On 28/06/2018 18:39, Andrew Gabriel wrote:
> In article ,
>  spuorgelgoog@gowanhill.com writes:
>> On Sunday, 24 June 2018 11:47:17 UTC+1, Andrew Gabriel  wrote:
>>> I bought a standard pulse oximeter, thinking it would be interesting
>>> to observe while I'm cycling. It wasn't ...
>>
>> I'm told they're useful devices to have for first-aiders as they're easier
to use than trying to find a pulse.
>
> They only work if you have a pulse, and it has to be regular.
> They can't work with someone who has an irregular heart beat,
> or no detectable peripheral pulse, because they have to be able
> to work out precise fractions of each pulse in order to derive
> the SpO2 level. Obviously, they can show an irregular pulse
> (if they can see one at all), but not work out the oxygen
> saturation in that case.
>

That's intriguing, for how does one calculate the O2 based on
the fraction of time that the pulse is there?

Once had to do a PID control system for dissolved oxygen, but the
glassware and probes were complex

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