| 摘要 |
A method and device for measuring a concentration of a preselected gas in a gas sample are disclosed. The device comprises a Herriott type multipass cell ( 10 ) having a center axle ( 74 ) and a housing ( 80 A, 80 B) surrounding and spaced from the axle to provide a tubular sample cavity ( 84 ). The gas sample is pumped through the sample cavity via apertures ( 154, 156 ) provided in opposed ends of the axle. A first mirror ( 44 ) and a second mirror ( 46 ) are supported at opposed ends of the axle. A light source, e.g. a laser or LED, is provided for emitting a light beam into the sample cavity via an entry aperture ( 30 ) in the first mirror, the light beam having a wave length at which the preselected gas strongly absorbs. The beam is reflected between the mirrors for a number of times before exiting the cell via an exit aperture ( 48 ) in the second mirror and impinging on a detector ( 52 ). The device further comprises a reference detector ( 32 ) for monitoring the intensity of the unattenuated light beam and a detector for detecting the intensity of light transmitted through the second mirror after a single pass through the cell. The light source is operatively connected to a heat control assembly having a heat sink and the gas sample is passed said heat sink to augment temperature control of the light source.
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