| abstract |
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 or 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. |