Patent Number: 039873030
Section: abstract

A gas analyzer is provided which is particularly suited for making transcutaneous measurement of the CO.sub.2 concentration in the blood.. In accordance with one embodiment of the invention, sample gases from the body are circulated in a cavity of the device. A rotating wheel in the cavity includes two reference cells and a sample cell which are sequentially rotated into the optical path between a source and a detector. Three signals are thereby provided which may be combined to give an output indication of the CO.sub.2 concentration in the body fluids. In a preferred embodiment, the sample cell is an "inverted cell" being in open communication with the sample gas circulating in the device so that the gas in the sample cell is a portion of the circulating gas which also surrounds the two reference cells. An output indication is thereby obtained which is insensitive to contaminants in the sample.. In accordance with another embodiment, the sample cell is isolated from the region surrounding the wheel and positioned so as to be presented in series with the reference cells in the optical detection path.. In preferred embodiments, the rotating wheel contains a number of permanent magnets which interact with a number of electromagnets driven in sequence to provide rotation of the wheel.