Practical and improved fire detector
AssigneeEngelhard Sensor Technologies, Inc.
InventorJacob Y. Wong
Life of this patent
Estimating the term…
Abstract
A fire detector which combines an NDIR CO.sub.2 gas detector with a photoelectric smoke detector to minimize false alarms by logic means that can be integrated into a single chip that can have an ASIC section and a microprocessor section. The NDIR CO.sub.2 detector can be single or dual channel. The NDIR CO.sub.2 gas detector and the photoelectric smoke detector can be separate or combined in a single device in which they are optically isolated by a light-tight barrier but still use a common light source. Also, the CO.sub.2 and smoke detectors can be combined on a single substrate within a common housing.
Claims20
A fire detector, comprising:
- a smoke detector;
- a non-dispersive infrared (NDIR) carbon dioxide (CO.sub.2) sensor;
- logic means for generating an alarm signal when any of the following criteria are met:
- light obscuration exceeds a threshold level for greater than a first preselected time;
- light obscuration exceeds a reduced threshold level for greater than a second preselected time;
- or
- light obscuration exceeds the reduced threshold level and the rate of increase in the concentration of CO.sub.2 exceeds a predetermined rate;
- and
- an alarm responsive to the alarm signal.
A fire detection system, comprising:
- a detector assembly, comprising:
- a case;
- a housing contained within the case;
- a substrate within the housing;
- a thermopile detector fabricated on the substrate;
- a silicon photodiode mounted on the substrate;
- a light-tight barrier that separates and optically isolates the thermopile detector from the silicon photodiode and forms a carbon dioxide detector channel and a smoke detector channel within the case;
- a light source mounted within the case;
- a carbon dioxide filter located between the light source and the thermopile detector in the carbon dioxide detector channel;
- a specularly reflective gas sample chamber formed between the light source and the thermopile detector in the carbon dioxide detector channel;
- means for circulating gas into and out of the gas sample chamber;
- and
- a smoke detector scattering chamber formed between the light source and the silicon photodiode in the smoke detector channel;
- an alarm;
- and
- a signal processor connected to the alarm and the detector assembly which contains logic means for generating an alarm signal when any of the following criteria are met:
- light obscuration exceeds a threshold level for greater than a first preselected time;
- light obscuration exceeds a reduced threshold level for greater than a second preselected time;
- or
- light obscuration exceeds the reduced threshold level and the rate of increase in the concentration of carbon dioxide (CO.sub.2) exceeds a predetermined rate;
- and
- an alarm responsive to the alarm signal.
Dependencies are inferred from the claim text.