| 摘要 |
PROBLEM TO BE SOLVED: To prevent false alarm due to water vapor in a fire alarm. SOLUTION: A measuring means comprises a microcomputer 11, a sample-and-hold circuit 13 and an A/D conversion circuit 14, and a measurement value is acquired by a smoke sensor 12. By control of the microcomputer 11, in a monitor mode, the value is measured as a sampling cycle for smoke detection every four seconds interval. When the measured value exceeds a threshold, a smoke judgment count is increased by 1. In the sampling cycle to be at 250 m seconds intervals which are shorter than one for smoke detection, measurement is performed 16 times, for example. When there are cases in which the measured value becomes equal to the threshold or smaller or a difference between a maximum measured value and a minimum measured value becomes the threshold or larger, the smoke judgment count is decreased by 1. When neither of the cases exists, the smoke judgment count is increased by 1. Measurement at 25 0m seconds intervals and the judgment are repeated. When the smoke judgment count becomes 3, an alarm mode is set in. When the smoke judgment count becomes 0, the alarm mode is not set in but the monitor mode in which measurement is performed at every 4 seconds interval is resumed. COPYRIGHT: (C)2009,JPO&INPIT
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