Pretreatment Of ECT Capacitance Signal And Characteristic Analysis Of Transformer Coupling Measurement Circuit

Electrical capacitance tomography(ECT)is a kind of process tomography technology,which can reflect the distribution of permittivity in the pipeline at different times according to the change of capacitance between sensors.ECT technology combines the data collected by the sensor with the corresponding image reconstruction algorithm to display the medium distribution map in the pipeline or container,and participates in the process control by extracting the characteristic parameters of the image.Due to the advantages of no interference to the original fluid flow,fast measurement speed,simple structure and wide application range,this technology has been widely used in the fields of electric power,chemical industry,energy,metallurgy,food and light industry in recent years.Electrical capacitance tomography data acquisition system is an important part of ECT system.On the one hand,optimizing the micro capacitance measurement circuit can avoid the influence of electrostatic interference and external electromagnetic field on the measurement signal as much as possible in the process of signal transmission.On the other hand,preprocessing the original signal and extracting the useful part of the signal can improve the accuracy of subsequent image reconstruction.Therefore,the research of capacitance measurement circuit and digital filtering method is of great significance.On the basis of previous studies,a transformer coupled capacitance measurement circuit is designed,and a composite filter combining median filter and LMS adaptive filter is proposed.Experiments and simulations are designed to verify the effect of transformer filtering,the performance of the whole circuit and the role of digital filter.The experimental and simulation results show that the transformer has anti-static and anti-interference performance,the composite filter can effectively reduce the impact of noise on the signal,and the hardware experimental platform can basically meet the data acquisition requirements of ECT system.