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How to build your own heart monitoring device, a simple ECG

How to build your own heart monitoring device, a simple ECG

I have not been writing for some time and I am sorry for it. During the summer I got a three week scholarship in Germany. I had a great time there, btw. I would like to greet those people now. Finally the exams are over and I wanted to share one of my projects with you.
Lately Biomedical engineering is getting more and more popular, the emerging technologies made this field change rapidly. So I gave it a try, why not?

This article should teach you how to build a simple heart monitoring device, ECG/EKG (electrocardiograph). In the United States and Worldwide million’s of people are losing their life because of heart failure. It is a disease that comes with diabetes, stress and etc. Before I continue to explain what I did, I would like to WARN you! 500mA (miliAmps) on 220V will completely destroy your nervous system (so run it from battery supply), check everything twice and you are responsible for it on you own. OK! I think I can continue. There was a student job which I wanted in the Biomedical field, so to make my CV look even better I wanted to have something from this field so I built an ECG. First what I did was I went to and looked for similar projects and I found a great number of similar projects. Some were for logging data of heart disease patients, some were for some futuristic health monitoring devices and some were just for fun, as mine.


Let’s start with the definition what ECG is all about (taken from Introduction to Medical Electronics Application by D. Jennings, A. Flint, BCH Turton, LDM Nokes):

“The human heart can be considered as a large muscle whose beating is simply muscular contraction. Therefore contractions of the heart cause a potential to be developed. The measurement of the potential produced by cardiac muscle is called electrocardiology.

The depolarising field in the heart is a vector which alters its direction and magnitude through the cardiac cycle. The placement of the electrodes on the surface of a patient determines the view which will be obtained of that vector as a function of time. The most commonly used electrode placement scheme is shown in Figure 1. Here the differential potential is measured between the right and left arm, between the right arm and the left leg and between left arm and left leg. These three measurements are referred to as leads I, II, III respectively. This measurement lead placement was developed by Einthoven who stated that through measurement of lead I and lead II the signal seen at lead III could be calculated. This is the most basic form of ECG lead placement: from this the various features of the heart’s depolarisation can be calculated. Clinically there is a range of lead placement schemes which incorporate limb leads and chest leads.

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