Research On Key Technologies For Development Of Pulsed Eddy Current Testing Instrument

Pulsed eddy current testing(PECT)is a kind of detection technology that can acquire multi-level information of components and achieve rapid non-stop detection under large lift.It is one of the hot spots in the field of non-destructive testing in recent years.This dissertation studys on the key technologies for the development of pulsed eddy current testing instrument so that it can better meet the pulsed eddy current testing requirements.Firstly,the principle of pulsed eddy current testing,the characteristics of excitation signal and detection signal are analyzed in detail.For the characteristics of positive and negative square wave excitation signal of pulsed eddy current testing,the excitation source scheme of pulsed eddy current testing is designed by using direct digital synthesizer technology with high frequency resolution,continuous phase and arbitrary waveform output.At the same time,for the characteristics of the large dynamic range and weak and difficult to extract,the data acquisition scheme of pulsed eddy current testing is designed by using high resolution,high-precision Σ-Δ analog to digital converter.Secondly,the hardware circuit design of data acquisition based on AD7760 is completed,and it is combined with the excitation source hardware circuit to form the entire hardware system.On this basis,the development of system software is completed.Based on the symmetry characteristics of pulsed eddy current testing positive and negative square wave excitation signal,a method of storing compressed waveform data to reduce the phase truncation error is proposed.This method has the characteristics of high compression ratio,low signal spur,etc.Then a square wave edge address discrimination method is proposed,The method uses the internal trigger acquisition method to complete the development of control software for integrating the excitation source and data acquisition functions.Finally,the development of excitation source and data acquisition system of pulsed eddy current testing was completed,and the test and experimental platform was set up to test the system performance testing and system application.The results show that the system can generate positive and negative square wave excitation signals with continuously adjustable parameters,and the signal quality meets the excitation requirements.The data acquisition resolution is high and the pulsed eddy current detection signal can be obtained accurately.The system is able to generate high quality excitation signal,achieve accurate detection signal acquisition,meet design goals,and meet pulsed eddy current testing requirements.The pulsed eddy current testing excitation source and data acquisition system is a key component of the pulsed eddy current testing instrument.Its successful development can improve the instrument detection effect and accuracy,and better serve the industrial site detection.