Sense heart rate monitor is not accurate

[blenderbender]

I've been feeling the heart rate monitor is way off on my Sense and just proved it today pitting it against my Polar chest strap monitor. It's way off (low) over 15% on the way up and though the difference is less on the way down it's still significant. Is this usual and is it anything that can be addressed? I should have known, paying more for all the silly bells and whistles and the most important feature isn't even close to being accurate. Who gives a flying ____ about nighttime skin temperature.

Moderator edit: updated subject for clarity.

[Rich_Laue]

Both support and my point is that they do not use the same technology to measure. Each with their unique problems. 

[t.parker]

@Rich_Laue so how do you know which result is correct if you get different results from Sense and Charge 4 (like on @Giampi71 test)? What is your reference for data validity. It isn't logically possible that C4 and Sense in the case above are both right. If it isn't possible to tell if data is correct then what would be a use of such data? Why even bother with HR sensor if one denies possiblity of validation? 2+2 is always 4, doesn't matter if you count it on your fingers, write it on the chalkboard or use a calculator. Am I wrong?

[blenderbender]

Not sure what your point is.... it only means they are not calibrated to the same standard.

[Mateos]

@Rich_Laue Slight variations due to different technologies I can understand, but consistenly under or over reporting 30 hrbpm during exercise frankly is rediculous. I am really disappointed by Fitbit's lack of response to this topic. By not responding at all to these substantiated complaints, I can only conclude that Fitbit does not value me as a customer. Luckily, the retailer I bought the Sense from, is prepared to take it back and give a refund. So that is what I will do today. I can accept the flaw if there was some sort of outlook that they are working on a fix in their next firmware update. But nothing, they leave us completely in the dark. For the moment I will go back to the C4 I still have and use the premium subscription. Hopefully, Google can set things straight, but otherwise I won't easilly be tempted to buy another FB device. 

[bobby2478]

I have exact same experience as @Mateos , spent over 30 minutes doing intermediate cardio workout DVD where I was out of breath for the entire workout and it started off fine going up to 155-163 BPM, then suddenly crashed down to about 95 and wouldn't go above 115 BPM for the remainder of the workout. This isn't the first time either. Every time before I workout I've gone to the extent of restarting my Sense to see if that made a difference but nope.

Considering one minute I was over 145 BPM, the next minute (still out of breath) it dropped to 115 and wouldn't go above that (hovering beteen 95-105 most of the time) it's easily off by 30-40 BPM. Completely ridiculous. Drastically undercounts my Active Zone Minutes. I preordered back in September so can't return and am stuck with it. Just ticks me off now that I want to actually improve my health and am working hard only to see the core feature (HR tracking) is basically worthless. I even shaved my arm hair under the Sense so it couldn't interfere but nothing. Not sure if when I started to sweat this suddenly threw it off, it's odd how it was fine to start the workout but then was off for 1/2 the workout.

At this point I'd rather have a Charge 4. It's been over 4 months since launch and Fitbit still hasn't bothered to issue a firmware update to fix this.

[Min1920]

So I am doing Insanity Max 30 and I die during the workouts. But I find it strange that even in those moments the Charge 4 for a long period of time show my H.R. is under 100/min. Yet when i am walking fast the tracker shows a much higher H.R. for a longer period. So I think it's probably more suited to running and walking rather than these HIIT workouts.

[ComeOn]

When doing high intensity cardio in between weight training sets. I know my HR is maxed out. I look at my sense in workout mode and it has my heart rate at 95. So, I know it is not real-time accurate. If I am just using average heart rate values that defeats the purpose of determining what zone I am in. Pretty disappointing for $300. I did not have that problem with my Ionic.

[SunsetRunner]

Heart rate monitor not even close. Walk several flight of stairs every morning and then check HR with vital sign machine on my unit. The Fitbit Sense say 90-95 when my Heart Rate is 130's. Disappointed this will be first and last Fitbit. Also, oxygen is averaged overnight not on demand, what good is that?  

[mc9471]

Today, I hit 150 bpm according to my chest belt but the Sense didn't make it over 80. That's pathetic. Strangely, I stopped the workout and started a new one, and the second time the Sense actually tracked the belt monitor pretty well. Sometimes this works, sometimes it doesn't.

[AtsukoArai]

I loved my Versa 2 until one day like a month after I got it the screen just stopped working. Now I get the Sense thinking “surely they must have fixed the problems in this new version” but no, HR monitor still blows. Sent it back. Not paying $300 for a step counter, it doesn’t even measure steps and floors accurately. Waste of hard earned money. 

[TommyIzzo]

@AtsukoArai Wasn't the Versa 2 under warranty when the screen stopped working after a Month?

[DMel08]

The Quantified Scientist performed a scientific heart rate review on the Sense and came up with similar findings https://www.youtube.com/watch?v=qt7hBdddCrw

[davestracker]

I too had this issue started today with the Fitbit Sense.  I was exercising and I usually get around 130-160 during HIT but for some reason today I was stuck at 80-90.  So bummed to hear all the issues with how bad the HR sensor sucks.  Now that Google has taken over Fitbit I'm sure this will get even worse and probably make it to the Google graveyard soon.

[DMel08]

It's ok for measuring resting HR although it lags my pulse oximeter by a few seconds. I don't have AFib but sometimes my HR will speed up unexpectedly. This happened once while wearing the sense and I was instantly alerted by the watch which showed the elevated rate. 

[TommyIzzo]

@DMel08 Mine supposedly went into cardio zone just getting up for a drink of water at night. Heart rate jumps around a lot on Fitbits. That's mainly why most don't like the zone alerts. The other day, my heart rate dropped 30 BMP while I was glancing at the watch. I don't think it was my heart. 

[deiG]

Sense's heart rate is usually off. 

[AtsukoArai]

Yes, they took it back without question. They offered a replacement but I didn’t want one, I want my money back. 

[Thook]

I agree. I got my sense for Christmas and suspected the hr was off when lifting weights. Well I have transitioned to cardio this cycle and the watch is a joke. The hr delay is 15 minutes before I get any decent reading and it takes me 30 minutes into cardio to register somewhat close. Now this is compared the different cardio machines with integrated hr systems. I have been exercising for decades and known my  hr and the watch rarely matches up. I am very close to returning and would never recommend. I just found this thread as I have been trying to figure out why mine is off but obviously it is a systemic problem.

[AtsukoArai]

From a software developer standpoint, I really think that the problem lies in the device’s programming rather than the hardware itself. I have a lot of experience troubleshooting applications to notice that when I am not specifically doing an exercise (that is, I have not pressed the exercise button and chosen a workout and started it), the water is almost perfectly accurate. So my conjecture is that there’s something happening in the exercise program that’s severely interfering with reporting the data from the heart rate sensor, as it has a timer running, it’s probably actively tracking steps, elevation, GPS coordinates; they NEED to test their software better before charging people through the nose for a device that can’t properly do pretty much the most important reason people buy this thing.

Sent from my iPhone

[DargieFit]

I’m here today obviously because I’ve noticed my heart rate is very low compared to my Fitbit Ionic which I just upgraded to the sense in Dec. I have try adjusting where the watch sits on my wrist. Tried adjusting the strap tighter and looser. Nothing works. When I’m in the middle of a HIIT workout and I know my heart rate is above 140 BPM and my Fitbit is showing 110 I push the face of the watch down firm on my wrist ( I wear on inside of wrist right over the artery) and my heart rate immediately jumps up 10 or more BPM. I’ve had the Fitbit charge 2 as well as the versa and ionic and ALL were way more accurate with heart rate monitoring than the sense. I work out 7 days a week and more than have of them of HIIT and the heart rate is so inconsistent.