A High Impedance Front End Study Of Wearable ECG Detection

With the advancement of science and technology,the problem of population aging is becoming more serious,and the prevention and treatment of cardiovascular diseases cannot be delayed.The emergence of wearable medical devices has opened up new possibilities for this problem.Data acquisition sensing circuits are the primary components in wearable medical devices,and their performance and testing methods play an important role in wearable devices.Due to the weak and low frequency characteristics of human bioelectrical signals,the mainstream dry contact testing of wearable devices requires very high input impedance and low noise characteristics of the sensing circuit.In this paper,an ultra-high-impedance sensor amplifying circuit is proposed for the dry contact test of bioelectrical signals in wearable medical devices,and the noise model is established for the correlation analysis.The comparison between the simulation results and the theoretical results is given,and the comparison result proves the correctness of the noise model.Based on the analysis of the noise model,a related noise optimization method is proposed.Experiments show that the improved input impedance amplifier circuit can achieve input impedance up to 100GΩ or higher through the matching of peripheral components,and the equivalent input noise measurement result is only2μV.Based on the improved input impedance amplifier circuit,an ECG signal acquisition system with AD620 as the signal conditioning core was designed.The experiment was carried out by using the tin-plated electrode and the silicone electrocardiogram bandage to measure the human body ECG signal under dry contact.The ECG acquisition experiment shows that the impedance sensing front end can meet the application of dry contact measurement in the human ECG signal testing.