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Re: optoelectronics questions

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    You seem to be confused. A heart rate monitor usually monitors the heart directly (i.e. an AED); LEDs and photodiodes are used in a piece of medical equipment
    Message 1 of 3 , Nov 19, 2004
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      You seem to be confused. A heart rate monitor usually monitors the
      heart directly (i.e. an AED); LEDs and photodiodes are used in a
      piece of medical equipment called a pulse oximeter which measures
      oxygen saturation and pulse rate in the peripheral circulation. These
      devices are already widely available and used by most paramedics. A
      sensing probe clips onto the finger, toe or earlobe (in the case of
      animals, the tongue is often used).

      Use an IR emitter, the hemoglobin in the bloodstream is what absorbs
      the light and its strongest absorbption is in the near IR. Use a
      phototransistor for pickup; you can vary the base current on the
      transistor to tweak the sensitivity. You can purchase finger probes
      already made from most of the manufacturers of these units (go to
      Google and use the keywords "pulse oximeter")

      Regards
      xxxtoytech

      --- In home_electronics@yahoogroups.com, "Fahad Salem" <ee_tool@h...>
      wrote:
      >
      >
      >
      > Hello all,
      >
      > Can somebody please tell what type of emitting diode would be more
      > effeciently used to detect bio-signals as used in heart rate
      monitors. Is it
      > better to use an infra-red or just a simple red LED for this
      purpose.
      >
      > Also, is it better to use a phototransistor to collect the signal
      or just a
      > photo-sensor (resistance) or what about a diode. This project is
      meant to
      > assist paramedics and make their job easier, any feedback is
      welcomed.
      >
      > Thank you in advance
      >
      > _________________________________________________________________
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