| 摘要 |
A light emitting unit and a photo sensing unit are separately arranged to face with each other, and a pulse light is emitted from the light emitting unit at every constant period, and the photo sensing unit receives the pulse light attenuated by a smoke, thereby detecting a fire. When a power source is turned on, a microcomputer in the photo sensing unit stores the first photo sensing data as an initial photo sensing data in a memory. The initial photo sensing data is fixedly stored and held and is not erased due to a temporary cut off of the power source. The photo sensing data is converted to correction photo sensing data using a correction ratio to perform the fouling correction and the fire is discriminated on the basis of the correction photo sensing data. The correction ratio is corrected when the correction period reaches 50 minutes. A correction amount of a single correction ratio is suppressed to a microvalue. In correction of the correction ratio, it is increased or decreased by only a microvalue at every correction period until the photo sensing data coincides with the initial photo sensing data. |
