DIY ECG with 1 op-amp

I made surprisingly good ECG from a single op-amp and 5 resistors! An ECG (electrocardiograph, sometimes called EKG) is a graph of the electrical potential your heart produces as it beats. Seven years ago I posted DIY ECG Machine on the Cheap which showed a discernible ECG I obtained using an op-amp, two resistors, and a capacitor outputting to a PC sound card’s microphone input.

DIY ECG with 1 op-amp

 

 

It didn’t work well, but the fact that it worked at all was impressive! It has been one of the most popular posts of my website ever since, and I get 1-2 emails a month from people trying to recreate these results (some of them are during the last week of a college design course and sound pretty desperate). Sometimes people get good results with that old circuit, but more often than not the output isn’t what people expected. I decided to revisit this project (with more patience and experience under my belt) and see if I could improve it. My goal was not to create the highest quality ECG machine I could, but rather to create the simplest one I could with emphasis on predictable and reproducible results. The finished project is a blend of improved hardware and custom cross-platform open-source software (which runs on Windows, Linux, and MacOS), and an impressively good ECG considering the circuit is so simple and runs on a breadboard! Furthermore, the schematics and custom software are all open-sourced on my github!

he circuit is simple, but a lot of time and thought and experimentation went into it. I settled on this design because it produced the best and most reliable results, and it has a few nuances which might not be obvious at first

For more detail: DIY ECG with 1 op-amp

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