The Research Of Characteristic Of Metal Detector Based On Eddy Current

Eddy Current Sensor(ECS)is an nondestructive, non-contact testing component, which is extensively applied in engineering and science researches. The testing performances are sensitive to the material properties, which hampers eddy current sensor to more extensively apply. So it is important to study on the electromagnetic properties of ECS.This subject adopts finite element method combining with experiments to study the electromagnetic properties of ECS. The research works are follows:1. Theory study on the electromagnetic properties of ECSBased on basic operation principle of ECS, correlation parameter derives from theory analysis, sensor performances were influenced by correlation parameter, such as detection distance, frequency, etc.2. Study on the electromagnetic numerical simulation modelingBased on the modeling theory of FEM and the electromagnetic foundational theory, the finite element model is built by simplifying appropriately the original model, selecting the element type, meshing and defining the boundary conditions. Then, the model is solved, and established a set of numerical computation method of eddy current sensor.3. Finite element analysis of the electromagnetic properties of ECSThe effect of the tested material parameters (resistivity and magnetic permittivity), testing distance, coil size(internal and external diameter) and testing frequency and etc during testing. Based on the electromagnetic field simulation analysis of eddy current sensor of above factors, having influence on the performance of the eddy current sensor, The rule of the electromagnetic field of ECS and eddy field of tested are studied under esch factor.4. Study on the three dimensional entity model of multidetector ECS with ferrite core Establishing one calculating model for multidetector ECS with ferrite core three dimension electromagnetic field, doing theoretical analysis, drawing the contour map and vector graph of magnetic strength, analyzing eddy current density of distribution color graph with different angle of view by three dimension eddy field. So these results can intuitionistic show demagnetization effect and skin effect of cable core conductor. Under the different turns of coil, different size dimension of ferrite probe, tested radius and etc. Changing the value of eddy loss and stored energy were calculated, analyzing the relationship of these values, these can provide fundamental reference of ferrite eddy sensor.5. Emulation and design of eddy current sensorThis article designs experimental circuit of F/V to test the effects on the probe coil of eddy current sensor with paramagnetism and diamagnetism. Alarming circuit with sound and light can show to tested metal for distinguishing paramagnetism or diamagnetism.