Pulse Oximeters - How do they work?

2. Pulse oximeters work by having a red and infrared diode emitting light with sensors opposite.
Red light is absorbed by oxygenated blood and Infrared light is absorbed by dexoygenated blood. Between them will be a finger, for example, or an ear lobe, so that the diodes emit light through the body part and the detectors calculate the relative absorption of each type of light.
The readings are taken many times per second and this is translated by a special circuit to display the results on screen.