| 摘要 |
PURPOSE:To obtain a smoke sensor generating no erroneous operation, by prohibiting the input of the light from a light emitting part to a signal processing part during the predetermined time almost equal to the required time before said light reaches a light receiving part through a reflective body. CONSTITUTION:The pulse S1 from a pulse generation part 11 is sent out as an intermittent light pulse from a light emitting element 13 and reflected from a reflective body 2 to be received by a light receiving element 14 after the required time T1 corresponding to the length of a light path. The pulse S2 from the generating part 11 is delayed by the time T1 by a delay part 15 to be inputted to a gate part 16 as a gate opening signal S3. Therefore, even if smoke is present in the light path and reflected light due to smoke is detected by the light receiving element 14, the gate part 16 is not opened during this period. As a result, the reflected light due to smoke is prevented from passing through the gate part 16 and only the reflected light from the reflective body 2 passes through the gate part 16 to be inputted to a signal processing part 18. The attenuation quantity of the reflected light of the reflective body 2 is detected in the processing part 18 and, when the attenuation quantity is a predetermined value or more, a smoke detection signal is outputted as extinction due to smoke to prevent an erroneous operation due to the reflection of smoke. |
