| 摘要 |
PURPOSE: To make it possible to prevent the direction soot deposition in the active elements of a transmitter and receiver by providing a light transmission object. CONSTITUTION: A light having predetermined luminous intensity is emitted from a light source 43. The light beam arrives at the end forming member 38 of an optical waveguide 39, crosses the exhaust gas via a light transmission opening 16, and incident to a reflecting surface 46 via a light transmission opening 17. Then, the beam is reflected and returned to the member 38 in the opposite direction, and arrives from there at a photodetector 44 via an optical waveguide 40. After it is passed twice through the gas, the beam is detected by a detector 44 to obtain the luminous intensityϕ0 in the pure gas or the luminous intensityϕin the presence of the mixture of soot concentration. In this case, the mixture degree is compared with the limit value depending upon the number of revolutions, and the actual value deviation can be compensated by deviating the regulating rod of the pump. The optical system is protected against the dirt by heating the objects 29, 30, and hence the erroneous measured values are not obtained.
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