Most recent activity
-
The heart rate monitor in the bangle2 doesn't give realistic data, so (being a curious person) I'm trying to understand how it works and what the problem is. I understand the HRM is affected by movement, but I can't find more details how the algorithm works and what kind of movements are the issue.
I also have a Garmin watch which I wear for testing on the other arm, and this generally gives realistic values. They don't match the data from a belt exactly, but are generally in the right range and go up during exercise etc.
But the Bangle HRM really only gives realistic values when I'm totally at rest. In particular, when cycling the measured HRM mostly just jumps around and I even get totally mad rates like 30 when it should be around 150.
As I understand, the HRM is essentially a Photoplethysmograph, so it measures the reflected/scattered light from the LED which is modulated by the blood flow and other factors.
I guess then the algorithm tries to find the peaks in the scattering and determine the dominant frequency. Is this simply counting the peaks, or does it do some kind of Fourier analysis?
Movement can easily produce artificial peaks, but do we understand the mechanism a bit better? Is it the movement of the sensor against the skin (so that different parts of the skin are measured), or does movement and vibrations change the actual blood flow at the wrist?
I noticed two particular things:
When cycling, my hand is not really moving much as it's on the handle bar, so are just the vibrations from the road enough?
I tried to stop a few times, waited a minute and hold the hand very still, but the HR is still almost random. How long does the monitor typically to take good measurements? Or is there something else going on that it doesn't handle higher HR very well?
Thanks! I had not seen that thread, sorry.