Bangle.js doesn't actually have an ECG - it's an optical heart rate sensor - so you wouldn't actually expect to get a really spiky ECG-like signal out of it anyway. It's one of the reasons Bangle.js normally uses autocorrelation, which allows it to pull a repetitive signal from the noise.
The sensor itself is analog so I'm afraid short of physically changing hardware there is no way to make it more powerful.
Having said that, if you look at your Bangle you may find that by unscrewing the back (https://www.espruino.com/Bangle.js+Disassembly) and carefully applying some foam to the window at the back to mask off between the LED and photodiode sides of the sensor, you might be able to get it working a bit better than standard.
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
Bangle.js doesn't actually have an ECG - it's an optical heart rate sensor - so you wouldn't actually expect to get a really spiky ECG-like signal out of it anyway. It's one of the reasons Bangle.js normally uses autocorrelation, which allows it to pull a repetitive signal from the noise.
The sensor itself is analog so I'm afraid short of physically changing hardware there is no way to make it more powerful.
Having said that, if you look at your Bangle you may find that by unscrewing the back (https://www.espruino.com/Bangle.js+Disassembly) and carefully applying some foam to the window at the back to mask off between the LED and photodiode sides of the sensor, you might be able to get it working a bit better than standard.