| 摘要 |
PURPOSE:To simplify the circuit and to reduce the cost by providing a light emitting element which emits light intermittently and a photodetecting element which photodetects its scattered light and converts it into an electric signal, and obtaining a pulse-width coverted signal having pulse width corresponding to smoke density. CONSTITUTION:The light emitting element 1 is supplied with a pulse voltage from a pulse power source to emit light intermittently. The photodetecting element 2, on the other hand, photodetects scattered light of the light emitted by the light emitting element to a smoke detection area formed in the smoke detector and converts it into an electric signal corresponding to its smoke density to flow a photodetection current. This photodetection current is converted by a load resistance R1 into a voltage signal, which is inputted to a differentiating circuit. Further, the output of the differentiating circuit is inputted to a comparator circuit 3 to obtain the pulse-width converted signal with pulse width corresponding to the smoke density. Consequently, the circuit constitution is simplified extremely and high-precision, stable operation is obtained.
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