| 摘要 |
1,098,533. Detecting gases electrically. SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ N.V. Dec.19, 1966, No.56731/66. Heading G1N. In a lightweight portable hydrogen flame ionization detector for detecting leaks of hydrocarbons from gas mains or service pipes, air is continuously sampled by being sucked into a probe 20 and pumped through a minor flow-rate path 11 to a burner 3 where it is mixed with hydrogen and also through a major flow-rate path 14 to the detector chamber to provide a supporting atmosphere for the flame and to remove products of combustion from the interior of the detector. A third path 18 may lead direct to the atmosphere or through the outer casing 26 to provide a downdraught. Glass wool 28 prevents draughts entering the detector. Flowmeters and filters 12, 15 are provided in the paths 11, 14. The burner itself serves as one electrode, the other being a hollow cylinder 2 at a potential of + 100 volts. Variations in current due to the presence of hydrocarbons in the sampled air are converted into frequency variations fed to headphones 25. In a modification, Fig. 2 (not shown), the sampled air is pumped through a filter (31) and then divides between a capillary (35) leading to the burner and a wider branch (36) leading to the chamber. A visual indicator may be provided. |
