ISOTOPIC GAS MEASURING INSTRUMENT

摘要

PROBLEM TO BE SOLVED: To provide an isotopic gas measuring instrument capable of repeatedly and stably measuring the concentration of an isotopic gas with little influence of interference of 12CO2 in the absorbance measurement of 13CO2. SOLUTION: The light from an infrared light source 1 is absorbed by 12CO2 gas and 13CO2 gas contained in a sample gas of cells 3 and 4 and thereafter measured by infrared detectors 11 and 12. Although the cell 4 on the 12CO2 side and the cell 3 on the 13CO2 side are respectively influenced by the interference of the other-side gas, the interference of the 13CO2 can be neglected in the output obtained from the infrared detector 12 because the presence rate of the 13CO2 gas is around 1.1% in the cell 4 and due to the optical characteristic of an interference filter 9. In the cell 3, the influence of the interference of the 12CO2 on the output obtained from the infrared detector 11 can be reduced by the 12CO2 gas filled in a gas cell 6 installed after the cell 3 and by the optical characteristic of an interference filter 8.