Research And Design Of Coating Thickness Gauge Based On Eddy Current Testing

Stealth technology is a key research area for defense technology.All countries in the world have invested a lot of financial resources and manpower to study stealth technology.Whether the stealth performance is excellent or not is extremely critical,it is the quality of the absorbing coating.The quality of the wave-absorbing coating is an important indicator of its accuracy and uniformity.In order to ensure that the stealth material has a high-precision thickness monitoring method in the production process,it is a key issue in the production process of stealth material.In order to solve this problem,it is necessary to periodically check the thickness of the material without damaging the material structure.After comparing several commonly used methods of industrial thickness measurement,this paper chose the eddy current method to measure the thickness of the absorbing coating.In this paper,the principle of traditional eddy current coating thickness testing,the equivalent model of pulsed eddy current nondestructive testing,and the application of lift-off effect in eddy current testing are combined.A method for measuring the thickness of the non-conductive coating on a non-magnetic metal substrate is proposed.Applying the theory,a design scheme for a handheld eddy current wave-absorbing coating detection instrument is proposed.The article first proposes the design scheme of the eddy current sensor.A highpermeability metal shield is used to restrict the magnetic field line of the eddy current probe to improve the detection performance,and the method of cutting-edge contacts is used to reduce the measurement error caused by the unevenness of the surface.Then an experimental platform was built to verify the feasibility of the sensor design scheme,and the experimental data was used to provide a reference for the circuit design.Then based on the MSP430 platform,the signal generation circuit,signal conditioning circuit,analogto-digital conversion module,power supply circuit and other modules were designed.Detailed parameter analysis calculation and simulation were carried out,and the noise analysis of the analog-to-digital conversion module was emphasized.Set up experiments to explore the degree of influence of circuit noise on the final result.The experimental results show that the ratio of circuit noise to the final detection result is less than 0.02.The article adds a temperature compensation module to the existing coating thickness measurement fitting algorithm.The experimental results show that temperature compensation can effectively improve the accuracy and stability of the measurement.With the designed prototype,the design experiment explores the factors that affect the measurement accuracy of the prototype.The final experimental results show that the handheld absorbing coating thickness gauge can achieve a coating thickness range of 100um-700 um,and has a good measurement effect on the non-magnetic metal matrix non-conductive coating.Under the characteristics of stability and wide use,the prototype quickly measures the test piece with a relative error of less than 15 um.