Apparatus for determining the .sup.13 CO.sub.2 /.sup.12 CO.sub.2 ratio of concentrations in a gas sample
AssigneeMIC Medical Instrument Corporation
InventorJoachim Gross
Life of this patent
Estimating the term…
Abstract
A measuring apparatus based on the NDIR process. Pulsed infrared light traverses in two parallel optical beams (3, 4) initially a cell (6) filled with .sup.13 CO.sub.2 and a cell (7) filled with .sup.12 CO.sub.2 and then, in parallel, two cells (8, 9) which are filled with the gas sample to be analyzed. Cells (8, 9) together with a capacitor microphone (15) serving as the pressure converting means form an optopneumatic receiver (17). By regulating the pressure in cell (6) the minimum of the pressure conversion signal is investigated and related to a correspondingly obtained reference value. The simply constructed apparatus permits a .sup.13 CO.sub.2 breathing test to be performed inexpensively.
Claims20
Apparatus for the determination of the .sup.12 CO.sub.2 /.sup.13 CO.sub.2 -ratio in a gas sample, comprising:
- an infrared light source and means to pulse said source at a frequency, two first cells traversed in parallel by the light from said light source one containing substantially only .sup.13 CO.sub.2 and the other containing substantially only .sup.12 CO.sub.2 ;
- two second cells also traversed in parallel by the light of the infrared light source and in each case containing one part of the gas sample;
- first pressure converting means having a diaphragm for converting periodic pressure fluctuations caused by the absorption of said light in two of said cells into electrical signals;
- wherein said two first cells are located in the optical path upstream of said two second cells, the pressure in one of said two first cells is adjustable and the diaphragm of said first pressure converting means is positioned in such a way that it is sensitive to pressure fluctuations in each of said two second cells.
Apparatus according to claim to 10, wherein the two third cells communicate with one another by means of a connecting line and the length of said connecting line and the frequency of the means to pulse the infrared light source are chosen in such a way that, with respect to the periodic pressure fluctuation in the two third cells, an antinode of longitudinal wave occurs at the diaphragm of the second pressure converting means.
Dependencies are inferred from the claim text.