Realization Of Bioelectrical Signal Acquisition Device Under Electromagnetic Stimulation

Surface electromyogram(s EMG)originates from the motor neurons in the spinal cord.It is a common bioelectrical signal and is the source of electrical signals that generate muscle force.It can be obtained through the guidance of surface electrodes.It contains a variety of information about muscle activity,and reflects neuromuscular function.Therefore,its detection and analysis are of great significance to neuromuscular diagnosis,sports medicine and other aspects.This thesis aims to study and design a set of surface electromyography signal acquisition devices with good anti-noise performance,and tests its reliability and effectiveness through experiments.Firstly,the production mechanism and mathematical model of the EMG signal were introduced,which found a theoretical background for the research and design of the subsequent acquisition device.Secondly,the characteristics of surface EMG signals were understood.The various noise interferences that may be faced in the acquisition process were fully considered.On this basis,the design of the acquisition device was determined.The device included the signal detection,pre-amplifier signal amplification,band-pass filter,power frequency notch,signal secondary amplifier and display terminal.The device designed in this thesis used a low-impedance differential electrode,which reduced the signal loss from the source and suppressed the common-mode interference.The amplification of the signal used the scheme of amplifying step by step,so that it reduced the performance requirements for chips,and saved costs.On the other hand,it also helped to prevent the direct current component from being excessively amplified before the signal was filtered,which avoided the weak electromyographic signals were submerged.It also facilitated flexible adjustment of gain amplification.In addition,the 10th-order Sallen-Key band-pass filters with speedy stop-band attenuation was used,it had a strong attenuation of environmental noise and other interference signals.The experimental results showed that the designed collection device had good anti-interference performance and the collection effect was significant.Finally,surface electromyography signal acquisition experiments were designed.Through the three experimental methods of physical movement,physiotherapy instrument stimulation and direct current stimulation to acquire the surface EMG signal.Based on the time domain analysis,the thesis used software to analyze the signal spectrum,and compared the results to verify the reliability and effectiveness of the design.