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Optical Heart Sensor accuracy - why is so bad?

Former Member over 7 years ago

Hi all! I just brought my 645M to the first training. The main reasons i bought this one, was optical heart rate sensor (i hate wearing the strap) and of course music. As we all now, music for now is incomplete (no Deezer), but after reading some DCRainmaker test i was full o hope that the optical sensor can replace my HRM strap. It looks that i was wrong. I took my new and shiny 645 for some interval running (10x400), and the result is poor (comparing to the HRM with my old Fenix 2). Take a look at the screenshot, is it normal? For me there's no changes during interval or rest time. This is so sad, i still hope this is some software issue and will be fixed i new versions.

PS. The gray field on the chart is hear rate, the blue my interval tempo. ciq.forums.garmin.com/.../1321860.png

0 Former Member over 5 years ago in reply to ASmugDill

Hi,

I just bought mine and tried it in the gym for an hour with 10 mins cardio (rowing and skiing) , core and strength work. I might as well have been asleep - my heart rate never got above 126 and most of the time it was in the 70’s. In an hour I did less than 100 calories !!!! I had high hopes after good reviews !!

0 5219736 over 5 years ago in reply to Former Member

The same with me ! Unfortunatelly my fitbit wrist band (charge 2) works so much better. That was my first trial on the cross trainer so I will see how it goes later.

Somehow fitbit managed to get much better accuracy. on wrist HR ...

0 Former Member over 4 years ago

I am a mountain biker. ive had two 735s and have a fenix5s now. in all watches, the optical HR works quite well for a few weeks/months and then becomes useless. during a hard workout where my HR is 150plus, it will report an HR closer to resting. tighness on my wrist and poaitioning do not help. with all the garmin connect drama these days i am going to switch and try another brand.

0 1083762 over 4 years ago

Gonna change to a different brand as well by bpm during exercise according to my 645 is missing usually around 70 to 100 bpm. I gotta say my 10 year old nokia watch is more accurate than this. I have tried to go over every thread about this situation and tried different fixes nothing really helps.