HRM accuracy while resting

[Milanese44]

Hi everyone
I just got my bangle.js 2 and have been figuring out some stuff the last couple days. I love the product and the ability to program personal ideas!

However one thing that confuses me a bit is the HRM. I know there are many discussions about this, but the thing is, for me it seems to be quite accurate a lot of the time. Yesterday I tried it on a run and I never saw an unexpected value. It also seems to adjust well to sitting or walking. What I have noticed however is that while sleeping, the HRM behaves much worse. Im getting about 90bpm for extendet periods of time at night (~50min) when my resting heart rate should be around 50-60 bpm. Does anyone have similar experiences?

I havent done much testing about why this is, but from just running the live HRM it seems to me the way the bangle is oriented influences how well the HR is measured. Does anyone have an idea if this is a known problem?

I was thinking about logging acceleration data, HR and confidence level and see if there is a pattern, but since im new to this that will take me a while probably.

Thank you for any insight you might have and if you know an app that does these logs already let me know please ;)

[Milanese44]

Ok small update: I have gotten the mentioned data but I cant see any correlation. I will still post it here in case anyone wants to look at it

Next step I guess has to be to make sure the HRM ACTUALLY isnt correct by comparing to another device and then I will also try logging the actual HRM measurements to maybe see something but it doesnt seem to be an issue of "health" choosing the wrong measurement but the sensor returning weird measurements.

[Milanese44]

In my experience, it's really easy to get movement below 400 no? In the logs I've taken I think every instance was <400 haha. From the plots you can see that at these instances z was actually almost exactly -1 so it does seem to add up.

[gfwilliams]

If you dump a CSV file from the health app, what movement values do you see when the Bangle isn't being worn, and when you're sleeping? I'm seeing between 60-80, so we could probably drop the threshold down to 100 safely?

[Milanese44]

Yeah mine are also always below 100, highest being 96 though. While sleeping the values range from 72 to 424.

[gfwilliams]

I've just pushed a change to the development app loader than puts the threshold at 100 - I'd be interested to see if this helps?

[Milanese44]

Nice! I've updated the app, will log data over night again and give an update tomorrow.