Research Of Measuring Coating Thickness Method Using Hall Effect Sensor

In the modern industrial application,the coating has a wide range of applications,and the coating type is also developing towards diversification The thickness of coating not only affects the performance of workpiece,but also has great influence on the durability of the workpiece,so the research of coating thickness is given more and more expectation and task.However,the existing coating thickness measurement method is relatively single,especially nondestructive testing methods.There are only two method which take into account the convenience and accuracy:the magnetic resistance method and the eddy current method.This article aims to measure the thickness of non-magnetic coatings on different substrates.For the purpose of non-destructive testing,and to facilitate the use and realization of micron-level accuracy measurement,two solutions are proposed.Both methods use Hall Effect senor to gauge magnetic field to measure the thickness of the coating indirectly.The two methods are respectively applicable to the non-magnetic coating on the surface of the magnetic substrate and the non-magnetic coating on the non-magnetic substrate.In particular,the measurement of the non-magnetic coating on the surface of the magnetic substrate is achieved by measuring magnetic field near the magnetic substrate when the permanent magnet magnetizes the magnetic substrate at a certain distance.The measurement of the non-magnetic coating on the surface of the non-magnetic substrate is achieved by measuring the magnetic field of the alternating coil by the eddy currents induced by the non-magnetic substrate.In this paper,theoretical analysis and modeling simulation methods are used to demonstrate the feasibility of the two methods.Accordingly,the two different types of probes were designed,including structure and key parameters of the probes.Meanwhile,this paper has also developed a set of measurement system that is suitable for the Permanent Magnet Coating Thickness Measurement method.In this paper,the hardware and software design of the system are described in detail,and the experiment is performed by using the system.The relationship between the magnetic induction intensity and the thickness of the coating on the surface of the substrate is obtained experimentally.The idea of using eddy current thickness measurement failed to achieve the desired effect,This article makes a detailed analysis of the experimental results and their causes,and proposes a new direction for follow-up research.