An
oversampling pulse oximeter includes an
analog to digital converter with a sampling rate sufficient to take multiple samples per source cycle. In one embodiment, a pulse oximeter (100) includes two more more light sources (102) driven by
light source drives (104) in response to drive signals from a
digital signal processing unit (116). The source drives (104) may drive the sources (102) to produce a frequency division
multiplex signal. The optical signals transmitted by the light sources (102) are transmitted through a patient's
appendage (103) and impinge on a
detector (106). The
detector (106) provides an analog current
signal representative of the received optical signals. An
amplifier circuit (110) converts the analog current
signal to an analog
voltage signal in addition to performing a number of other functions. The
amplifier circuit (110) outputs an analog
voltage signal which is representative of the optical signals from the sources (102). This analog
voltage signal is received by a fast A / D converter (112) which samples the analog voltage signal to generate a digital voltage signal which can be processed by the
digital signal processing unit (116). The fast A / D converter (112) operates at a rate sufficient to take multiple samples per source cycle and may have a sampling frequency, for example, of over 41 kHz. The
digital signal processing unit (116) implements
software for averaging the samples over a source cycle for improved measurement consistency, improved
signal to noise ratio and reduced A / D converter
word length.