Condensed oximeter system with noise reduction software

An apparatus for measuring a parameter of the blood, comprising:

• at least two emitting means for emitting first and second wavelengths of electromagnetic energy through a sample;
• means responsive to the emitting means for detecting the first and second wavelengths of electromagnetic energy through the sample, the detection means producing first and second analog signals, each of said first and second analog signals having an AC and a DC component, the first analog signal corresponding to the first wavelength of electromagnetic energy and the second analog signal corresponding to the second wavelength of electromagnetic energy;
• means for separating the AC component of the first analog signal from the first analog signal to produce a first separated AC component and separating the AC component of the second analog signal from the second analog signal to produce a second separated AC component, wherein the means for separating includes a subtractor circuit;
• an analog to digital converter coupled to the means for separating, the analog to digital converter converting the first separated AC component into a first digital signal and the second separated AC component into a second digital signal, the analog to digital converter having an input voltage range;
• and
• means for taking a linear regression of a ratio of derivatives of the first and second separated AC components for a plurality of sample points in a period, the means for taking a linear regression including a microprocessor which computes the parameter of blood from the first and second digital signals, wherein the value of the parameter of blood corresponds to the derivative of the first separated AC component and the derivative of the second separated AC component.