| 摘要 |
<p>PURPOSE:To measure an element to be measured with higher accuracy by continuously measuring the carbon gas concentration of a sample gas and finding the oxygen gas concentration of the sample gas at every instant from the carbon gas concentration, and then, correcting the difference in sensitivity caused by the difference between base gases based on the oxygen gas concentration. CONSTITUTION:A sample gas S and reference gas R are alternately supplied to a cell 11 by switching the gases S and R to each other at fixed periods while the cell 1 is irradiated with infrared rays from an infrared light source 7. A NOx concentration detector inputs An AC signal (a) which is proportional to the NOx and H2O concentrations of the sample gas S to a subtracting circuit 12 and the circuit 12 outputs a signal c representing the NOx concentration to a subtractor 17. On the other hand, a CO2 concentration detector 13 outputs a signal (d) representing the CO2 concentration of the sample gas and a concentration conversion circuit 16 inputs the signal (d) to the subtractor 17 after converting the signal (d) into an O2 concentration signal (e). The subtractor 17 measures the NO2 concentration of the sample gas S by calculating (c-e) and canceling the influence of O2 which is the base gas of the sample gas S.</p> |
