| 摘要 |
PURPOSE:To realize stable operation for a long period of time, in a photoelectric scattering type amoke detector, by compensating the output of scattered light photo detector with the output of direct light photo detector, and compensating the changes in the quantity of light due to deterioration of light emitting body and photo detector or contamination of the surface. CONSTITUTION:By using a shield plate 4, a light emitting body 1(=12), a direct light photo detector 2 (=13), and a scattered light photo detector 3 (=14) are properly installed in an external light shielding structure 5 to compose a photo-electric scattering type smoke detector. The output of the photo detector 13 which receives the direct light from the light emitting body 12, and the output of the photo detector 14 whcih receives the scattered light due to smoke when smoke is present in the structure 5 are inputted into an analog divider 17 by way of amplifiers 15, 16, respectively. The output of the scattered light photo detector is divided by the output of the direct light photo detector, and the quotient thereof is compared with the set reference voltage inputted from a reference voltage generator 19 in a comparator 18. If exceeding the set valve, an ON signal is issued; if not, an OFF signal is issued. |
