Which software are you using? I don't think it's reliable yet with either InfiniTime 1.3 or with Wasp-OS. The former is from practical experience - it's not too bad IF you both get the strap tension just right, and keep your wrist still. I get the impression it's similar with Wasp-OS from one of the other threads , but haven't tried it. It does have the option of recording the raw sensor data and downloading it so someone sufficiently motivated can improve on the relatively simplistic algorithm.
https://wasp-os.readthedocs.io/en/latest...te-monitor
https://forum.pine64.org/showthread.php?...3#pid99003
https://wasp-os.readthedocs.io/en/latest...te-monitor
https://forum.pine64.org/showthread.php?...3#pid99003
