Thickness Detection System Receiving And Processing Technology Of Metal Plate Based On Electromagnetic Ultrasonic

Aluminum plate is widely used in automotive, aerospace, petrochemical and other fields, accurate measurement of aluminum plate thickness is important guarantee to improve the quality of aluminum plate products in China. In engineering applications, ultrasonic thickness measurement of aluminum is one of the common means. Traditional piezoelectric ultrasonic detection due to its advantage of high sensitivity, high signal-to-noise ratio is widely used in the factory inspection, but in the measurement process to apply coupling agent, and unable to bear high temperature of the external environment of detection existing limitations. The electromagnetic ultrasonic measurement have the characteristics of non-contact、not needing to daub coupling agent、resisting to high temperature and high pressure being a good supplement.In this paper, the electromagnetic ultrasonic transducer and the principle of thickness was studied, and the electromagnetic ultrasonic transducer was deduced in the thickness of the application of mathematical formula. According to the electromagnetic ultrasonic transducer work in the condition of thickness of excitation principle and thickness of echo signal points, designing the part of the hardware of electromagnetic ultrasonic echo receiving module, and using Multisim simulation software of each part of the receiving module are simulated. In the aspect of experiment, using the electromagnetic ultrasonic thickness measurement platform test aluminum plate for the actual measurement. Base on the different thickness of aluminum plate conducting multiple sets of repetitive data acquisition experiments, and read the adjacent echoes peaks corresponding to the time difference to calculate the their thickness values. In the process of data processing, according to electromagnetic ultrasonic signal,s characteristics, using a variety of applicable to the category of data processing method for data processing, and make the comparison. Eventually determine the use of the moving average method and wavelet transform method. In the process of wavelet transform signal processing, "Clans" wavelet base first layer decomposition coefficient poor sequence to select the best wavelet base which is suitable for the signal. On the basis of choosing the optimum wavelet base, exploring the different decomposition scales for influence of the error range on the thickness value. After moving average method the processed data to reduce the range, but every data to have influence on the average data set that contains the data. Moving average of data from a data set, which the more its measuring accuracy is higher, but the real time response will be worse.Experimental research on the different thickness of aluminum plate, the results show that: raw signal data after the moving average processing method, although the accuracy is decreased, but the processed data values and the real value comparison data as a whole is too large; Raw signal data after wavelet transform processing, accuracy is improved, the range of error reduced volatility, choose a small Porgy and decomposition scale can effectively improve the electromagnetic ultrasonic thickness measurement accuracy.