Development and Application of Pulse Eddy Current System for Testing Purity of Sandwich Gold Plate

Since there is no difference in appearance, overall density or surface composition between sandwich gold plate and pure gold plate, the purity of sandwich gold plate is difficult to test by existing non-destructive methods. A technical route for evaluating the purity of sandwich gold plate based on pulsed eddy current was proposed, and a pulsed eddy current system for testing the purity of sandwich gold plate was developed. It included the development of signal generation and acquisition dual function modules based on field-programmable gate array (FPGA), the selection of power amplification module considering load effect, the development of sensor based on self-developed winding machine, the development of signal amplification module with adjustable gain and DC bias, the development of 4-channel temperature control module, the development of hybrid power supply module including linear power supply and switching power supply, the development of control and data analysis software based on C++, Qt and Python, and the training and verification of deep learning model based on residual shrinkage network. Through the application test, it was found that the system could not only distinguish between pure gold plates and sandwich gold plates, but also classify the purity of sandwich gold plates according to the gold content of 99.990%, 99.900%, 99.000% and 95.818%, and the accuracy rate were not less than 90.08%.