An Active Electrode Based ECG Measurement System from Minimally Spaced Precordial Bipolar Lead
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Electronics miniaturization leads the development of small wearable Electrocardiography (ECG) devices. These devices are getting special attention due to current trends in Human-Computer-Interaction applications and remote patient monitoring. Therefore, user comfort is an essential requirement for these kinds of devices where the number of electrodes and the distance between the electrodes is kept short. This short inter-electrode-distance (IED) degrades the signal quality which leads to poor signal-to-noise ratio (SNR). In this thesis, a novel measurement system was developed to record ECG from bipolar chest lead with short IED. The measurement system was developed with single supply, low noise active electrode (AE) and ADS1299 Evaluation board (EVM) to evaluate the performance of active electrode with ADS1299 ECG analogue-front-end (AFE). The low noise, high input impedance, and precision components were given priority during the design of the AE. The performance of the developed system was carried out by testing common mode rejection ratio (CMRR), SNR and frequency response. The system was used to record ECG signal with commercial product BN-RSPEC module with different IED in diagonal orientation near the heart’s main axis. The single supply AE+ADS1299 system demonstrated excellent noise performance over the specified bandwidth of 262 Hz. The system also demonstrated high CMRR at 50 Hz. The most noteworthy accomplishment of this thesis was that the developed system is capable of recording P wave from the midsternum with a short IED of 0.3 cm. Although the measurements were performed on a single subject, this system outperforms the BN-RSPEC module from BIOPAC Inc. in recording from the close spaced electrodes.