| 摘要 |
Fluid, such as air, flowing through a duct is sampled by a detector in a chamber by withdrawing a portion of the fluid from the duct by an impact tube which connects the duct to an inlet in the sampling chamber. Several openings in the impact tube extend across the duct and face into the direction of fluid flow in order to obtain a cross-sectional and representative sample of the fluid. To insure that an adequate sample is obtained, one or more venturi tubes are also placed into the direction of the flow path of the fluid and these venturi tubes are connected to the outlet of the sampling chamber to exert a pressure in the chamber which is negative with respect to the chamber inlet from the impact tube.
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