How Does A Pulse Oximeter Work? Pulse oximeters rely on light absorption differences between oxygen-rich and oxygen-poor haemoglobin. Though the technology might sound sophisticated, the device’s small size and accessible design make it easy to use at home. Whether you’re caring for a loved one or keeping tabs on your own health, the simple act of clipping a device onto your finger can provide immediate readings whenever you need them. 1.1 The Science Behind Light Absorption