Research On Echo Signal Processing Method And Its Application In Remote Industrial Density Meter

At present,with the rapid development of China's chemical industry technology and the increasing demand for intelligent chemical production lines,the corresponding on-line industrial intelligent instruments emerge as the times require.In the working process of the remote ultrasonic density measuring instrument,because the acquisition accuracy of the echo signal is low,and the collected signal contains a lot of interference noise,the measurement accuracy is not ideal.In order to improve the measurement accuracy of the ultrasonic densitometer,this paper optimizes the ultrasonic echo acquisition module.It improves the echo signal processing method to improve the signal-to-noise ratio of the ultrasonic echo signal and the measurement results.On the other hand,most of the existing ultrasonic density measuring instruments still need to be operated on-site,and there are few kinds of instruments compatible with the original production equipment.In order to solve this problem,the HART protocol is used as the solution to the communication part of the remote industrial densitometer.It not only solves the problem that only a single signal can be transmitted in the traditional 4-20 mA current loop but also takes into account the compatibility of the 4-20 mA current loop in the original distributed control system(DCS).Finally,the related software and hardware design are completed,and a set of high-precision remote industrial ultrasonic is developed;The wave density meter is suitable for most chemical production enterprises in China.The work content of the paper is mainly reflected in the following aspects:(1)According to the analysis of the echo signal propagation characteristics and sampling requirements of the ultrasonic density meter during the measurement process,an echo signal acquisition module based on the principle of random equivalent sampling is designed.Moreover by shortening the transmission time interval of the step pulse,the random equivalent sampling accuracy is improved,so that the high-frequency echo signal is converted into a low-frequency signal that can be collected,and the acquisition and reconstruction of the ultrasonic echo signal are completed.(2)For all kinds of noise interference in ultrasonic echo signals,this topic proposes a singular value decomposition denoising method based on generalized S transform.The generalized S-transformation is performed on the acquired ultrasonic echo signals to obtain a two-dimensional time-frequency coefficient matrix,and then the matrix is singular value decomposition,and the reconstruction matrix is determined according to the correlation coefficient between the decomposed component signal and the original transmission signal And the reconstruction of the order of,and finally inversely transform the reconstructed time-frequency coefficient matrix S into an echo signal sequence,so as to achieve effective denoising of the ultrasonic echo signal.Simulation experiments are carried out through the MATLAB platform to verify the effectiveness of the proposed algorithm.(3)Design and complete a remote industrial ultrasonic density meter.The STM32 microprocessor based on ARM7 is adopted as the core processing controller of the entire system,and the modular programming is carried out in the KEIL5 software environment using C language.Using the A5191 chip based on HART protocol,AD5421 conversion chip and related peripheral circuits to realize the remote communication function of the density meter,the instrument data can be stably transmitted in the current 4~20mA current loop.According to user needs,the corresponding PC software is developed under Lab Windows/CVI software to realize remote parameter query,setting and operation data monitoring and other functions.Experiments and field tests show that the measurement accuracy of the developed remote industrial density meter can reach 2.21% F.S.Compared with the existing conventional denoising methods,the proposed singular value decomposition denoising method based on generalized S transform can better preserve the singularity characteristics of the echo signal and improve the signal-to-noise ratio of the signal.Combine the echo signal envelope.The improved accuracy of the industrial density meter has been significantly improved and has been applied to actual production.