[HN Gopher] How pulse oximeters work explained
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       How pulse oximeters work explained
        
       Author : jacquesm
       Score  : 8 points
       Date   : 2022-05-30 19:50 UTC (3 hours ago)
        
 (HTM) web link (www.howequipmentworks.com)
 (TXT) w3m dump (www.howequipmentworks.com)
        
       | exmadscientist wrote:
       | Pretty nice explanation!
       | 
       | Commercial pulse oximeters don't always do things exactly this
       | way, but that's more a matter of "secret sauce" than anything
       | else. The principles here are all you really need to understand a
       | basic pulse oximeter. There are more advanced techniques, like
       | Masimo's Rainbow SET, but it's just the same idea with more LEDs.
       | 
       | More interesting to people around here is what the hardware
       | connects to. These things are typically used with patient
       | monitors, those things that display the little charts and go
       | "beep" when your heart beats. Most sensors that connect to a
       | patient monitor are read out by the monitor itself, so a Nihon
       | Kohden and a Mindray monitor might have slightly different
       | sensitivities. It's all handled by manufacturer-designed hardware
       | and manufacturer-controlled software. Not so for SpO2. SpO2 is
       | actually handled by a _complete board with firmware_ purchased
       | from one of the major sensor vendors (usually Nellcor or Masimo).
       | And this board has actual moderately-good security locking down
       | its firmware, and in some cases uses obscure hardware to make it
       | even harder to reverse engineer. Kind of wild!
        
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       (page generated 2022-05-30 23:01 UTC)