I purchased an FR 255 few days back. I am very happy with the accuracy of swimming data and calorie measurements. It has been a great and polished experience in that sense.
I struggle however with the heart rate measurements when not exercising.
My RHR in the morning measured by both pulseoximeter and a manual pulse reading is in the 40-49 range. The watch does measure in this range, but it fluctuates sending readings into their 70s for ten seconds or more, and then returning back. I tracked this in parallel with a medical pulseoximeter as well as manually and found that the fluctuations are inaccurate.
Adjusting the strap did not do much. What worked however was a deep breathing exercise. While keeping the brm roughly the same, with the exercise the fluctuations were minimal.
The first pic attached above was with the exercise. And second one below was done with my regular breathing pattern.
In the second image you can see the sort of peak which has gone into higher 60s. Sometimes it goes even into higher 70s and more often, totally skewing the data.
So my question is: While I can still do accurate health snapshots or RHR measurements by relaxing with deep breathing, I cannot really make good use of sleep, body battery and other functions. Yesterday the watch simply did not detect my sleep. I checked the heart rate graph and found it had readings full of 70 bpm spikes, which I assume were wrong, because I had a good 7 hour sleep. Is there any way I can solve this? I have tried putting the strap as mentioned by Garmin, cleaned the sensor, etc.