The Do-It-Yourself Electrocardiogram | SpringerLink
Homemade sound card ECG circuit
DIY Arduino-Based ECG System - Circuit Cellar
DNN Based Homemade ECG - Hackster.io
6. The schematic of the ECG circuit. | Download Scientific Diagram
Electrocardiography for Cheap: DIY ECG Uses One LM741 Op-Amp, Five Resistors, and 'Penny Electrodes' « Adafruit Industries – Makers, hackers, artists, designers and engineers!
Citizen Science — DIY ECGs - Make:
Build Your Own ECG-EKG Unit | Nuts & Volts Magazine