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  • oxygen meters

    From RichD@21:1/5 to All on Tue Feb 16 14:44:57 2021
    Anybody know anything about the innards of those fingertip
    O2 rate meters? sensor, theory of operation, silicon, etc.?

    I recently had some medical treatment, they were checking it
    3 times / day, and I'm curious -

    I don't expect chemists to be experts on the electronics,
    but maybe the chemistry -

    --
    Rich

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  • From Andy Burns@21:1/5 to RichD on Wed Feb 17 00:02:43 2021
    RichD wrote:

    Anybody know anything about the innards of those fingertip
    O2 rate meters? sensor, theory of operation


    Shine a red light and an infrared light through* a blood vessel onto an
    opto sensor.

    check the relative absorption of the two wavelengths in the blood, there
    is a correlation between oxygen saturation and their absorption ratio.




    [*] not reflected off the blood vessels like the phone versions.

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  • From dlzc@21:1/5 to Andy Burns on Wed Feb 17 05:47:55 2021
    On Tuesday, February 16, 2021 at 5:02:47 PM UTC-7, Andy Burns wrote:
    RichD wrote:

    Anybody know anything about the innards of those fingertip
    O2 rate meters? sensor, theory of operation
    Shine a red light and an infrared light through* a blood vessel onto an
    opto sensor.

    check the relative absorption of the two wavelengths in the blood, there
    is a correlation between oxygen saturation and their absorption ratio.

    And they can be fooled by CO in the blood too. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7301832/
    ... just as we can produce acid in our muscles under stress, we can produce CO as well as part of an abnormal respiration...

    David A. Smith

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  • From RonTheGuy@21:1/5 to Andy Burns on Thu Apr 1 22:22:41 2021
    On Feb 16, 2021, Andy Burns wrote
    (in article<news:[email protected]>):

    Shine a red light and an infrared light through* a blood vessel onto an
    opto sensor.

    check the relative absorption of the two wavelengths in the blood, there
    is a correlation between oxygen saturation and their absorption ratio.

    Why red?
    TIA

    Ron, the humblest guy in town.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From dlzc@21:1/5 to RonTheGuy on Sun Apr 4 07:34:58 2021
    Dear RonTheGuy:

    On Thursday, April 1, 2021 at 11:22:44 PM UTC-7, RonTheGuy wrote:
    On Feb 16, 2021, Andy Burns wrote
    Shine a red light and an infrared light through* a blood
    vessel onto an opto sensor.

    Why red?

    Most efficient.
    1) Red LEDs are very efficient and low voltage,
    2) If you put a "white light" flashlight up against the palm of your hand the only light that makes it through is red, and
    3) Red blood cells change color based on the amount of oxygen (or carbon monoxide) they contain.

    Ride the horse in the direction it is going.

    David A. Smith

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  • From =?UTF-8?B?SMOkcnJhIFJhbW9i?=@21:1/5 to All on Wed Dec 29 00:35:03 2021
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  • From Info Libera@21:1/5 to All on Wed Dec 29 10:45:56 2021
    Em sexta-feira, 2 de abril de 2021 às 03:22:44 UTC-3, RonTheGuy escreveu:
    On Feb 16, 2021, Andy Burns wrote
    (in article<news:[email protected]>):
    Shine a red light and an infrared light through* a blood vessel onto an opto sensor.

    check the relative absorption of the two wavelengths in the blood, there is a correlation between oxygen saturation and their absorption ratio.
    Why red?
    TIA

    Ron, the humblest guy in town.

    Maybe tha the red light penetrates deeper than blue light.
    The reason is that skin consists of a range of chromophores which have scattering and absorption coefficients which are highly wavelength dependent ...
    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5653719/

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