AW3 HR sensor is quite accurate.

edhchoe

macrumors 6502a
Original poster
Oct 28, 2011
822
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The top photo shows data collected by my AW3 and data calculated by Apple Activity App's Indoor Cycle program.

The bottom photo shows data collected by Polar H2 chest strap and keiser m3i bicycle which uses magnetic resistance.

The HR at any given moment was usually within ±2.

Average HR was 156 vs 153, Apple's number is 3 points higher.

The calories burnt were 228 Cal vs 204 Cal. Apple's estimate was about 10% higher.

Overall, I am quite impressed by the accuracy of AW3 HR sensor.

I do not enjoy wearing the chest strap because of obvious reasons. The watch on the wrist is much preferable. If the m3i bike app programmer can incorporate AW HR monitor into their app, I would not have to wear the chest strap at all. I will contact them someday about this.


*I started the exercise bike app after I started pedaling so the duration has slight discrepancy. The app is on iphone and it does not start automatically when I start pedaling.
The Activity app was programmed on my AW3 with the target of 225 Cal to burn.






 
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betabeta

macrumors 6502a
Jun 28, 2013
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Looks great, your chart looks complete, mine has missing data, so something is up with my HR sensor:( my AW2 charts look just like that, but not with the AW3. I’m sure it’s just movement since mine was a run, but my AW2 worked.
 

mntdewdan

macrumors newbie
Oct 2, 2014
11
6
Looks great, your chart looks complete, mine has missing data, so something is up with my HR sensor:( my AW2 charts look just like that, but not with the AW3. I’m sure it’s just movement since mine was a run, but my AW2 worked.
I had an issue on mine on a 5-mile hike I went on today. My AW 2 was always on point, so I almost considered not testing it, but today I did a run with another device I trust to compare it to and the AW 3 was really off. It said an average HR of 101, when my other device said 119. The numbers from the AW 3 didn't make sense (like saying ~70 BPM when I'm going uphill at a brisk pace on a hard part of the hike). I rebooted all my devices and am going to try again tomorrow, but in comparing the devices green LEDs, it seems like the series 2 are noticeably brighter than the series 3. Hopefully this is just a single fluke...
[doublepost=1506225917][/doublepost]I guess the LEDs are more variable than i was thinking so I don't think the old vs. new one is really any different anymore. I tested a few different times and each watch was brighter or dimmer at different times, so it must make adjustments to those lights. Maybe it got stuck in some low power mode or something when I first tested.
 

betabeta

macrumors 6502a
Jun 28, 2013
868
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I had an issue on mine on a 5-mile hike I went on today. My AW 2 was always on point, so I almost considered not testing it, but today I did a run with another device I trust to compare it to and the AW 3 was really off. It said an average HR of 101, when my other device said 119. The numbers from the AW 3 didn't make sense (like saying ~70 BPM when I'm going uphill at a brisk pace on a hard part of the hike). I rebooted all my devices and am going to try again tomorrow, but in comparing the devices green LEDs, it seems like the series 2 are noticeably brighter than the series 3. Hopefully this is just a single fluke...
[doublepost=1506225917][/doublepost]I guess the LEDs are more variable than i was thinking so I don't think the old vs. new one is really any different anymore. I tested a few different times and each watch was brighter or dimmer at different times, so it must make adjustments to those lights. Maybe it got stuck in some low power mode or something when I first tested.

I am seeing the same difference between my old AW2 and the new AW3. My AW2 was very fast updating heart rate numbers, if I was at 165 HR and slowed down, it would instantly show the lower HR. Now with my new watch, I do the same and it stays at 165 for some time before picking up the lower HR.

I think it’s possible that we are seeing a learning period, starts off with lower light, raises intensity if it has issues. I certainly hope the LEDs are not less intense on the new watch. Outside of that it could be a more aggressive lowering of the lights to help with battery on these new LTE models. If it doesn’t get better I’ll call support to let them know because I would like to set the adjustment to have better accuracy over saving battery.
 

mntdewdan

macrumors newbie
Oct 2, 2014
11
6
So I've had 3 hikes now and it's been wrong on all of them. Basically what is happening is it is in certain situations (it looks like when my heart rate is ~140) it halves it. There are lots of spots where it goes from 130-70 then to 150. When I compare to the other wearables (including my other AW 2) they all say 140.
 

edhchoe

macrumors 6502a
Original poster
Oct 28, 2011
822
276
So I've had 3 hikes now and it's been wrong on all of them. Basically what is happening is it is in certain situations (it looks like when my heart rate is ~140) it halves it. There are lots of spots where it goes from 130-70 then to 150. When I compare to the other wearables (including my other AW 2) they all say 140.
The contact area must be moving around on the wrist in your situation.
My 42mm sits snugly on my 6" wrist. I use silicone strap for working out and the watch sensor area is in full contact with my wrist all the time. I use 38mm strap on my 42mm because 42mm bands do not provide good fit on my small wrist.
 

mntdewdan

macrumors newbie
Oct 2, 2014
11
6
Maybe, but I doubt it since everything should be the same. I mean I am using the exact same band (swapped it to the new watch) on the exact same spot on my wrist to compare the AW 2 vs 3. Something I never ran into on the series 2.

I'm wondering if these grey circles have something to do with it. If you look at the back of the series 2, there are grey circles around the LEDs. They're also around the series 3 cellular, but the GPS only version is just black instead of the grey circles. I've tried tightening the band more that the other watch, but that didn't seem to make a difference. Apple support suggested resetting all the diagnostic data, so I did that and we'll see if that improves things. Otherwise it looks like I'll be returning it and sticking with the series 2.
 

edhchoe

macrumors 6502a
Original poster
Oct 28, 2011
822
276
I did another workout today and finally without my chest strap! I love it!






 
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Zxxv

macrumors 68040
Nov 13, 2011
3,558
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UK
109watts for 30 minutes is really low. Were you just playing easy? Thats all day pace. Not what I would call a workout. I use stages power meter on my outdoor bike.
 

edhchoe

macrumors 6502a
Original poster
Oct 28, 2011
822
276
109watts for 30 minutes is really low. Were you just playing easy? Thats all day pace. Not what I would call a workout. I use stages power meter on my outdoor bike.
LOL you got me there.
I am a skinny guy at 125lb. I stopped exercising for 8 months and just restarted exercising once a week. I never trained seriously though. but in my defense, that average includes first 7 minutes of warm up. LOL.
 
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betabeta

macrumors 6502a
Jun 28, 2013
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Yeah I see people get amazing accurate results cycling, but moving the arms when running is still causing my series 3 issues with how fast it updates or changes with my HR, it's off many times. I find I have to adjust the watch position more, never had to with S2, had great results running. Battery life is crazy good so I think it is a less aggressive light setting, if so I would trade battery life for better accuracy on runs in my case.

I don't know if I should return for another to see if got a defect or just deal with it and see if an update down the road helps.

I am liking the new charts, just frustrating when the old watch was getting better data.
 

richard371

macrumors 68030
Feb 1, 2008
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Don't bother exchanging it. I feel mine is the same too but not a deal breaker. Maybe it will get better with future software updates.
Yeah I see people get amazing accurate results cycling, but moving the arms when running is still causing my series 3 issues with how fast it updates or changes with my HR, it's off many times. I find I have to adjust the watch position more, never had to with S2, had great results running. Battery life is crazy good so I think it is a less aggressive light setting, if so I would trade battery life for better accuracy on runs in my case.

I don't know if I should return for another to see if got a defect or just deal with it and see if an update down the road helps.

I am liking the new charts, just frustrating when the old watch was getting better data.
 

mntdewdan

macrumors newbie
Oct 2, 2014
11
6
Don't bother exchanging it. I feel mine is the same too but not a deal breaker. Maybe it will get better with future software updates.
Do you have the LTE Series 3 one or the GPS only series 3 one? I'm wondering if there is a difference between the two in terms of the heart rate sensor. For example, my series 2 has grey circles (about 1/4" thick) around the LED lights, but the series 3 doesn't (and as far as I can tell the cellular series 3 does).

I did the same hike with my series 3 and series 2 on different wrists at the same time. (Switching about halfway through). You can see the series 2 works well the whole time, but the series 3 doesn't do well until the light gets pretty low at which point it matches perfectly. The series 3 data has a bunch of gaps as well (some minutes where it only recorded 1-2 records) whereas the series 2 is pretty consistent about reading the heart rate regularly. I just updated my series 2 to watch OS 4, so I will see if now it starts having issues as well.
Screen Shot 2017-09-26 at 9.12.39 PM.png
 

Zxxv

macrumors 68040
Nov 13, 2011
3,558
1,102
UK
LOL you got me there.
I am a skinny guy at 125lb. I stopped exercising for 8 months and just restarted exercising once a week. I never trained seriously though. but in my defense, that average includes first 7 minutes of warm up. LOL.
Its all good mate :) the watts stood out like a sore thumb, way more than the calories :D
Being light and skinny is ok. You can get real good at climbing hills and mountains with a low weight. Still requires some more watts, and a little (ha) suffering.

Keep at it as coming back wont last long, its the best bit if you ask me, the part of exercise where it hurts more by doing less haha
 
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richard371

macrumors 68030
Feb 1, 2008
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Lte

Do you have the LTE Series 3 one or the GPS only series 3 one? I'm wondering if there is a difference between the two in terms of the heart rate sensor. For example, my series 2 has grey circles (about 1/4" thick) around the LED lights, but the series 3 doesn't (and as far as I can tell the cellular series 3 does).

I did the same hike with my series 3 and series 2 on different wrists at the same time. (Switching about halfway through). You can see the series 2 works well the whole time, but the series 3 doesn't do well until the light gets pretty low at which point it matches perfectly. The series 3 data has a bunch of gaps as well (some minutes where it only recorded 1-2 records) whereas the series 2 is pretty consistent about reading the heart rate regularly. I just updated my series 2 to watch OS 4, so I will see if now it starts having issues as well.
View attachment 722478
 

musicpenguy

macrumors 68000
Oct 29, 2006
1,599
570
I’ve noticed my series 3 not collecting enough data to create the graph on a run and a swim, haven’t had issues before with my series 0 for runs, curious what I’m doing wrong, same band as before, maybe the case thickness is making it less accurate for certain sessions?
 
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mntdewdan

macrumors newbie
Oct 2, 2014
11
6
I’ve noticed my series 3 not collecting enough data to create the graph on a run and a swim, haven’t had issues before with my series 0 for runs, curious what I’m doing wrong, same band as before, maybe the case thickness is making it less accurate for certain sessions?
@musicpenguy did you have the LTE or the GPS only version? I have the GPS only version.
 

mntdewdan

macrumors newbie
Oct 2, 2014
11
6
Ok. So tonight I tried my series 2 watch on watchOS 4 after I upgraded it (the one in my previous post with the comparison graph that starts "Do you have the LTE Series 3..."), and it appears to have similar issues as the series 3 watch. Not quite as bad, but still underreporting a significant portion of the time close to sunset. This leads me to suspect it's a software issue. Hopefully that means it will/can be resolved in the future. Looking at my history of HR data over activities, it seems like it was improving the longer I had worn it. Do you all have the same experience? Does it seem to be getting better over time?

Screen Shot 2017-10-03 at 9.18.21 PM.png
 

iPhysicist

macrumors 65816
Nov 9, 2009
1,333
971
Dresden
Yesterday I die a run with my S0 (with phone zwing watch app) and had dropped readings for the first 2km. Prior going into second lap I decided to cover the watch with my sleeve and I had increasing accuracy for some time and shortly afer it stopped dropping readings. (And I did not check the watch during second lap). I was running after sundown so I would rule out and influence by other light sources.
After I finished my run I walked 5 Min and I had dropped readings for the cool down again.
 

dwsolberg

macrumors 6502a
Dec 17, 2003
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546
So I've had 3 hikes now and it's been wrong on all of them. Basically what is happening is it is in certain situations (it looks like when my heart rate is ~140) it halves it. There are lots of spots where it goes from 130-70 then to 150. When I compare to the other wearables (including my other AW 2) they all say 140.
Weird. That’s the same issue I used to have with my original Apple Watch, but after an update a while back, it now works much better. I’m not sure what to make of the regression.
 

dypeterc

macrumors regular
Mar 5, 2012
147
113
Yesterday I die a run with my S0 (with phone zwing watch app) and had dropped readings for the first 2km. Prior going into second lap I decided to cover the watch with my sleeve and I had increasing accuracy for some time and shortly afer it stopped dropping readings. (And I did not check the watch during second lap). I was running after sundown so I would rule out and influence by other light sources.
After I finished my run I walked 5 Min and I had dropped readings for the cool down again.
It’s not a light leak issue rather a physiological one. When the wrist or arm is cold and your just starting a run (or ride) the body is shunting blood to the core and legs. The capillaries in the arms also construct further reducing the hr sensor’s ability to pick up a signal (i.e. blood passing by). Once properly warmed up the sensor can pick up and lock onto and obtain an accurate consistent hr. Not sure what’s up with WatchOS 4 changing the way it reads hr data... I’m on S0 and WatchOS 4 and get great data on my trainer rides.
 

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BillGates1969

macrumors 6502a
Sep 11, 2008
605
515
Bournemouth
AW S3 here. I needed to go to the doctor recently, and he needed to take my pulse. I checked the AW against his contraption and it was spot on to the beat. Even when I held my breath for a few seconds to raise it a few notches, both the the AW and the doctor's reader raised the same amount. He was really quite impressed and said he never had had a patient compare their watch against his equipment. I think he really meant to say he couldn't believe how geeky I was comparing the watch to his equipment :) Although he did then proceed to check my stats from the Activity app as I have a chest infection and was getting random shortness of breath.
 
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