| 摘要 |
The invention relates to a dust indicator for detecting the presence of suspended particles, either solid or liquid, in a gas. A concentrated, substantially parallel light beam (1) of suitable wavelength is directed through a measuring chamber (2) containing the gas to be examined. The light beam is surrounded by an internally reflecting elliptical cylindrical reflector (4) in a manner such that the beam (1) coincides with one focal axis (B1) of the reflector. Arranged in the other focal axis (B2) of the reflector (4) is at least one light detector (6) with its active surface facing the reflector and the center axis of its field of view directed, preferably perpendicularly, towards the first said focal axis (B1) along which the beam (1) is directed.
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