Method and system for gas detection

• US 5,526,280 A
• Filed: 04/28/1994
• Issued: 06/11/1996
• Est. Priority Date: 04/28/1994
• Status: Expired due to Fees

• Current Assignee: Atwood Mobile Products LLC (Dometic Group AB)
• Original Assignee: Atwood Industries, Inc. (Stanley Black & Decker, Inc.)
• Inventors: Field, D. George, Banta, Kevin D., Consadori, Franco
• Primary Examiner(s): Ramirez, Ellis B.
• Assistant Examiner(s): Stamber, Eric W.
• Application Number:
  US08/234,013
• Time in Patent Office: 775 Days
• Field of Search: 364/496, 364/497, 364/498, 364/499, 340/632, 340/633, 340/634, 73/23.2, 73/23.31, 73/25.01, 73/31.05, 422/83, 422/94, 422/95, 422/98, 436/137, 436/151, 338/34
• US Class Current: 702/24
• CPC Class Codes: G01N 27/16 caused by burning or catalytic oxidation of surrounding material to be tested, e.g. of gas
• CPC Class Codes: G01N 33/0063 using a threshold to release an alarm or displaying means

Abstract

A system and method for using a gas detecting device that conducts electricity increasingly for increasing concentration of a gas being detected. The temperature of a gas sensor element is regulated to first burn-off impurities on the surface thereof, and then to cool down the gas sensor element to a temperature at or above which the gas catalyzes. During catalyzation, the sensor element conducts and electrically signals a microprocessor concentration data, which microprocessor controls a three color LED so as to emit a color pattern indicative of the concentration level of the gas. A sum of previously measured concentration levels is taken to gauge exposure to the gas over a period of time. The gas detection system includes a self-calibration routine that can be run prior to normal use by successive exposure to varying concentrations of gas to determine the sensor element-specific reaction. The sensor element output at each known concentration level is stored in nonvolatile memory during the self-calibration routine, which stored calibration data is compared to values measured during normal operation to accurately detect gas concentration levels. Audible alarms sound when the sum of previously measured concentration levels exceeds a predetermined hazardous level.

Claims

1. A system for monitoring a concentration of gaseous carbon monoxide and for automatically recording and displaying gaseous carbon monoxide concentration data, said system comprising:

means for sensing the concentration of the gaseous carbon monoxide and for outputting an electrical signal proportional to the concentration of the gaseous carbon monoxide, the sensing means being placed in fluid communication with the gaseous carbon monoxide, said sensing means comprising;

a catalyzing element and a means for cyclically heating said catalyzing element, said gaseous carbon monoxide catalyzing when in fluid communication with the catalyzing element that is heated to a predetermined catalyzing temperature range, wherein the cyclical heating means heats said catalyzing element by application of a first predetermined electrical voltage for a first predetermined time so as to cause the catalyzing element to be heated above the predetermined catalyzing temperature range, and wherein the cyclical heating means heats said catalyzing element by application of a second predetermined electrical voltage for a second predetermined time so as to cause the catalyzing element to be heated within the predetermined catalyzing temperature range, the sensing means outputting an electrical signal proportional to the concentration of the gaseous carbon monoxide when the catalyzing element is heated within the predetermined catalyzing temperature range;

means for converting said signal output from said sensing means into a series of corresponding digital signals;

data memory means for storing a concentrations history array, said concentrations history array having stored therein for chronological order from an oldest previously stored concentration level of the gaseous carbon monoxide to a newest concentration level of the gaseous carbon monoxide a plurality greater than two of previously stored levels of concentration of the gaseous carbon monoxide, for storing a total exposure level, and for storing a calibration table of values, each value in the calibration table of values corresponding to a predetermined response of the sensing means to being placed in fluid communication with a predetermined concentration of gaseous carbon monoxide;

digital processor means for processing said digital signals so as to electronically monitor, display and record the concentration of the gaseous carbon monoxide by performing a plurality of programmed steps comprising;

comparing the digital signals with said values of the calibration table of values;

deriving data from said comparison step representing a derived gas level that corresponds to the predetermined response of the sensing means to being placed in fluid communication with the corresponding predetermined concentration of gaseous carbon monoxide;

electronically storing the derived gas level in the concentrations history array, said concentrations history array having stored therein a plurality greater than two of previously stored levels of concentration of the gaseous carbon monoxide, each of said previously stored levels of concentration of the gaseous carbon monoxide being stored therein in chronological order from an oldest previously stored concentration level of the gaseous carbon monoxide to at least two chronologically more recent concentration levels of the gaseous carbon monoxide, said derived gas level being stored in said concentrations history array so as to replace the oldest previously stored concentration level of gaseous carbon monoxide;

summing said plurality greater than two of previously stored levels of concentration of the gaseous carbon monoxide to arrive at the total exposure level;

electronically storing the total exposure level in the data memory means;

automatically displaying the derived gas level in a visually perceptible manner to a system user; and

automatically displaying in a visually perceptible manner to the system user a diagnostic when the total exposure level exceeds a predetermined alarm level;

program memory means for storing machine-readable instructions utilized by said digital processor means to carry out said plurality of programmed steps; and

display means, electrically connected to said digital processor means, for outputting a visual display of the derived gas level, and for outputting a visual display of the diagnostic when the total exposure level exceeds the predetermined alarm level.

2. The system as defined in claim 1, wherein the display means is a single LED that radiates light in a predetermined patterned sequence corresponding to the derived gas level, and that radiates light in a predetermined patterned sequence corresponding to the diagnostic.

3. The system as defined in claim 2, wherein the single LED is a multi-color LED, and wherein the predetermined patterned sequences corresponding to the derived gas level and the diagnostic are both patterned sequences of a plurality of colors of radiated light.

4. The system as defined in claim 1, further comprising a means for producing a sound, and wherein the sound producing means produces an audible alarm when the total exposure level in the data memory means exceeds the predetermined alarm level.

5. The system as defined in claim 1, further comprises a means for measuring an ambient temperature, and wherein the data memory means has stored therein a temperature compensation table of temperature compensation values, each temperature compensation value in the temperature compensation table of temperature compensation values corresponding to a predetermined response of the sensing means to a predetermined range of temperatures, and wherein the programmed step of said plurality of programmed steps of deriving data from said comparison step representing a derived gas level further comprises the steps of:

obtaining an ambient temperature from the ambient temperature measuring means, and

adjusting the derived gas level by a temperature compensation value in said temperature compensation table of temperature compensation values corresponding to the ambient temperature obtained from the ambient temperature measuring means.

6. The system as defined in claim 1, wherein the predetermined alarm level corresponds to a predetermined gas concentration exposure over a predetermined time that would cause a predetermined carboxyhemoglobin condition of a theoretical human.

7. The system as defined in claim 1, wherein the cyclical heating means heats said catalyzing element above said predetermined catalyzing temperature range so as to remove a deposit of impurities therefrom.

8. The system as defined in claim 7, wherein the cyclical heating means repeatedly heats said catalyzing element within and above said predetermined catalyzing temperature range, whereby repeatedly the derived gas level is obtained and the catalyzing element has removed therefrom said deposit of impurities.

9. The system as defined in claim 1, wherein the second predetermined voltage is approximately one half of the first predetermined voltage, and the first predetermined time is not greater than twice the second predetermined time.

10. The system as defined in claim 9, wherein the second predetermined voltage is approximately 3 volts, and the second predetermined time is 30 seconds.

11. The system as defined in claim 1, wherein the catalyzing element is surrounded, at least in part, by an active charcoal filter.

12. The system as defined in claim 1, further comprising means, activateable by the system user, for simulating the predetermined alarm level when the total exposure level in the data memory means is not greater than the predetermined alarm level, and wherein the concentrations history array in the data memory means is not changed, whereby the display means outputs a visual display of the diagnostic.

13. A system for monitoring a concentration of a gas and for automatically recording and displaying gas concentration data, said system comprising:

means for sensing the concentration of the gas and for outputting an electrical signal proportional to the concentration of the gas, the sensing means being placed in fluid communication with the gas;

means for converting said signal output from said sensing means into a series of corresponding digital signals;

data memory means for storing a concentrations history array, said concentrations history array having stored therein in chronological order from an oldest previously stored concentration level of the gas to a newest concentration level of the gas a plurality greater than two of previously stored levels of concentration of the gas, for storing a total exposure level, and for storing a calibration table of values, each said value in the calibration table corresponding to a predetermined response of the sensing means to being placed in fluid communication with a predetermined concentration of gas;

digital processor means for processing said digital signals so as to electronically monitor, display and record the concentration of the gas by performing a plurality of programmed steps comprising;

comparing the digital signals with values of the calibration table;

deriving data from said comparison step representing a derived gas level that corresponds to the predetermined response of the sensing means to being placed in fluid communication with the corresponding predetermined concentration of gas;

electronically storing the derived gas level in the concentrations history array, said concentrations history array having stored therein a plurality greater than two of previously stored levels of concentration of the gas, each of said previously stored levels of concentration of the gas being stored therein in chronological order from an oldest previously stored concentration level of the gas to at least two chronologically more recent concentration levels of the gas, said derived gas level being stored in said concentrations history array so as to replace the oldest previously stored concentration level of gas in the data memory means;

summing said plurality greater than two of previously stored levels of concentration of the gas to arrive at the total exposure level;

electronically storing the total exposure level in the data memory means;

automatically displaying the derived gas level in a visually perceptible manner to a system user; and

automatically displaying in a visually perceptible manner to the system user a diagnostic when the total exposure level in the data memory means exceeds a predetermined alarm level;

program memory means for storing machine-readable instructions utilized by said digital processor means to carry out said plurality of programmed steps; and

display means, electrically connected to said digital processor means, for outputting a visual display of the derived gas level, and for outputting a visual display of the diagnostic when the total exposure level exceeds the predetermined alarm level.

14. The system as defined in claim 13, wherein the display means is a single LED that radiates light in a predetermined patterned sequence corresponding to the derived gas level, and that radiates light in a predetermined patterned sequence corresponding to the diagnostic.

15. The system as defined in claim 14, wherein the single LED is a multi-color LED, and wherein the predetermined patterned sequences corresponding to the derived gas level and the diagnostic are both patterned sequences of a plurality of colors of radiated light.

16. The system as defined in claim 13, further comprising a means for producing a sound, and wherein the sound producing means produces an audible alarm when the total exposure level in the data memory means exceeds the predetermined alarm level.

17. The system as defined in claim 13, further comprises a means for measuring an ambient temperature, and wherein the data memory means has stored therein a temperature compensation table of temperature compensation values, each temperature compensation value in the temperature compensation table of temperature compensation values corresponding to a predetermined response of the sensing means to a predetermined range of temperatures, and wherein the programmed step of said plurality of programmed steps of deriving data from said comparison step representing a derived gas level further comprises the steps of:

obtaining an ambient temperature from the ambient temperature measuring means, and

adjusting the derived gas level by a temperature compensation value in said of temperature compensation table of temperature compensation values corresponding to the ambient temperature obtained from the ambient temperature measuring means.

18. The system as defined in claim 13, wherein the predetermined alarm level corresponds to a predetermined gas concentration exposure over a predetermined time that would cause a predetermined blood gas concentration of the gas in a hemoglobin content in a vascular blood supply of a theoretical human.

19. The system as defined in claim 13, wherein said sensing means further comprises a catalyzing element and a means for cyclically heating said catalyzing element, said gas catalyzing when in fluid communication with the catalyzing element that is heated to a predetermined catalyzing temperature range, the sensing means outputting an electrical signal proportional to the concentration of the gas when the catalyzing element is heated within the predetermined catalyzing temperature range.

20. The system as defined in claim 19, wherein the cyclical heating means heats said catalyzing element above said predetermined catalyzing temperature range so as to remove a deposit of impurities therefrom.

21. The system as defined in claim 20, wherein the cyclical heating means repeatedly heats said catalyzing element within and above said predetermined catalyzing temperature range, whereby repeatedly the derived gas level is obtained and the catalyzing element has removed therefrom said deposit of impurities.

22. The system as defined in claim 19, wherein the cyclical heating means heats said catalyzing element by application of a first predetermined electrical voltage for a first predetermined time so as to cause the catalyzing element to be heated above the predetermined catalyzing temperature range, and wherein the cyclical heating means heats said catalyzing element by application of a second predetermined electrical voltage for a second predetermined time so as to cause the catalyzing element to be heated within the predetermined catalyzing temperature range.

23. The system as defined in claim 22, wherein the gas is essentially composed of carbon monoxide.

24. The system as defined in claim 23, wherein the catalyzing element is surrounded, at least in part, by an active charcoal filter.

25. The system as defined in claim 22, wherein the second predetermined voltage is approximately one half of the first predetermined voltage, and the first predetermined time is not greater than twice the second predetermined time.

26. The system as defined in claim 25, wherein the second predetermined voltage is approximately 3 volts, and the second predetermined time is 30 seconds.

27. The system as de lined in claim 13, further comprising means, activateable by the system user, for simulating the predetermined alarm level when the total exposure level in the data memory means is not greater than the predetermined alarm level, and wherein the concentrations history array in the data memory means is not changed, whereby the display means outputs a visual display of the diagnostic.

28. A system for monitoring a concentration of a gas and for automatically recording and displaying concentration data, comprising:

means for sensing the concentration of the gas and for outputting an electrical signal proportional to the concentration of the gas, the sensing means being placed in fluid communication with the gas;

means for converting said signal output from said sensing means into a series of corresponding digital signals;

digital processor means for processing said digital signals so as to electronically monitor, display and record the concentration of the gas by performing a plurality of programmed steps comprising;

deriving data from said digital signals which represents a level of concentration of the gas;

electronically storing the level of concentration of the gas as a newest concentration level of the gas in a concentrations history array, said concentrations history array having stored therein in chronological order from an oldest previously stored concentration level of the gas to the newest concentration level of the gas a plurality greater than two of previously stored levels of concentration of the gas;

subtracting the oldest previously stored concentration level of the gas from a sum of the plurality of previously stored concentration levels of the gas to arrive at an intermediate sum;

adding the level of the concentration of the gas to the intermediate sum to arrive at a total exposure level;

electronically storing the total exposure level for later retrieval and output;

automatically displaying the level of concentration of the gas in a visually perceptible manner to a system user; and

automatically displaying in a visually perceptible manner to the system user a diagnostic when the total exposure level exceeds a predetermined alarm level;

data memory means for storing the total exposure level and the concentrations history array;

program memory means for storing machine-readable instructions utilized by said digital processor means to carry out said plurality of programmed steps; and

display means, electrically connected to said digital processor means, for outputting a visual display of the level of concentration of the gas and a visual display of the diagnostic when the total exposure level exceeds the predetermined alarm level.

29. A system for monitoring a concentration of a gas and for automatically recording and displaying gas concentration data, said system comprising:

means for sensing the concentration of the gas, said sensing means comprising;

a catalyzing element;

a heating material separate from and in thermal communication with said catalyzing element;

a means for cyclically heating said heating material, said cyclical heating means heating said catalyzing element by application of a first predetermined electrical voltage for a first predetermined time to said heating material so as to cause the catalyzing element to be heated above a catalyzing temperature range of the gas, and wherein the cyclical heating means heats said heating material by application of a second predetermined electrical voltage for a second predetermined time so as to cause the catalyzing element to be heated within the catalyzing temperature range of the gas;

a means for continuous sensing of the catalyzing element, wherein said continuous sensing means senses said catalyzing element when the catalyzing element is heated both above and within the catalyzing temperature range of the gas, and for continuously outputting an electrical signal proportional to the concentration of the gas in fluid communication with the catalyzing element when the catalyzing element is heated to a temperature within the catalyzing temperature range of the gas;

means for converting said electrical signal output from said means for continuous sensing of the catalyzing element into a series of corresponding digital signals;

digital processor means for processing said digital signals so as to electronically monitor, display and record the concentration of the gas in fluid communication with the catalyzing element by performing a plurality of programmed steps comprising;

deriving data from said digital signals which represents a level of concentration of the gas; and

automatically displaying the level of concentration of the gas in a visually perceptible manner to a system user;

program memory means for storing machine-readable instructions utilized by said digital processor means to carry out said plurality of programmed steps; and

display means, electrically connected to said digital processor means, for outputting a visual display of the level of the concentration of the gas.

30. The system as defined in claim 29, wherein an electrical voltage is continuously applied to the heating material by the cyclical heating means;

and

wherein said cyclical heating means and said continuous sensing means are separate electrically isolated electrical circuits.

31. The system as defined in claim 29, wherein the first predetermined time and the continuous second predetermined time are a cycle having a duration of less than 90 seconds, and wherein the catalyzing element catalyzes all of the gas in fluid communication therewith during the first predetermined time, and wherein the temperature of the catalyzing element drops below the catalyzing temperature range of the gas during the second predetermined time.

32. The system as defined in claim 29, further comprising:

data memory means for storing a concentrations history array, said concentrations history array having stored therein in chronological order from an oldest previously stored concentration level of the gas to a newest concentration level of the gas a plurality greater than two of previously stored levels of concentration of the gas, for storing a total exposure level, and for storing a calibration table of values, each said value in the calibration table of values corresponding to a predetermined response of the sensing means to being placed in fluid communication with a predetermined concentration of the gas;

wherein the plurality of programed steps performed by the digital processor means further comprises;

comparing the digital signals with said values of the calibration table of values;

deriving data from said comparison step representing a derived gas level that corresponds to the predetermined response of the sensing means to being placed in fluid communication with the corresponding predetermined concentration of the gas, wherein said level of concentration of the gas is the derived gas level;

electronically storing the derived gas level in the concentrations history array, said concentrations history array having stored therein a plurality greater than two of previously stored levels of concentration of the gas, each of said previously stored levels of concentration of the gas being stored therein in chronological order from an oldest previously stored concentration level of the gas to at least two chronologically more recent concentration levels of the gas, said derived gas level being stored in said concentrations history array so as to replace the oldest previously stored concentration level of the gas;

summing said plurality greater than two of previously stored levels of concentration of the gas to arrive at the total exposure level;

electronically storing the total exposure level in the data memory means; and

automatically displaying in a visually perceptible manner to the system user a diagnostic when the total exposure level exceeds a predetermined alarm level; and

wherein said display means is also for outputting a visual display of the diagnostic when the total exposure level exceeds the predetermined alarm level.

33. The system as defined in claim 29, wherein the gas is gaseous carbon monoxide.