| 摘要 |
A device as described whereby the concentration of a gas such as alcohol vapor can be measured using radiation absorption techniques in a chamber. The chamber is an elongated tube having a window at one end through which infra red radiation can pass with an optical reflector at the two ends of the tube and at least one other reflector for causing the reflected radiation to leave the tube through a second window in the side of the tube, from where it passes to a detector.
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