Process for determining the percentage of combustible gases in a gas mixture as well as their classification according to gas class factors

• US 5,513,125 A
• Filed: 04/05/1994
• Issued: 04/30/1996
• Est. Priority Date: 04/08/1993
• Status: Expired due to Fees

• Current Assignee: Dragerwerk AG
• Original Assignee: Dragerwerk AG
• Inventors: Kauschke, Wolfgang
• Primary Examiner(s): Voeltz, Emanuel T.
• Assistant Examiner(s): CHOI, KYLE JAEHUN
• Application Number:
  US08/223,442
• Time in Patent Office: 756 Days
• Field of Search: 364/496, 364/497, 364/498, 364/499, 73/23.2, 73/23.21, 73/23.31, 73/31.01
• 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 33/0047 Organic compounds

Abstract

In a process for determining the percentage of combustible gases in air by means of a detection element catalytically supporting the combustion, this detection element is heated with an excitation function according to a predeterminable current-voltage pattern, and the response function resulting from this is investigated with respect to the position of its maximum (differentiation). If a time interval limit (3) is exceeded by the maximum, a first gas type factor is sent to the evaluating circuit, and if the maximum does not reach the interval limit (3), a second gas type factor is determined and is evaluated as a calibrating value and for the classification of the combustible gases to be investigated.

Claims

1. Process for determining the percentage of combustible gases in air using a detection element catalytically supporting the combustion, the detection element being incorporated in a measuring circuit, the process comprising the steps of:

cyclically heating the detection element during a heating phase by applying a voltage according to a predeterminable current-voltage excitation function;

representing by a response function the course over a period of time a value of a signal created by the detection element and detected by the measuring circuit in the presence of the gas to be determined;

providing the excitation function with a pattern such that the response function passes through a maximum;

determining the time interval from the start of the rise of the response function until the maximum is reached;

comparing said time interval with a time interval limit; and

sending a class gas factor, with which the determination of the percentage of the gas to be determined is coupled with classification of the detected gas, to the evaluation circuit;

determining the percentage of gas to be detected by an evaluating circuit using characteristic properties appearing in the pattern of the response function.

2. Process according to claim 1, wherein:

said time interval limit is divided into a plurality of time interval sections and a position of said time interval within said time interval sections defines a gas class factor.

3. Process according to claim 2, wherein:

said time interval limit and said time interval sections are set in a range from T=0.1 sec to T=10 sec.

4. Process according to claim 1, wherein:

said gas class factor includes a first gas class factor having a value such that a first class of gas types is defined with said first gas class factor, whose gas type factors are related to the gas-type factor of methane and a second gas class factor having a value such that a second class of gas types is defined with it, whose gas type factors are related to the gas type factor of methanol, which is standardized to 1.

5. Process according to claim 4, wherein:

the class of gas-type factors standardized with methane comprises the gases ethane (1.4), propane (1.8), butane (2.2), ethine (2.3), benzene (2.6), and cyclohexane (2.7); and

the class of the gas-type factors standardized with methanol comprises the gases ethanol (1.2), acetone (1.3), 2-butanone (1.5), diethyl ether (1.5), ethyl acetate (1.5), n-hexane (1.5), 2-propyl alcohol (1.5), n-heptane (1.6), toluene (1.6), n-nonane (1.7), o-xylene (1.7), n-octane (1.9), and 1-butyl alcohol (2.0), wherein the decimal numbers in parentheses designate the gas type factor.

6. Process according to claim 1, wherein:

said response function is differentiated wherein the differential has at least one of a maximum and a minimum whose position on a time axis is used to determine a percentage of combustible gases and the type of gas.

7. Process for determining the percentage of combustible gases in air by means of a detection element catalytically supporting the combustion, the detection element being incorporated in a measuring circuit, the process comprising the steps of:

cyclically heating the detection element during a heating phase by applying a voltage according to a predeterminable voltage-current excitation function;

detecting a response function in the form of a course over time of a signal value supplied by the detection element in the presence of the gas to be detected;

differentiating said response function wherein the differential has at least one of a maximum and a minimum;

determining the percentage and type of the gas to be detected by an evaluating circuit using said one of said maximum and minimum appearing in the pattern of the differentiated response function whereby the excitation function is applied to the catalytically active detection element and the maximum and minimum of the curve of the differentiated response function is used to determine a percentage and the type of gas by comparison with known features of the response function.

8. Process according to claim 7, further comprising:

determining a time interval from a start of the rise of the differentiated response function until the maximum is reached;

comparing said time interval with a time interval limit to determine said type of gas.

9. Process according to claim 8, wherein:

said time interval limit is divided into a plurality of time interval sections and a position of said time interval within said time interval sections defines a gas class factor.

10. Process for determining the percentage of combustible gases in air by means of a detection element catalytically supporting the combustion, the detection element being incorporated in a measuring circuit, the process comprising the steps of:

cyclically heating the detection element during the heating phase by applying voltage according to a predeterminable current-voltage excitation function and detecting a response function in the form of the course over time of a signal value supplied by the detection element and detected by the measuring circuit, in the presence of the gas to be detected; and

using properties appearing in the response function pattern to determine a percentage of gas to be detected;

determining the area under the response function;

classifying a type of the gas dependent on said area.