Study On Aluminum Foil Thickness Test System Based On DSP Controlled On Line

Eddy-current sensor test technology is a kind of very popular untouched nondestructive test technology developed in last decades, which makes up five major modern nondestructive test technologies together with magnetic particle test, radial test, ultrasonic test and osmosis test. The nowadays of eddy-current test technology, the application field of eddy-current test technology and the development direction of eddy-current test technology are present in this paper.Understanding the basic theory of eddy-current test is the basis of selecting eddy-current test plan. In chapter 2, eddy-current test theory is analyzed from several aspects. Though analyzed the equivalent circuit of eddy-current test, the reliability of eddy-current test technology on aluminum foil thickness test on line is given and the eddy-current sensor design method and the eddy-current sensor parameters selecting are discussed.Hardware design is the basis of the whole system and the other system designs must be made on the basis of it. Together with the facts in chapter 3, the hardware microprocessor system that made by DSP chip of TI corporation is used to process the sample signal. Hardware circuit design is divided three parts. Generated frequency circuit includes frequency divided circuit and frequency composed circuit to generate stable frequency signal to sure the test task. Eddy-current sensor conversion circuit consist amplification circuit, band-pass filter circuit, demodulation circuit, differentiation phase and data sampling circuit. These circuits are used to convert the test signal of eddy-current sensor to discrete signal tend to process. The microprocessor system that formed of DSP chip is used to data fitting of test system, data displaying and data communicating with personal computer, etc. The interference questions of hardware design and the measure ofeliminating interference signal in the subject are introduced in the last of this chapter.After the hardware circuit of test system is conformed, the function of test system is relayed on the software. The software design ideas of the subject, system automatic test during the design, system consistent error disposal and software anti-interference questions are recommended in chapter 4.There have not avoided test errors in the test process. Except the hardware measures are taken to eliminate the errors, the methods of eliminating errors from data fitting aspect are introduced in detail in chapter 5, that is immune algorithm. The results have testified to get higher precision using immune algorithm to process sampling data compare with using B-P algorithm. Though analyzed the whole error of the test system, the results proved feasibility of the design plan of test system.