters are the frequency and attenuation ratio of harmonic oscillations, which arise in the pulse mode of the transducer. The process of evaluation of these parameters is accompanied by the emergence of a error random component, which is due to the noise effect of different nature, as well as the methodical component, which is determined by the features of the applied methods of digital signal processing and modes of obtaining experimental data. The standard uncertainty of measuring the frequency and attenuation ratio of the transducer signals obtained from signal’s amplitude and phase characteristics is analyzed in the article. The characteristics are determined by the discrete Hilbert transform of the transducer signals. The performed analysis and the obtained formulas can be used for engineering calculations of numerical values of measurement uncertainties of attenuation and internal oscillations frequency and recommendation justification for choosing the time length of observation intervals and signal analysis. The efficiency of the obtained results is confirmed by an example of the signal processing of the multi-differential eddy current transducer in the pulsed excitation mode for the crack detection tasks. The method of determination and analysis of transducer signals information parameters is given. The experimental results of the influence estimation of the electrical conductivity value of the sample material and the cracks depth on the informative parameters of the signal are given. The general character of the dependence of the attenuation and the frequency of the transducer signal oscillations from the crack depth in the testing object is established. The sensitivity of the transducer signal informative parameters to the change in the crack depth is determined.