Light Plethysmograph

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Light Plethysmograph measures the reflection from or transmission through a capillary bed like the fingertip or ear lobe. It can provide a signal that indicates pulsatile changes of the volume of blood in the capillary bed. This technique consists of a light source and photodetector and can be used to observe heart beat rate or cardiac cycles.



  • Transmittance sensor probe to fit on fingertip
  • Sensor consists of Red LED and matching Photodiode
  • System includes breadboard and components
  • Need external power supply [5V]
  • Output signal can be observed using oscilloscope or DAQ system
  • The user manual describes the mechanism of this technique with circuit diagrams.

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