Sensor for combustible gases
First Claim
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1. A sensor for a combustible gas comprising:
- a temperature sensitive element having a catalyst associated therewith to facilitate combustion of the combustible gas;
a shroud surrounding the temperature sensitive element and extending above a top surface of the temperature sensitive element;
a reaction vessel surrounding the shroud and forming a passageway there between for creating a flow of gas separated from the temperature sensitive element by the shroud and having a shaped downstream end for directing the flow inwardly starting at a point above the temperature sensitive element so that the flow of gas does not directly contact the temperature sensitive element, but reaches the temperature sensitive element substantially solely by diffusion; and
a heater coupled to the reaction vessel.
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Abstract
A combustible gas sensor comprises four glass insulated radially extended and symmetrical temperature sensitive elements which are coated with a porous ceramic but only two elements having a catalyst. The sensor is mounted inside a temperature controlled reactor vessel in a region of no temperature gradient into which a combustible gas mixture is admitted and reacted on the catalytic surfaces. The change in the resistance of the elements under the catalyst is a measure of the concentration of the combustible gas.
23 Citations
35 Claims
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1. A sensor for a combustible gas comprising:
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a temperature sensitive element having a catalyst associated therewith to facilitate combustion of the combustible gas; a shroud surrounding the temperature sensitive element and extending above a top surface of the temperature sensitive element; a reaction vessel surrounding the shroud and forming a passageway there between for creating a flow of gas separated from the temperature sensitive element by the shroud and having a shaped downstream end for directing the flow inwardly starting at a point above the temperature sensitive element so that the flow of gas does not directly contact the temperature sensitive element, but reaches the temperature sensitive element substantially solely by diffusion; and a heater coupled to the reaction vessel. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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26. A sensor for a combustible gas comprising:
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a reaction vessel having a chamber therein, the vessel having an open base end, an intermediate cylindrical portion, a shaped opposite end, a gas inlet for directing the gas into the base end, and a gas outlet for exhausting the gas from the shaped end; a heater coupled to the vessel; a sensor head within the cylindrical portion of the vessel comprising;
a metallic tubular end assembly having a base end and an opposite end;
a cylindrical insulating unit hermetically sealed within the tubular end assembly;
a plurality of conducting wires, each one of the wires hermetically sealed in the insulating unit and passing there through;
a ceramic table seated on the opposite end of the tubular end assembly and having a plurality of holes extending axially there through, a sensor plate positioned perpendicular to the axis of the sensor above the ceramic table and rigidly connected by a plurality of electrically conducting leads to the plurality of conducting wires via the holes;
the sensor plate comprising a thin substrate, an even number of substantially identical temperature sensitive resistive elements arranged symmetrically on the substrate, half of the elements being sensing elements and having a catalyst associated therewith to facilitate combustion of the combustible gas in the vicinity of the sensing elements thereby increasing their temperature, the remainder of the elements being reference elements not having a catalyst associated therewith; anda cylindrical shroud surrounding the sensor head and extending from the base end of the tubular assembly to between the sensor plate and the shaped end and forming an annular passageway between the reaction vessel and the shroud for creating a flow of gas separated from the sensor plate by the shroud and directing the flow inwardly starting at a point beyond the sensor plate so that the flow of gas does not directly contact the sensor plate, but reaches the sensor plate substantially solely by diffusion, wherein the gas inlet communicates with the annular passageway. - View Dependent Claims (27, 28, 29, 30, 31, 32, 33, 34, 35)
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Specification