Can I get some help with a few questions I have about Heart rate monitor fluctuations?

[Stockmoose16]

Heart rate monitor fluctuations

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[gadgetrants]

Re: Heart rate monitor fluctuations

Hey Jonny welcome to the forum! :smile: Good question...my hunch is that if you're pressing the Power button (which displays the "Me" tile, including your HR), that may wake the HR monitor from sleep and cause it to scan for a signal. Not totally sure about that though, since tapping the Me tile and scrolling to your HR (far right) will then force a new HR reading -- you can tell because it displays "Acquiring" vs. "Locked"). It seems as though tapping the Power button alone is only half the process of getting a new HR reading.

If my guess is right, then there'd be no way to confirm (without pressing Power) that it's in fact sleeping for every 9 minutes. Wait, that's not right...you could use the WinPhone app that polls the Band sensors continuously, but with that I think all bets are off.

-Matt

 

[DroidUser42]

Re: Heart rate monitor fluctuations

Hmmm. That makes sense. The Band displays what it thinks is the HR at the moment (or last reading), but won't record it unless locked. And I know when you do activate the HR function, it takes time to lock-in and even then it takes time to settle down.

 

[James8561]

Re: Heart rate monitor fluctuations

The band acquires heart rate every time you turn it on to me tile with power button.
So every time you press power button, band will take heart rate.
Source: me peeking at the green LEDs of the HR sensor.

 

[defante]

Re: Heart rate monitor fluctuations

The band acquires heart rate every time you turn it on to me tile with power button.
So every time you press power button, band will take heart rate.
Source: me peeking at the green LEDs of the HR sensor.

To clear it up more, it tries to acquire a heart rate (hollow heart) when the power button is pressed, but it won't record a reading until it gets a lock on your heart rate (solid heart).

 

[gadgetrants]

Re: Heart rate monitor fluctuations

Excuse my know-it-all tone but...certainly what the rep told you was buls***. 100% second-guessing -- for sure front-line phone support doesn't get the secret sauce recipe. I'm not sure my earlier comment was clear so let me put it this way: you can't view your HR on the Me tile unless you tap the Power button, and I think doing so puts the Band in a power state somewhere between "completely ignore HR signal for the next 9 minutes" and "update HR now". In other words, if you can see a number on your display, it's not in the "do nothing for 9 minutes" state.

It's still an open and interesting question why any number shows up there, and why intuitively it isn't an up-to-the-second HR reading? Again, we can only guess. I've made several comments in earlier posts (so I won't repeat myself!) that amount to the following: capturing a HR estimate via infrared is a pretty challenging problem, and maybe that "not-yet-locked" number could be one of the following:

(1) A low-resolution "pre-reading", i.e., using low-powered or slower-resolution sensing

(2) A time-based estimate, based on recent readings and knowledge of Band movement

(3) A full reading, but with a low-confidence value assigned since the signal is noisy (e.g., too much wrist movement).

If you'll indulge me one more thought: it's important to remember what it means for the signal to lock...basically the algorithm says, "Don't say 'locked' until condition XYZ is met." My suspicion (my own area of work is not far from these issues) is that "locked" probably means "repeat the HR reading X times, and if the variation in X readings is under some threshold, then report the average as the 'locked' HR." So the moment it begins collecting IR image data it has an estimate (maybe that's the odd number you see) but it doesn't lock until the estimate converges to a stable value.

​-Matt

 

[gadgetrants]

Re: Heart rate monitor fluctuations

The band acquires heart rate every time you turn it on to me tile with power button.
So every time you press power button, band will take heart rate.
Source: me peeking at the green LEDs of the HR sensor.

Doh, you're a genius. Why didn't I try that???? LOL

-Matt

 

[DroidUser42]

Re: Heart rate monitor fluctuations

When you pull up the HR on the display, I'm pretty sure the first thing that will appear is the last HR reading in memory. (It comes up too fast to measure a heart beat which may only happen about once a second.) It will also turn on the HR sensor (the green LEDs inside the clasp) and work to get your current HR.

I'm not entirely sure what "locked" means. But in my experimentation, it seems that attempting to sense HR on the arm when there is any motion is a tricky task. Motion tends to introduce "noise" or false pulses. I think "locked" is when the Band thinks it has identified what is heart beat and filtered it out from other things (such as surges of blood flow due to motion.) Since a running step can be in the same "pulse rate" range as a heart beat, I'm not sure how they do that. That must be part of their secret sauce. (But I suspect they use the motion sensors and try to reject things that sync with motion.)

From what I've seen, while "locked" is better than "unlocked", it's by no means infallible. I can see that when it says its just acquired a "lock" but then over the next few seconds the displayed number will change by 10+ when there is zero change in my activity. But once it's locked and stays locked for about 5 seconds or so, it seems to be about as good as you're going to get.