The finger tip pulse oximeter contains a dual light source and photo detectors. Typically it uses two LEDs (light-emitting diodes) generating red and infrared lights through a translucent part of the body. Bone, tissure, pigmentation, and venous vessels normally absorb a constant amount of light over time. Oxyhemoglobin and its deoxygenated form have significantly different absorption pattern. The arteriolar bed normally pulsates and absorbs variable amounts of light during systole and diastole, as blood volume increases and decreases. The ratio of light absorbed at systole and diastole is translated into an oxygen saturation measurement.

For the pulse oximeter to function properly, both light sources and photo detectors must be cleaned regularly. The red LED is visible and can be found easily; however the infrared LED is not visible and it is normally located right next to the red LED. They can be cleaned using soft, clean and dry cloth to avoid damages to them. Never use any water or liquid to clean the LEDs and sensors. For the shell, you can use a slightly damp soft clean cloth. Be gentle as a pulse oximeter is a delicate instrument.