US5079422A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Fire detection system using spatially cooperative multi-sensor input technique
Assignee: GE Identicard Systems Inc
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Filing: 1990-09-13
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Granted: 1992-01-07
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Expires: 2010-09-13
Abstract
Abstract A system for detecting fires uses at least two carbon dioxide sensors positioned at spaced locations in a room. Each sensor produces an electrical output signal representative of the carbon dioxide concentration in its vicinity. A computer calculates the ratio of the concentration sensed by each sensor to the concentration sensed by each of the other sensors, and any imbalance in the distribution of carbon dioxide will be reflected in these ratios. Random variations prevent the ratios from being equal, and the magnitude of the random variations is quantized by calculating the standard deviation of the ratios. The ratios are then normalized and compared to a threshold level that corresponds to a chosen false alarm rate.
Inventors
- 👤 Jacob Y. Wong
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 16:12
CPC Classifications
G; G08; G08B; G08B17/00; G08B17/10; G08B17/117; G01; G01N; G01N21/00; G01N21/17; G01N21/25; G01N21/255; G01N21/31; G01N21/35; G01N21/3504; G08B29/00; G08B29/18; G08B29/20; G01J; G01J1/00; G01J1/10; G01J1/16; G01J2001/161; G01J1/18; G01J2001/182; G01N21/314; G01N2201/00; G01N2201/02; G01N2201/022; G01N2201/0228; G01N2201/06; G01N2201/061; G01N2201/06186; G01N2201/069; G01N2201/0696
Claims Analysis
Total Claims: 25
Claim 1
Independent Claim
147 words
Apparatus for detecting a fire in a room, comprising in combination: at least two carbon dioxide sensors positioned at spaced locations in the room, each sensor producing an electrical output signal that represents the concentration of carbon dioxide sensed at the location of the sensor; ratio means electrically connected to said at least two carbon dioxide sensors for receiving the electrical output signals and for calculating the ratio of the concentration sensed by each sensor to the concentration sensed by each of the other sensors; normalization means responsive to the calculated ratios for producing normalized ratios; comparison means for comparing the normalized ratios to a threshold level that in the absence of a fire has only a pre-selected small probability of being exceeded by a normalized ratio; and, alarm signal generator means for generating an alarm signal when any of the normalized ratios exceeds the threshold level.
Claim 2
Dependent Claim
147 words
Apparatus for detecting a fire in a room, comprising in combination: at least two carbon dioxide sensors positioned at spaced locations in the room, each sensor producing an electrical output signal that represents the concentration of carbon dioxide sensed at the location of the sensor; ratio means electrically connected to said at least two carbon dioxide sensors for receiving the electrical output signals and for calculating the ratio of the concentration sensed by each sensor to the concentration sensed by each of the other sensors; normalization means responsive to the calculated ratios for producing normalized ratios; comparison means for comparing the normalized ratios to a threshold level that in the absence of a fire has only a pre-selected small probability of being exceeded by a normalized ratio; and, alarm signal generator means for generating an alarm signal when any of the normalized ratios exceeds the threshold level.
Claim 3
Dependent Claim
23 words
The apparatus of claim 1 wherein some of said at least two carbon dioxide sensors are positioned at different elevations within the room.
Claim 4
Dependent Claim
25 words
The apparatus of claim 1 wherein said normalization means further include means for calculating the standard deviator of the calculated ratios for a particular time.
Claim 5
Dependent Claim
26 words
The apparatus of claim 1 wherein said normalization means further include means for calculating the standard deviation of successive values of one of the calculated ratios.
Claim 6
Dependent Claim
46 words
The apparatus of claim 1 further comprising in combination inhibiting means connected to said alarm signal generator means for preventing transmission of said alarm signal if the denominator of one of the ratios is decreasing, thereby causing the corresponding normalized ratio to exceed the threshold level.
Claim 7
Dependent Claim
64 words
The apparatus of claim 1 further comprising in combination: a sensor for detecting a variable other than carbon dioxide concentration and for producing an auxiliary electrical signal representative of the variable; and, inhibiting means connected to said alarm signal generator means and responsive to said auxiliary electrical signal for inhibiting transmission of said alarm signal when said auxiliary electrical signal has a certain value.
Claim 8
Dependent Claim
15 words
The apparatus of claim 6 wherein said variable other than carbon dioxide concentration is temperature.
Claim 9
Dependent Claim
20 words
The apparatus of claim 1 wherein said normalization means further comprise memory means for storing ratios calculated at past times.
Claim 10
Dependent Claim
24 words
The apparatus of claim 8 wherein said comparison means further comprise means for comparing current ratios with the stored ratios calculated at past times.
Claim 11
Independent Claim
125 words
A method for detecting a fire in a room comprising the steps of: a) placing carbon dioxide sensors at spaced locations in the room, each of said sensors producing an electrical output signal representative of the concentration of carbon dioxide sensed in the air at its location; b) transmitting the electrical output signals generated by the sensors to a computer; c) calculating the ratio of the concentration sensed by each sensor to the concentration sensed by each of the other sensors; d) normalizing the calculated ratios; e) comparing each of the normalized ratios to a threshold level that is related in a known way to a desired false alarm rate; f) generating an alarm signal when any of the normalized ratios exceeds its threshold level.
Claim 12
Independent Claim
125 words
A method for detecting a fire in a room comprising the steps of: a) placing carbon dioxide sensors at spaced locations in the room, each of said sensors producing an electrical output signal representative of the concentration of carbon dioxide sensed in the air at its location; b) transmitting the electrical output signals generated by the sensors to a computer; c) calculating the ratio of the concentration sensed by each sensor to the concentration sensed by each of the other sensors; d) normalizing the calculated ratios; e) comparing each of the normalized ratios to a threshold level that is related in a known way to a desired false alarm rate; f) generating an alarm signal when any of the normalized ratios exceeds its threshold level.
Claim 13
Dependent Claim
27 words
The method of claim 10 wherein step a) further includes placing some of the carbon dioxide sensors at a different elevation from the other carbon dioxide sensors.
Claim 14
Dependent Claim
42 words
The method of claim 11 wherein step a) further includes placing some of the carbon dioxide sensors at a location near the ceiling of the room and others of the carbon dioxide sensors at a location near the floor of the room.
Claim 15
Dependent Claim
36 words
The method of claim 10 further comprising the additional step of inhibiting the alarm signal if the denominator of one of the ratios is decreasing, thereby causing the corresponding normalized ratio to exceed the threshold level.
Claim 16
Dependent Claim
30 words
The method of claim 10 further comprising the additional step of inhibiting the alarm signal in response to a signal from a sensor that is not a carbon dioxide sensor.
Claim 17
Dependent Claim
119 words
Apparatus for detecting a fire in a room, comprising in combination: at least two carbon dioxide sensors positioned at spaced locations in the room, each sensor producing an electrical output signal that represents the concentration of carbon dioxide sensed at the location of the sensor; normalization means electrically connected to said at least two carbon dioxide sensors for receiving the electrical output signals and for calculating normalized concentrations; comparison means for comparing the normalized concentrations to a threshold value that, in the absence of a fire, has only a pre-selected small probability of being exceeded by a normalized concentration; and, alarm signal generator means for generating an alarm signal when any of the normalized concentrations exceeds the threshold value.
Claim 18
Dependent Claim
119 words
Apparatus for detecting a fire in a room, comprising in combination: at least two carbon dioxide sensors positioned at spaced locations in the room, each sensor producing an electrical output signal that represents the concentration of carbon dioxide sensed at the location of the sensor; normalization means electrically connected to said at least two carbon dioxide sensors for receiving the electrical output signals and for calculating normalized concentrations; comparison means for comparing the normalized concentrations to a threshold value that, in the absence of a fire, has only a pre-selected small probability of being exceeded by a normalized concentration; and, alarm signal generator means for generating an alarm signal when any of the normalized concentrations exceeds the threshold value.
Claim 19
Dependent Claim
23 words
The apparatus of claim 15 wherein some of said at least two carbon dioxide sensors are positioned at different elevations within the room.
Claim 20
Dependent Claim
25 words
The apparatus of claim 15 wherein said normalization means further include means for calculating the standard deviation of the concentrations sensed at a particular time.
Claim 21
Dependent Claim
26 words
The apparatus of claim 15 wherein said normalization means further include means for calculating the standard deviation of successive values of one of the sensed concentrations.
Claim 22
Dependent Claim
64 words
The apparatus of claim 15 further comprising in combination: a sensor for detecting a variable other than carbon dioxide concentration and for producing an auxiliary electrical signal representative of the variable; and, inhibiting means connected to said alarm signal generator means and responsive to said auxiliary electrical signal for inhibiting transmission of said alarm signal when said auxiliary electrical signal has a certain value.
Claim 23
Dependent Claim
15 words
The apparatus of claim 1 wherein said variable other than carbon dioxide concentration is temperature.
Claim 24
Dependent Claim
20 words
The apparatus of claim 15 wherein said normalization means further comprise memory means for storing concentrations sensed at past times.
Claim 25
Dependent Claim
23 words
The apparatus of claim 21 wherein said comparison means further comprise means for comparing current sensed concentrations with concentrations sensed at past times.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1995-01-06 | 1995-07-08 | 1996-01-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-01-06 | 1999-07-08 | 2000-01-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-01-06 | 2003-07-08 | 2004-01-07 | $7700.00 | Window Closed / Lapsed |