This application report discusses the design of non-invasive optical plethysmography
also called as pulsoximeter using the MSP430FG437 Microcontroller (MCU). The
pulsoximeter consists of a peripheral probe combined with the MCU displaying the
oxygen saturation and pulse rate on a LCD glass. The same sensor is used for both
heart-rate detection and pulsoximetering in this application. The probe is placed on a
peripheral point of the body such as a finger tip, ear lobe or the nose. The probe
includes two light emitting diodes (LEDs), one in the visible red spectrum (660nm) and
the other in the infrared spectrum (940nm). The percentage of oxygen in the body is
worked by measuring the intensity from each frequency of light after it transmits
through the body and then calculating the ratio between these two intensities.