Research On Measurement Method Of Metal Thickness And Conductivity Based On Single Coil Eddy Current

Thickness gauge is an indispensable measuring equipment in the process of plate and strip rolling.It can provide feedback information for the rolling mill control system to ensure that the product quality can meet the required thickness.Conductivity measurement can be used for the separation of plate materials.In view of the requirements of the industrial rolling field for the thickness of the produced plate,the non-contact thickness sensor and the measurement method currently used in practice have their own limitations.Therefore,in order to develop a fast and low-cost measurement method for rolling mill,this paper proposes to use single coil eddy current to measure the thickness and conductivity of plates with different characteristics.Based on the analysis of single coil eddy current detection principle and related technical methods,a single coil eddy current detection device is designed.The main work and conclusions are as follows:1.Based on the deep understanding of the development of eddy current testing technology at home and abroad,this paper studies and analyzes the theory of eddy current testing.In the process of studying the design method of single coil cylindrical probe,it analyzes the influence of the change of coil parameters on the magnetic induction intensity,and studies the equivalent circuit and coil impedance of eddy current testing,which provides the theory for the design of single coil sensor of eddy current testing on the basis.The finite element simulation model of single coil eddy current testing metal thickness is established by using Maxwell software in ANSYS.The influence of the parameter change of eddy current probe made up of single coil on metal thickness measurement is analyzed by finite element simulation.According to the difference signal of induction voltage and the sensitivity of thickness measurement,the reasonable coil parameters are selected as the principle of the final design of eddy current reasonable coil parameters are selected as the principle of the final design of eddy current testing coil probe on the basis.Then,the relationship between the thickness of sheet metal and the coil impedance,the relationship between the conductivity and the impedance phase angle are studied by using the finite element simulation analysis and the impedance analyzer respectively.The data are fitted by polynomials,and the coefficients of polynomials are optimized by using the descent simplex method.The error between the predicted thickness,the conductivity and the actual observation value is small.2.The whole hardware circuit of eddy current detection system is designed,and then the sinusoidal excitation signal generating module is designed with stm32f4 single chip microcomputer as the core,and the related signal processing module,amplitude and phase detection module,signal acquisition module and data processing module are built.3.Combined with the theoretical analysis and simulation results,the thickness and conductivity of different metal materials with different thickness are tested by the single coil eddy current testing platform,and the thickness and conductivity are measured by the coil impedance value and phase angle.The experimental results show that the thickness and conductivity of the plate can be measured by the polynomial fitted by the reduced simplex method.The error of thickness measurement is less than 5%,and the error of conductivity measurement is less than 0.4%.