Why Pulse Oximeter sp02 works at night only from 00 - 04 h

You have not told us if this is every day or just a one off?

YES every day the same problem

For me the start/end times are different, but the duration similar, normally around 2am-6am - I assumed this was to give you a representative sample from then you're likely to be fully asleep without draining the battery by running for a full 8 hours+

I believe it's taking readings for a 4 hr period based on on your set sleep times.  Mine also samples between midnight and 4 AM daily. 

It seems you set your sleep times from 00-04 and set SP02 readings that its only measured at night. If you want to have a broader window, either extend your sleep times or enable full time tracking.

Mine is recording all night, but then I do have mine set to record day and night so maybe that is the difference.

Hi,

in my case Sleep Time is set to 23:00-07:00, PulseOX is set to During Sleep only and it measures for me from 01:00 till 05:00 everyday: