Patent Document ID: 5448991
Application ID: 07891760
Patent Flag: 1

Claim One:
1. A method of measuring oxygen saturation in the blood of a living person, comprising the steps of: (a) generating a reference signal having a fixed level during an oxygen saturation monitoring interval; (b) during said oxygen saturation monitoring interval, generating light having a first wavelength and light having a second wavelength, said light of said first and second wavelengths each having a fixed output level proportional to said fixed level of said reference signal; (c) directing said light towards a blood carrying tissue sample; detecting the light of said first and second wavelengths, after passage through said tissue sample, and generating, in response to said light detection, a first electrical signal related to said first wavelength, and a second electrical signal related to said second wavelength, said first and second electrical signals each having a signal magnitude related to the degree of oxygen saturation in said blood and being less than an expected maximum signal magnitude and more than an expected minimum signal magnitude; (e) providing said first and second electrical signals as input to a signal conversion means having a dynamic range extending from at least said expected minimum signal magnitude to at least said expected maximum signal magnitude so that said signal conversion means accommodates said first and second electrical signals and converts said first electrical signal into a first digital signal and said second electrical signal into a second digital signal; (f) processing said first and second digital signals in computer processing means so as to compute the oxygen saturation level of said blood during said oxygen saturation monitoring interval.