| 摘要 |
PURPOSE:To prevent adhesion of suspended matter and deterioration of measuring accuracy, by allowing a fluid body to flow on front surfaces of a light projector and a light receiver, which are brought in contact with a fluid body containing suspended matter. CONSTITUTION:Smoke from a combustion furnace 1 is diffused in a measuring chamber 3 by an exhausting device 2, light from a light projector 4 is received by a light receiver 5, and measurement of smoke is conducted by comparing presmoke- exhaustion light-receiving amount with post-smoke-exhaustion light-receiving amount. Front surfaces of the light projector 4 and the light receiver 5 are provided with blow holes 41 and 51 so as to allow air to blow out appropriately to keep smoke density distribution constant and to prevent the smoke from contacting a light-projecting lens 42 and a light-collecting lens 52. The air is guided from an introducing inlet 44 to an air chamber 45, made to pass through a communicating hole 49, heated by a heater 48' and blown off to front surface of the light-projecting lens 42 from the blow hole 41. By raising temperature of air, it is possible to prevent smoke from being cooled off and also to provide better prevention of adhesion of particles contained in the smoke. |
