Research On The Method Of Measuring Metal Conductivity And Thickness Based On Pulsed Eddy Current

With the rapid development of industrial automation technology,the application of sheet metal in the industrial field is more and more widespread.As a result,the requirements for the thickness of sheet metal and the selection of materials in the field of industrial rolling have become more and more important,and the requirements for metal measurement accuracy have been improved.The thickness and conductivity of metal plates are two important technical indicators that measure the quality of metals and the properties of metal materials.They can be used to sort metal materials and determine the state of metals.However,there is no complete set of equipment on the industrial site to measure the thickness and conductivity of the metal sheet at the same time,and the jitter generated during the rolling of the sheet will have a serious impact on the measurement accuracy.Therefore,a set of plates can be measured simultaneously.Thickness and conductivity can eliminate the influence of jitter on the measurement accuracy of the measurement device,making it possible to monitor and adjust the technical parameters of the plate thickness and conductivity in real-time so that the accuracy of the thickness and conductivity to meet the needs of the site is particularly important.In this paper,by consulting a large amount of literature,comparing and analyzing the advantages and disadvantages of measuring the thickness and conductivity of sheet metal,choosing the pulse eddy current technology to introduce its development and advantages,researching the research status of pulse eddy current technology at home and abroad,and providing the subject Theoretical basis.A finite element theory model was established to simulate the analysis of different metal conductivity measurement methods.A non-contact pulsed eddy current measurement device based on ARM is designed to effectively eliminate the lift-off effect and accurately calculate the thickness and conductivity of the metal plate.The main research content includes:(1)A basic introduction to the traditional method of measuring the thickness and conductivity of metal plates is provided.The common methods of thickness include manual measurement,mechanical contact measurement,ray measurement,ultrasonic measurement,eddy current measurement,and pulsed eddy current measurement.Common methods for conductivity include direct current four-probe methods,eddy current methods.The advantages and disadvantages of several methods were compared and analyzed.Finally,pulse eddy current measurement technology was selected for measurement.(2)Introduced the basic theory of Maxwell basic equations,electromagnetic field,eddy current field and some other eddy current measurement methods.Maxwell simulation software was used to analyze the eddy currents in four different conditions of lift-off,different currents,different frequencies and different number of turns.Plate penetration depth effect.The relationship between the electrical conductivity and the phase angle was calculated for different materials and thicknesses.The phase angle data was obtained by measuring the actual object with an impedance analyzer.The electrical conductivity of the actual plate was calculated and compared with the simulation data.(3)Based on the hardware circuit design of ARM non-contact dual coil pulse eddy current measurement device,the overall design of the measurement device and six modules of the hardware circuit including pulse signal,MOSFET drive,dual coil sensor,signal detection,AD The structure and function of the processing and communication circuits allow the hardware circuits to work properly through software programming.The software that the system runs includes three parts:lower computer,signal processing,upper computer.The lower unit is composed of pulse signal generation,AD sampling,etc.;the signal processing part uses median filtering,FIR low-pass filtering and wavelet filtering to compare the results of denoising;the upper computer uses C#to write the entire interface.Serial communication makes data,measurement results,and images can be measured and monitored online in real time.The entire system solves the effect of lift off effects on measurement accuracy caused by traditional single coil measurements.(4)Selecting a polynomial fitting method and BP neural network method to measure metal thickness and conductivity.The experimental results show that the measurement accuracy based on BP neural network method is higher than the polynomial fitting method.The thickness measurement error is 0.5%,and the conductivity measurement error is 3%,in line with industry standards.