Electrocardiogram (ECG)
Useful links
Here is a link to a Google Doc with design notes, observations, etc. For more information, or for design files, contact me. My email is j6summers@gmail.com
Electrocardiogram
This thing measures the electrical activity of the heart. I made two models, one that runs off battery and another that stays connected to the host computer. I started this project, in part, to help out a friend who teaches physical therapy. My interest waned when I found out I would need FDA approval to sell them
Electrodes are commercially available
Three electrodes are used, two on either side of the chest and a ground on the belly. Pro tip: Shave spots before you connect
What to say here?
Data doesn't look bad, sometimes a bit noisy, sometimes a bit cleaner. The noise is related to the 60 Hz hum of my house wiring. Apparently, the human body acts as a pretty good antenna to pick up that signal
Notes about noise
The noise can be removed with an electronic notch filter. I got my filter design from a DIY website (Instructables, I think). I suspect that some work on the filter would improve its performance.
Another thing I observed is that the signal is affected by motions of the chest muscle. I guess that should be obvious, but it wasn't to me.
I used this on a stationary bicycle trainer. The trainer has cloth wrapped handlebars that absorb sweat. When both the user and the handlebar tape are sweat saturated, the handlebars make a great antenna for the 60 Hz electrical signal. Placing the hands on the bars under this condition introduces a lot of noise that the filter cannot handle. Sitting back with the hands off the trainer gives a much improved signal. I have not tried it with gloves on.