| 摘要 |
PROBLEM TO BE SOLVED: To prevent the occurrence of error alarm due to moisture condensation in a fire alarm. SOLUTION: A measurement means is composed of a microcomputer 11, a sample and hold circuit 13 and an A/D conversion circuit 14, and a smoke sensor 12 acquires a measurement value. Under the control of the microcomputer 11, smoke is measured in a smoke detecting sampling period of a four-second interval in a monitoring mode. When the measurement value exceeds only a first threshold (10%/m), a smoke judgment count is increased by "1". Sudden rise of a measurement value of the smoke sensor 12 due to irregular reflection on water drops caused by dew condensation is detected. When the measurement value exceeds a second threshold (20%/m) at first from a value less than the first threshold (safety range), the counting processing of the smoke judgment count is canceled and fire alarm processing is controlled to cancel an alarm mode. The number of cancels is counted, and when the number of cancels becomes a prescribed number of times, the counting processing of the smoke judgment count is restarted and the monitoring mode can be shifted to the alarm mode by delaying shift time only by the number of cancels. COPYRIGHT: (C)2009,JPO&INPIT
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