Heart Rate Detection While Not On Wrist

Was the heart icon flashing? If so then it's not got a heart rate. If the icon was solid then there is something up

CW

I don't think Garmin's Elevate HRM knows when the sensor is pointing at blank space

For one, the charge HR knew when it wasn't able to pick up a heart rate and it would display -- on the screen instead of guessing. My feeling is because the 235 can't properly detect when a heart beat is present it often reports that I am sleeping during times when I am not actually wearing the watch.

The problem is that Garmin's Elevate optical HRM (for whatever reason) does not know it is not picking up a heart rate when there is nothing pressed against the LED sensor. Lay the FR235 on a towel or some such, then start the Heart Rate widget. The heart icon will flash, and then the heart rate reading will go to 71 or 72 and the heart icon becomes static – as it's obviously been programmed to do, no matter what the sensor is or ought to be telling the watch, and that has been the subject of many complaints of this ‘bug’ – but after about 10–15 seconds the heart rate will be displayed as ––. However, that does not happen if you just hold/hang the watch up in the air with empty space behind the sensor. In fact, when the heart rate is displayed as ––, simply removing the watch from the towel and holding it up will see that the heart rate reading go to 71 or 72 (with a solid heart icon) within moments.

My feeling is because the 235 can't properly detect when a heart beat is present it often reports that I am sleeping during times when I am not actually wearing the watch.

Were you charging the watch at night? I know I've seen the watch report that I was sleeping from the moment I connected it to the charger (at a time that was during the normal bed time specified in my user profile) to the moment I disconnected it, even though I didn't go to bed for another couple of hours after I connected it, and didn't get around to disconnecting it for half an hour after I woke up. I'm starting to think that Garmin's engineers have simply decided that, as a best guess in the absence of other information, the user is sleeping if the watch is being charged (or just not being worn?) during the normal bed time. (Obviously, if it detects the event of the watch being connected to the charger, I must've been awake at the time and most likely awake before that.)

Individual opinion as to whether the watch (or the fitness platform) ought to err on the side of under-reporting sleep instead of over-reporting sleep may vary, but either way error is inevitable due to the design fault of not being able to say when it simply doesn't know.

Overall I am very happy with my 235 but I too have some problems with it. One thing I've noticed is that the 235 tracks a heart rate even when the device not being worn.

Coming from the fitbit charge HR I had some expectations as to how this device would work but there are things that the fitbit did better. For one, the charge HR knew when it wasn't able to pick up a heart rate and it would display -- on the screen instead of guessing. My feeling is because the 235 can't properly detect when a heart beat is present it often reports that I am sleeping during times when I am not actually wearing the watch. The fitbit on the other hand was almost perfect at knowing when I was asleep vs. simply having removed the watch.

After the most recent update this is what my 235 shows on the screen while holding it up in the air - http://imgur.com/a/8lfq6

What you see is the heart rate counting up from 73 to 79 - while being held in the air! My finger was not touching the sensor in any way.

I noticed this as well, I found that it would stop finding the HR if I held the straps by the ends rather then close to the HRM. Also keep the lights away from anything reflective then I saw it go --. The oHRM sensor seems to be picking up some faint signal from something it probably shouldn't be.

It'd be interesting to see the actual raw data that its picking up to know if this is a HW problem, or something that actually can be corrected for. Depending on what data the HW is actually reading it may not be possible to correct for it afterwards.