| 摘要 |
A gas analyser employs a photoacoustic cell through which exhaust gases past. A plurality of modulated infra-red beams are incident on the cell, each at a frequency corresponding to an absorption band of a gas whose concentration is to be sensed. Each beam generates an acoustic signal at it's modulation frequency and the amplitude of the acoustic signal is used to calculate the concentration of the gas which absorbs that beam. <IMAGE> |
