Gas sensor
AssigneeCapteur Sensors & Analysers, Ltd.
InventorDavid Edward Williams
Life of this patent
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Abstract
A method for determining the presence of a first gas in a second gas uses a gas sensor made up of at least two pairs of electrodes, each pair of electrodes having different spacing between the electrodes. The electrodes of the gas sensor have surfaces that are reactive to the gases under investigation. The gas sensor is exposed to the gases, and the electrical resistances between the pairs of electrodes are measured over a period of time. `The results are compared with a calibration curve to determine if the first gas is present in the second, and to determine of the sensor is malfunctioning.
Claims11
A method of determining the concentration of at least one gas in a gaseous mixture, using a gas sensor comprising:
- a body of material having an electrical conductivity sensitive to the presence of said at least one gas in said gaseous mixture, said body having an active surface, and a plurality of electrodes in contact with said body and defining at least two electrode pairs, each electrode pair consisting of two electrodes of said plurality of electrodes spaced apart, with the spacing between the electrodes of an electrode pair, or the distance between an electrode pair and an active surface, being different as between one said electrode pair and another, said method comprising the steps of:
- (1) exposing the said active surface to a series of gaseous mixtures each having different known concentration of said at least one gas and wherein said at least one gas reacts on said active surface;
- (2) measuring the electrical resistance between the electrodes of each said electrode pair, for each member of said series, thereby obtaining for each said electrode pair measured values of the resistance of that pair;
- (3) creating a series of calibration values from parameters derived from said measured values, which series relates said parameters to said known concentrations of said at least one gas in the gaseous mixture;
- (4) exposing the said active surface to the said gaseous mixture containing the said at least one gas whose concentration in the mixture it is wished to determine so that at least one gas reacts on said active surface;
- (5) measuring the electrical resistance between the electrodes of each said electrode pair during step (4);
- (6) comparing a parameter, derived from the said measured values of step (5), with said series of calibration values to determine the concentration of said at least one gas in the said gaseous mixture;
- (7) creating, from the measurements of step (2), a calibration datum constituting at least one operating line or an operating surface under conditions when it is known that the sensor is not malfunctioning;
- (8) comparing the measurements of step (5) with said calibration datum and using any deviation therebetween to indicate a malfunction of the sensor.
Dependencies are inferred from the claim text.