In this study, the discrete wavelet transform (DWT)-based signal processing methodology is applied for eliminating noise due to permeability variations in saturation eddy current (EC) testing signals from nickel tubes. The nickel tubes are of 0.3mmthickness and 6.6mmouter diameter. Systematic studies have been carried out to optimize the wavelet functions, number of decomposition levels, and thresholding algorithm for DWT processing based on the signal-to-noise ratio (SNR). The DWT processing has enabled reliable detection of a 0.1mmdeep notch located on the inner surface of the tubes meeting its stringent quality requirements. Application of signal processing-based methodology has resulted in an improvement in SNR of 11.4 dB as against 5.1 dB for the raw signals.
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