Optical HR limitations
What is the lowest heart rate this device can measure? Oura ring for example tells outright that due to technical limitations, it can’t measure lower than 33. Often I get gaps on its data and lowest value being 34, sometimes it manages to catch 33. Suunto 9 Baro seems to consistently measure a beat or two higher. I recall once it measuring a value of 32 but generally it shows my RHR being 35 or 36.
For comparison, I have used Polar OH1 some nights. It results in a realistic looking graph with multiples instances of 30, 31 and 33 but I have no idea if that is reliable data.
And what about newer hardware, are they any different in this regard?