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A Method of Improving Signal-to-Noise Ratio of Pulsed Eddy Current Detection Signal

A pulsed eddy current and signal detection technology, applied in the direction of material magnetic variables, etc., can solve the problem of inappropriate pulsed eddy current signal processing, and achieve the effect of filtering various periodic and quasi-periodic interference

Inactive Publication Date: 2011-11-30
HUAZHONG UNIV OF SCI & TECH +1
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Problems solved by technology

However, the methods mentioned in the above patents are not suitable for the processing of pulsed eddy current signals

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  • A Method of Improving Signal-to-Noise Ratio of Pulsed Eddy Current Detection Signal
  • A Method of Improving Signal-to-Noise Ratio of Pulsed Eddy Current Detection Signal
  • A Method of Improving Signal-to-Noise Ratio of Pulsed Eddy Current Detection Signal

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Embodiment Construction

[0030] according to figure 1 In the steps shown, first place the pulsed eddy current sensor on the component under test to obtain a set of original signals x1, such as figure 2 shown. The measurement time interval is [0, t], where the value of t is between 100ms and 10s. For example, for an iron plate with a thickness of 20mm, the value of t may be 200ms to 400ms. Intercept the signal x in the two intervals of the time interval [t-2T, t-T] and [t-T, t] 2 , x 2 ',Such as image 3 As shown, where T ranges from 0.2%*t to 20%*t. For example, for an iron plate with a thickness of 20mm, a possible value of T is 5%*t. Then find x separately 2 and x 2 'The integral value of segment, denoted as c and c', let d=|c-c'|. Compare d with the preset threshold value d t compare, d t is a quantity related to the signal magnification, the hardware resolution of the data acquisition system and the noise intensity of the surrounding environment, d t The value of satisfies the followin...

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Abstract

The present invention proposes a method for improving the signal-to-noise ratio of the pulsed eddy current detection signal, by first intercepting a section of waveform in a certain time interval from the original signal, and judging whether this section of signal is a pure noise signal that does not carry specimen information , if yes, perform periodic extension on the quasi-periodic signal to obtain a signal with the same length as the original signal, subtract the original signal from the signal obtained by the periodic extension, and finally perform median filtering on the subtracted signal . By adopting this method, various space electromagnetic field interference signals and white noise in pulsed eddy current detection signals can be effectively filtered out, signal drift can be suppressed at the same time, and the anti-interference ability of the instrument system can be improved.

Description

technical field [0001] The invention belongs to the field of non-destructive testing of ferromagnetic materials, in particular to a method for improving the signal-to-noise ratio of pulsed eddy current testing signals. Background technique [0002] Pulsed eddy current testing technology is a new method different from conventional eddy current testing methods. It can break through the limitation of skin effect in traditional eddy current testing technology and detect deep-seated defects in metal materials. This method is to pass a pulsed current to the excitation coil close to the test piece. When the current disappears, an eddy current will be induced in the test piece, and the frequency component of the eddy current is closely related to its penetration depth. The excitation frequency is wide, which contains low-frequency components, so the eddy current induced in the specimen also contains corresponding low-frequency components with strong penetrating ability. The pulsed ...

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01N27/90
Inventor 武新军林树青黄琛沈功田徐江康宜华石坤
Owner HUAZHONG UNIV OF SCI & TECH
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