Self-adjusting smoke detector with self-diagnostic capabilities
First Claim
1. A self-contained, self-adjusting smoke detector that communicates with a central controller, comprising:
- a smoke sensing element operable to produce a sensing element signal indicative of a smoke level in a spatial region, the smoke sensing element producing a clean air reference signal that represents a clean air smoke level in the spatial region;
a discrete housing that mounts the sensing element, has openings through which smoke particles flow from the spatial region to the smoke sensing element, and has interior surfaces, the interior surfaces being susceptible to dust accumulation that causes undersensitivity of the smoke sensing element to smoke particle flow;
an autonomous, self-adjusting alarm control circuit for determining an excessive level of smoke that indicates an alarm condition, the alarm control circuit determining successive floating adjustments from the clean air reference signal and from smoke level data acquired at different data acquisition times from the sensing element signal, each successive floating adjustment being determined by comparing over a data gathering time interval differences between multiple, time displaced smoke level data acquired from the sensing element signal and the clean air reference signal and calculating an offset value corresponding to the difference determined, the data gathering time interval spanning a time that is long in comparison to the smoldering time of a slow fire in the spatial region, and each floating adjustment determined in accordance with the offset value offsetting corresponding current smoke level data to produce adjusted smoke level data, the adjusted smoke level data being compared against an alarm threshold to develop an alarm signal representative of the existence of an alarm condition when the alarm threshold is exceeded; and
a signal transmitter operatively associated with the central controller and the alarm control circuit for self-initiated transmission of the alarm signal to the central controller to signal the existence of an alarm condition.
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Accused Products
Abstract
A smoke detector (10) has internal self-adjustment and self-diagnostic capabilities. It includes a microprocessor-based alarm control circuit (24) that periodically checks the sensitivity of a smoke sensing element (20) to a smoke level in a spatial region (12). The alarm control circuit and the smoke sensor are mounted in a discrete housing (25) that operatively couples the smoke sensor to the region. The microprocessor (30) implements a routine (50) stored in memory (32) by periodically determining a floating adjustment (FLT-- ADJ) that is used to adjust the output (RAW-- DATA) of the smoke sensing element and of any sensor electronics (40) to produce an adjusted output (ADJ-- DATA) for comparison with an alarm threshold. The floating adjustment is not greater than a maximum value (ADJISENS) or less than a minimum value (ADJSENS). Except at power-up or reset, each floating adjustment is within a predetermined slew limit of the immediately preceding floating adjustment. The floating adjustment is updated with the use of averages (NEW-- AVG) of selected signal samples taken during data gathering time intervals having a data gathering duration that is long in comparison to the smoldering time of a slow fire. The adjusted output is also used for self-diagnosis.
217 Citations
20 Claims
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1. A self-contained, self-adjusting smoke detector that communicates with a central controller, comprising:
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a smoke sensing element operable to produce a sensing element signal indicative of a smoke level in a spatial region, the smoke sensing element producing a clean air reference signal that represents a clean air smoke level in the spatial region; a discrete housing that mounts the sensing element, has openings through which smoke particles flow from the spatial region to the smoke sensing element, and has interior surfaces, the interior surfaces being susceptible to dust accumulation that causes undersensitivity of the smoke sensing element to smoke particle flow; an autonomous, self-adjusting alarm control circuit for determining an excessive level of smoke that indicates an alarm condition, the alarm control circuit determining successive floating adjustments from the clean air reference signal and from smoke level data acquired at different data acquisition times from the sensing element signal, each successive floating adjustment being determined by comparing over a data gathering time interval differences between multiple, time displaced smoke level data acquired from the sensing element signal and the clean air reference signal and calculating an offset value corresponding to the difference determined, the data gathering time interval spanning a time that is long in comparison to the smoldering time of a slow fire in the spatial region, and each floating adjustment determined in accordance with the offset value offsetting corresponding current smoke level data to produce adjusted smoke level data, the adjusted smoke level data being compared against an alarm threshold to develop an alarm signal representative of the existence of an alarm condition when the alarm threshold is exceeded; and a signal transmitter operatively associated with the central controller and the alarm control circuit for self-initiated transmission of the alarm signal to the central controller to signal the existence of an alarm condition. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. In a smoke detector including a smoke sensing element that produces a sensing element signal indicative of a smoke level in a spatial region and including a canopy having openings through which smoke particles flow and having interior surfaces that are susceptible to dust accumulation, a method of making the smoke detector operationally compatible with a replacement canopy having different operational characteristics stemming from dust accumulated on and differences in the properties of its interior surfaces, comprising:
providing a self-adjusting alarm control circuit for determining whether there exists in the spatial region an excessive level of smoke that indicates an alarm condition, the alarm control circuit determining successive floating adjustments from a clean air reference signal and from smoke level data acquired at different data acquisition times from the sensing element signal, each successive floating adjustment being determined by comparing over a data gathering time interval differences between multiple, time displaced smoke level data acquired from the sensing element signal and the clean air reference signal and calculating an offset value corresponding to the difference determined, the data gathering time interval spanning a time that is long in comparison to the smoldering time of a slow fire in the spatial region, and each floating adjustment determined in accordance with the offset value offsetting corresponding current smoke level data to produce adjusted smoke level data, the adjusted smoke level data being compared against an alarm threshold to develop an alarm signal representative of the existence of an alarm condition when the alarm threshold is exceeded. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. A self-contained, self-adjusting smoke detector that communicates with a central controller and has self-diagnostic capabilities, comprising:
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a smoke sensing element operable to produce a sensing element signal indicative of a smoke level in a spatial region, the smoke sensing element producing a clean air reference signal that represents a clean air smoke level in the spatial region; and a processor receiving and processing the sensing element signal, the processor determining successive floating adjustments from the clean air reference signal and from smoke level data acquired at different data acquisition times from the sensing element signal, each successive floating adjustment being determined by comparing over a data gathering time interval differences between multiple, time displaced smoke level data acquired from the sensing element signal and the clean air reference signal and calculating an offset value corresponding to the difference determined, and each floating adjustment determined in accordance with the offset value offsetting corresponding current smoke level data to produce adjusted smoke level data;
the processor comparing the adjusted smoke level data to multiple threshold values, one of the threshold values representing a smoke obscuration alarm level and another of the threshold values representing a tolerance limit for the smoke sensing element; and
the processor determining from the adjusted smoke level data corresponding to smoke obscuration levels that exceed the alarm level and from adjusted smoke level data corresponding to smoke observation levels that exceed the tolerance limit whether the adjusted smoke level data are indicative of an alarm condition or an out-of-calibration condition of the system. - View Dependent Claims (18, 19, 20)
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Specification