Datex-ohmeda, Inc.

Ohmeda Inc.

Allen Dettling

Kurt Albert Aronow

Alan D Martin

The pulse oximeter instrument of the present invention includes switched gain, channel rotation and bootstrap amplification features. In one embodiment, a time-division multiplexed gain circuit is provided in receiver circuitry and is equipped with a switched gain amplifier to faciliate the use of a fixed light source drive and otherwise improve the signal processing characteristics of the instrument. Signal processing is further enhanced via use of a transimpedance amplifier and bootstrap amplifier interconnected across one or more photodiodes. The apparatus time division multiplexes (TDM) the optical input channels to customize the gain response of the apparatus to the variable characteristics of each input channel. Thus, the channel-specific error sources are determined and precisely eliminated from the input data. The channels may also be rotated in subsequent signal conditioning that entails demultiplexing/multiplexing.

Photoplethysmographic instrument

An improved photoplethysmographic measurement system is disclosed in which a portion of a time division multiplexed (TDM) signal represents an ambient light level, and other TDM signal portions represent detected levels of two or more centered wavelengths of transmitted light. The ambient and detected light portions of the signal are simultaneously applied to the inputs of an instrumentation amplifier(s) so as to produce a continuous output voltage that is proportional to a difference in voltage between the ambient and detected light portions of a TDM signal. Such an approach provides for ambient light level subtraction with reduced noise and componentry.

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Broomfield, CO, United States of America

Allen Dettling