On Thu, 28 Jun 2018 19:08:47 +0100, Gareth's Downstairs Computer
 declaimed the following:

>
>That's intriguing, for how does one calculate the O2 based on
>the fraction of time that the pulse is there?
>
 I don't think it's the fraction of time that the pulse is present so
much as being able to sample two pulses in a row at the detected pulse rate
-- in order to compare the detected light transmission at the two different
wavelengths...

 When I Googled the devices I seem to recall something that mentioned
light transmission in deep (visible) red vs transmission of infra-red.
Those measurements are done sequentially (the sensors can't quite
differentiate the light source so it needs vr/pause/ir/pause... and slow
detectors may require timing to catch the peak of the pulse for each).


--
 Wulfraed                 Dennis Lee Bieber         AF6VN
 wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/

--- SoupGate-Win32 v1.05