Development of a Single-Channel ECG-Circuit

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Supervisor:
Szombathy Csaba Zoltán
Department of Broadband Infocommunications and Electromagnetic Theory

ECG and pulse signals are important human physiological signals, where information of the human cardiovascular system can be deduced. Therefore the analysis of these signals is important for detection and prevention of cardiovascular diseases.

The single channel ECG signals and multi-channel ECG signals can be acquired, displayed and analyzed. Several medical personals use single channel ECGs due to their simplicity and selectiveness to perform automatic functioning and measurement. These systems can also be used for future study on the diseases related to the different structures and functions of bilateral vascular systems.

This Thesis paper discusses and explains the design and operation of a single channel analog front end of the ECG circuit, which has been built. The analog circuit contains an instrumentation amplifier design with a very active common mode signal rejection. A compensation control circuit has also been employed to cancel common mode voltages/Interference and a half supply voltage generation circuit is used to serve as a virtual ground for the circuit.

This ECG circuit can detect ECG pulses and is also capable of driving a digital display circuit.

In this architecture, analog blocks, e.g. high gain amplifiers, and passive elements, such as capacitors and resistors, have been used.

A 3 lead ECG system was used in this thesis. The voltage was obtained from a pair of chest electrodes, whereas the third electrode served for common mode voltage cancellation. The ECG waveform was finally displayed on a digital oscilloscope.

The paper further provides a theoretical section on Electrocardiography, ECG wave/signal properties, and a detailed description of 3-Lead ECG.

Key results: The ECG circuit was able to detect signals that were seen on the oscilloscope. The analysis also contained observing the characteristics of the detected ECG pulses.

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