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.

[mpls-gtr]

Welp this doesn't bode well...  I just came to checkout the Sense forum to see if the HR monitor works any better than the Charge 4 and this is the first post I see.

My Charge 4 and a bunch of others' in a thread in that forum are all having the same issue with the HR monitor not working during high impact exercise.  Mine, for example, drops from 145 to 75 while on the treadmill, almost every time.  I think it's because it moves slightly because of moving and sweating.

Anyway, it's super frustrating when you have to check it every minute or two just to see if it's reading correctly.  And if it isn't, it's 5+ minutes of moving it slightly, waiting to see if it gets a reading... Nope, move a tiny bit, wait... 

It sucks while you're trying to focus on working out and having to mess with it.  But if it's not reading correctly, then bad data gets synced and if you're using the Fitbit app to track your health how can you trust what it's showing you?

Anyway, the Sense is supposed to have upgraded Heart Rate monitor hardware so doing some research to see if it works better than the 4... Cause I'm not gonna drop $300+ for another over priced step counter.

[Rich_Laue]

Most people are finding it pretty accurate,

YouTube reviewers agree. 

What factors can affect my heart-rate reading on my Fitbit device?

[jumper0888]

DO NOT GET THE SENSE. HR is brutal. When lifting weights it’s off 20-30bpm. Running doesn’t seem too bad.  Might go back to my Versa 2

[t.parker]

@Rich_Laue the problem with YT reviewers is that they didn't pay for my watch which apparently doesn't work for me when it comes to HR 🙂 Everyone looks at the individual case because that's really the only one of any concern. I don't think the argument "youtube reviewers agree" is very convincing 🙂

@mpls-gtr remember that you can always return the product in case it isn't functioning the way it should. Personally, I go for a refund rather than replacement as a replacement doesn't guarantee any improvement, and if any improvement will come up at a later time nothing stops me from buying the watch again. Buy, thoroughly test, decide - keep it/return it.

[Mateos]

I think that the HR issues of the Sense are one of the most discussed topics on this forum. Many (maybe not all) users experience that the Sense does not measure their HR very well. It is also something I experience and why I have actually gone back to the Charge 4. My FB Sense is currently collecting dust in the hope that a new firmware update resolves the issue. 

I do not recognize that many YouTube reviewers find the HR sensor of the Sense reliable. DC Rainmaker called it a "dumpsterfire", DesFit said he got the watch but was not going to make a video about it because of the HR issues and The Quantified Scientist said he discovered "some serious issues" with the HR sensor of the Sense.  

I am not trying to bash the product because I actually like the watch, but I am disappointed that Fitbit does not recognize the problem. The HR issues make the Sense useless as an activity tracker for many users. 

[Giampi71]

Unfortunatelly I actually disagree @Rich_Laue, as the greatest part of the posts in this board are to complain about HR and almost all reviewers stated the same.

On top of mind 2 of the most qualified reviewer DC Rainmaker and The Quantified Scientist have been very vocal about it. Here it's my personal, although not so reputed, test

EDIT: Sorry @Mateos I just realized my post is almost a copy of yours.

[Mateos]

No problem @Giampi71 ‌‌Just more proof that we need Fitbit to acknowledge and solve this matter!😃

[pmmegan]

I have not opened my Sense box delivered yesterday and probably won't based on what I reading here. HR 24/7 monitoring was my primary reason for buying this watch. I have AFib from time to time but it is always preceded by an increase in HR. If this watch is not accurate it's useless to me.

[Mateos]

@pmmegan Just give it a try. You should have a trail period and I would use that. I experience the problem, especially during exercise (together with many others) but it is also fair to say that there are people who indicate that hr tracking is working fine for them. The accuracy depends on many factors and may differ from person to person (at least that is what I understand - I am not a specialist nor a doctor).  And also remember that the Sense is not meant as a medical device.  So just give it a try and send it back within the trial period if it does not work for you. 

[Basandy]

@pmmegan  I agree with @Mateos, it is worth trying the Sense. I own one and find the HR Sensor performance works well for me and is relatively accurate during daily use and for exercise (albeit with a slight lag in getting to higher heart rate zones). 

[blenderbender]

So I just chatted with Fitbit CS and this is primarily the gist of the chat in reference to the inaccuracy of the Sense HRM as compared to my Polar Chest Strap...... "Let's start with me (chat agent) suggesting that is not appropriate to compare your Sense heart rate information/ monitor with a different device (Polar Chest Strap in this case) since they use a different technology from each other."

WTF? Heart rate is heart rate no matter what technology is used to measure it. There has to be a benchmark to compare to. Then I was advised to restart my Sense, see if that made any difference, and get back in touch if there was still an issue. 🤐 I'll keep the bad language to myself 😁

[Bauer24]

Two main features of this watch are the HR sensor and the GPS. NEITHER WORK! Literally every other feature I could do with out. What’s even worse is Fitbit don’t care nor are they interested in your feedback. Try and message James Park on Twitter... he will block you.

[Rich_Laue]

@blenderbender your chest strap is looking ate the actual electrical signals that control the the heart. 

Your Fitbit is looking ate the changes in the volume of blood in your arm. 

The two units use completely different technology. 

[Giampi71 · Accepted solution]

@Rich_Laue yes the two technologies are completely different but are measuring the same entity (in this case heart rate) hence it is definitely legitimate compare the results. It is like when you weigh a body you can use a scale (hence technically measuring the mass of the object) or a dynamometer (hence measuring the weight, aka the force the body is attracted to the center of the earth); two completely different system but at the end, to be useful, need to provide the same result.

Now back to the topic.

Fitbit decided to adopt exclusively the optical heartrate sensor and in fact it is not possible to use any external sensor. This means Fitbit is really confident about the reliability of the results given by its Purepulse 2.0 (the sensor used in Sense/Versa 3).

Below is my test

Comparison: Fitbit Sense (left wrist), Fitbit Charge 4 (right wrist), Polar Vantage V (right wrist), Pixel phone reading Polar H10 chest band 

You can see that Polar optical sensor matches almost identical the reading of the chest band (so yes, it is definitely possible to compare measures from different sensor type), Charge 4 (using the old type sensor) is definitely good until 35 mins (a problem that I find quite often in Charge 4, probably the different sweating level affect the reading) while the Sense (using the latest HR sensor by Fitbit) is completely wrong (up to 40 points difference, the average reading provided is higher than the maximum heart rate)

[Bauer24]

If I could downvote. I’d downvote the hell out of this. I have yet to come across a single review where it says it’s accurate. In fact nearly every review have said it’s the most inaccurate they’ve come across. 

[Bauer24]

I’m baffled!!?! If I jump on a scale by Apple and it says I weigh 10st but then I weigh myself on a Fitbit scale and it says I weigh 15st.

According to Fitbits logic they are both right. And because of this. We really need to stop buying Fitbit products. When you refuse to admit there’s a problem. The only option left is to stop buying their products. 

[Rich_Laue]

When I jump on the scale in doctor office 1 then jump on the scale in office 2, they also don't agree. 

[Basandy]

I am not for one moment saying that you do not have an issue with your Sense, however it is worth considering that there are a number of users, me being one of them, who can state the watch performs well for them. I use the Sense for daily exercise (treadmill, elliptical and exercise bike) and the watch tracks my heart rate on a consistently accurate basis when compared to my previous Apple Watch and Inspire 2. 

I do not know if there are batches of faulty HR sensors or any other factor involved, however I personally like the way in which the Sense performs as a daily health tracker. I for one would purchase another Sense if I had to. 

[t.parker]

@Rich_Laue there is a big difference between such comparison. The HR can be measured by multiple sensors in exactly the same time and under exactly the same conditions. Did you even look at @Giampi71 data comparison? What is your opinion on that?

1) all sensors are wrong

2) only Sense is right

3) only other sensors (including C4, which seems to be aligned with two others for most of time) are right.

There is no really any other option. Everyone has just one heart and at a single moment it either generate beat or not. It is fully measurable data. Why would comparison make no sense in that case? There are lots of things for which comparison makes not so much of sense, like sleep data which cannot be really verified unless you go under sophisticated equipment which could be use as a reference. But HR is not one of those things.