Patent ID: 8874181

Claim:
A method for operating a pulse oximetry system, comprising: alternately generating light with a sensor at two wavelengths using a modulation frequency that is a predetermined distance from a common multiple of 50, 60, 100, and 120, where the predetermined distance is greater than a highest pulse rate of a person and lower than a distance of any harmonic of 50, 60, 100, or 120; receiving an analog sensor signal from the sensor that corresponds to received light; amplifying the analog sensor signal to provide an amplified analog sensor signal; modulating the amplified analog sensor signal with a sigma-delta modulator to provide a modulated signal; converting the modulated signal into a digital signal with a multiple bit analog-to-digital converter; decimating the digital signal with a decimator to provide a decimated signal; filtering the decimated signal with a digital filter to provide a filtered signal; and preloading the decimator and digital filter with an estimate of a settled output value.