Electrocardiograph: A Portable Bedside Monitor

Electrocardiograph is a biomedical device that measures electrical potential generated by electrical activity that occurs due to the heart's pumping action. The graphical presentation of the Electrocardiogram (ECG) can be interpreted so that normal and abnormal rhythms of the heart can be detected and diagnosed. Design, construction and manufacturing of this device in Africa would improve access to health care, create employment and improve the African economy. The major materials considered for the implementation include the instrumentation amplifier AD624, Low Noise JFET Operational Amplifier TL074, a clinical standard 12-lead ECG electrode, various electrical and electronic components such as resistors, capacitors and diodes for protection and an oscilloscope. The electrodes connected to the body convert the heart signal into electrical voltage. These voltages obtained from the body are too small for the oscilloscope to capture and so are amplified using AD624. Noise from the environment affects the ECG signal. To suppress the noise, the signal from the amplifier is filtered. According to the International Electrotechnical Commission (IEC) specification, the bandwidth required for an ECG filtering is between 0.5Hz – 150Hz. Band-pass filtering is used. The signal obtained from the band pass filter stage is then passed through a notch filter to further eliminate 50 Hz noise from the power line. The result is then displayed on an oscilloscope. The Electrocardiograph was tested on different subjects and the results compare favourably with results obtained with imported ECG monitor.