###### Abstract  
An investigation of artificial flaws in electromagnetic non-destructive evaluation using eddy-current frequency-response analysis is carried out in this study. A new approach incorporating innovative solution is proposed. The goal was to increase the resolution of gained signals in contrast to the conventional sweep-frequency method. The proposed procedure was tested on real material specimens where differential responses were gained from artificial electro-discharge machined flaws. Two plate specimens having EDM flaws of various dimensions were inspected. Eddy-current responses due to the material flaws were sensed and compared to a dataset that was obtained by numerical modelling. The presented unique results clearly show that the resolution of a fixed probe driven with sweep-frequency excitation signal can be increased when the appropriate probe instrumentation is used and the characteristics are further mathematically processed. non-destructive evaluation; eddy current testing; sweep frequency approach; artificial flaws; harmonic excitation +
Footnote †: journal: Applied  
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for nonconductive materials, coating conductivity, substrate conductivity, etc. According to [PERSON] et al., the goal of conductivity evaluation may be achieved by analogizing eddy current testing to the parameter measurement process using the apparent conductivity. In their study, the authors evaluate both coil impedance and plane wave impedance, and the approximation relationship between them. They found that all properties of the coated plate may be determined by comparing the experimental curve of the experimentally gained equivalent conductivity of coil impedance with the theoretical curves of normalized apparent conductivity of plane wave impedance [3; 4; 5]. According to [PERSON] et al., the variations due to lift-off in coil impedance measured with the coil positioned above a conductive plate with and without a thin metallic coating can be utilized for the simultaneous assessment of the thickness and conductivity of metallic coatings. The lift-off effect was eliminated using an impedance coordinate transformation approach. The impedance of the coil placed above the plate under test was normalized by the impedance of the coil placed above two reference plates. The suggested technique, which combines the least-squares method with the Levenberg-Marquardt (LM) algorithm, may be used to determine the parameters of a multilayer metallic coating with a thickness of tens of micrometers on a conductive plate [6; 7]. When characterizing the multi-layered structure, the signals of the to-be-characterized layer are 'extracted' from the composite signals. [PERSON] et al. proposed the method of separating the signals of different layers by frequency band and characterizing the layer of interest by using the correspondent signals. The study of the simulated signals and the differences of the signal series in the frequency series yielded a few distinguishing parameters. The thickness of the top and bottom layers may be measured using high-frequency and low-frequency signals, respectively. The air gap between two conductive layers does not affect the variations in the signal series in the frequency series. They stated that even without knowing the plate's conductivity, the maximum difference in resistance in the frequency series can be used to characterize the lower layer regardless of conductivity changes and air gaps [8; 9; 10]. The impedance signal is an integrand of the form function and generalized reflection function when using SFECT to evaluate each layer's thickness in a layered construction. [PERSON] et al. presented the variable--a derivative of impedance concerning log scaled angular frequency to assess two closely linked layers.