ECG

The circuit can be very simple, using just a few op-amps and other basic components. To make it useful, we need to display the signal either using an oscilloscope or a computer with custom software and a viable sound card.

Electronics stuff

A possible circuit to copy: https://courses.cs.washington.edu/courses/cse466/14au/labs/l7/l7.html

Measuring hyooman stuff:

ECG: common artefacts and how to avoid them https://www.youtube.com/watch?v=VsZLtW5aSfU EKG/ECG Interpretation (Basic) : Easy and Simple! https://www.youtube.com/watch?v=FThXJUFWUrw