| 摘要 |
Infrared radiation from a laser is directed in part or intermittently through a sample containing a low concentration gas in a host gas. The other part or the interspersed radiation by-passes the sample. Emitted and transmitted radiation is separately detected and the ratio is formed representing relative transmission. The frequency of the laser is varied so that different frequencies but within the same absorbtion band of the gas to be detected are used. The relative transmissions for different frequencies are used to calculate electrically the concentration of the gas. |
