Fire alarm system with sensitivity adjustment
First Claim
Patent Images
1. A fire alarm system comprising:
- a fire sensor providing a sensor signal for monitoring an environmental condition; and
a processor which indicates an alarm condition when the sensor signal exceeds an alarm threshold, the alarm threshold being variable by the processor to adjust sensitivity of the alarm system to the sensor signal, the processor automatically adjusting the threshold over time responsive to individual sensor signal peak values while monitoring for an alarm condition.
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Abstract
A fire alarm system automatically adjusts sensitivity of individual sensors based on evaluation of background level over a period of time. High sensor signals which do not trigger a fire alarm may, after a delay time, result in decreased sensitivity to avoid false alarms. On the other hand, low peak values stored over a period on the order of months result in an automatic increase in sensitivity of the system. The sensitivity is adjusted by changing the delta threshold of an alarm threshold over a quiescent sensor signal average.
69 Citations
41 Claims
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1. A fire alarm system comprising:
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a fire sensor providing a sensor signal for monitoring an environmental condition; and a processor which indicates an alarm condition when the sensor signal exceeds an alarm threshold, the alarm threshold being variable by the processor to adjust sensitivity of the alarm system to the sensor signal, the processor automatically adjusting the threshold over time responsive to individual sensor signal peak values while monitoring for an alarm condition. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A fire alarm system comprising:
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a fire sensor providing a sensor signal for monitoring an environmental condition; and a processor which indicates an alarm condition when the sensor signal exceeds an alarm threshold which is a delta threshold over a varying quiescent sensor signal level, the delta threshold being variable by the processor to adjust sensitivity of the alarm system to the sensor signal, the processor automatically adjusting the delta threshold over time responsive to the sensor signal while monitoring for an alarm condition.
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11. A fire alarm system comprising:
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a fire sensor providing a sensor signal for monitoring an environmental condition; and a processor which indicates an alarm condition when the sensor signal exceeds an alarm threshold which is a delta threshold over a varying quiescent sensor signal level, the delta threshold being variable by the processor to adjust sensitivity of the alarm system to the sensor signal, the processor automatically adjusting the delta threshold over time responsive to the sensor signal while monitoring for an alarm condition, the processor increasing sensitivity with low sensor signal peaks over a period of time. - View Dependent Claims (12, 13, 14)
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15. A fire alarm system comprising:
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a fire sensor providing a sensor signal for monitoring an environmental condition; and a processor which indicates an alarm condition when the sensor signal exceeds an alarm threshold, the threshold being the sum of a delta threshold and a quiescent sensor signal average, the delta threshold being incremented to decrease sensitivity a delay time after a high peak sensor signal and being decremented to increase sensitivity at the end of a period of time where a stored peak sensor signal is low during the period of time, the stored peak value being reset at the end of the delay time and at the end of the period of time.
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16. A method of detecting a fire comprising:
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converting an ambient condition to a sensor signal; electronically indicating an alarm condition when the sensor signal exceeds a threshold; and electronically varying sensitivity relative to the sensor signal by adjusting the threshold over time responsive to peak sensor signals while monitoring for an alarm condition. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24)
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25. A method of detecting a fire comprising:
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converting an ambient condition to a sensor signal; electronically indicating an alarm condition when the sensor signal exceeds an alarm threshold, the alarm threshold being a delta threshold over a varying quiescent sensor signal level; and electronically varying sensitivity relative to the sensor signal by adjusting the delta threshold over time responsive to the sensor signal while monitoring for an alarm condition.
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26. A method of detecting a fire comprising:
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converting an ambient condition to a sensor signal; electronically indicating an alarm condition when the sensor signal exceeds an alarm threshold, the alarm threshold being a delta threshold over a varying quiescent sensor signal level; electronically varying sensitivity relative to the sensor signal by adjusting the delta threshold over time responsive to the sensor signal while monitoring for an alarm condition; and electronically increasing sensitivity with low sensor signal peaks over a period of time. - View Dependent Claims (27, 28, 29)
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30. A fire alarm system comprising:
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a fire sensor providing a sensor signal for monitoring percent obscuration per foot; and a processor which indicates an alarm condition when the sensor signal exceeds an alarm threshold, the alarm threshold being the sum of a delta threshold and a quiescent sensor signal average, the processor automatically adjusting the delta threshold over time responsive to sensor signal peaks while monitoring for an alarm condition to adjust sensitivity of the alarm system to the sensor signal, delta threshold being decremented to increase sensitivity when a peak percent obscuration per foot is less than a first percentage of a threshold over a period of time and is incremented to decrease sensitivity a delay time after a peak value when the peak percent obscuration per foot exceeds a second percentage of the threshold. - View Dependent Claims (31, 32, 33, 34, 35)
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36. A method of detecting a fire comprising:
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converting an ambient condition to a sensor signal; electronically indicating an alarm condition when the sensor signal indicates percent obscuration per foot exceeding an alarm threshold, the alarm threshold being a delta threshold over a varying quiescent sensor signal level; and electronically varying sensitivity relative to the sensor signal by adjusting the delta threshold over time responsive to the sensor signal while monitoring for an alarm condition, the threshold being decremented to increase sensitivity when a peak percent obscuration per foot is less than a first percentage of a threshold over a period of time and is incremented to decrease sensitivity a delay time after a peak value when the peak percent obscuration per foot exceeds a second percentage of the threshold. - View Dependent Claims (37, 38, 39, 40, 41)
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Specification