Measuring principle of pulse blood oxygen meter.
Based on the change of light absorption during arterial pulsation. Each of the two light sources located in the visible red spectrum (660 nm) and the infrared spectrum (940 nm) alternately irradiated the tested area (usually the fingertip or earlobe). The amount of light absorbed during these pulses is related to the oxygen content in the blood.
The microprocessor calculates the ratio of the two spectra absorbed and compares the results with the saturation value table in the existing memory to obtain the oxygen saturation of blood. A typical blood oxygen sensor has a pair of LEDs that are facing a photodiode through the translucent part of the patient's body (usually the fingertip or earlobe). One of the LEDs is red, the wavelength is 660nm, the other is infrared, and the wavelength is 940nm. The percentage of blood oxygen is calculated by measuring the light passing through the body of the two wavelengths with different absorption rates.