Combustible gas measurement
First Claim
1. A method of determining the concentration of combustible engine exhaust gas elements, comprising the steps of:
- exposing a catalyzed temperature sensitive element which is coated with a catalyst and an inert temperature sensitive element to a flow of internal combustion engine exhaust gas;
applying a pulse of electrical current through the catalyzed and the inert elements;
determining the electrical resistance of the catalyzed and of the inert elements;
generating signals representing the concentration of combustible engine exhaust gas elements as a predetermined function of the determined electrical resistance.
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Abstract
A pulsed measurement technique for calorimetric sensors provides a short current pulse through catalyzed and inert sensor elements to minimize self heating while providing for sensor resistance measurement, so that a determination of the level of catalytic activity at the surface of the catalyzed element may be made for sensing the concentration of combustible elements of automotive internal combustion engine exhaust gas. Exhaust gas temperature measurement is provided by monitoring the inert element resistance. Exhaust gas flow rate measurement is provided by heating the inert element for a short heating period, and then removing the heat source while monitoring the time rate of return to the known initial inert element temperature.
93 Citations
12 Claims
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1. A method of determining the concentration of combustible engine exhaust gas elements, comprising the steps of:
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exposing a catalyzed temperature sensitive element which is coated with a catalyst and an inert temperature sensitive element to a flow of internal combustion engine exhaust gas; applying a pulse of electrical current through the catalyzed and the inert elements; determining the electrical resistance of the catalyzed and of the inert elements; generating signals representing the concentration of combustible engine exhaust gas elements as a predetermined function of the determined electrical resistance. - View Dependent Claims (2, 3, 4, 5, 6)
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7. An apparatus for sensing concentration of combustible elements in internal combustion engine exhaust gas, comprising:
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a first and a second temperature sensitive elements exposed to internal combustion engine exhaust gas, the first element being coated with a catalyst so as to catalytically react with the combustible elements in the engine exhaust gas, wherein energy generated in the catalytic reaction elevates the temperature of the first element above the temperature of the second element; a current pulse generating circuit for generating a current pulse and for applying the current pulse through the first and second temperature sensitive elements; a voltage sampling circuit for sampling voltages across the first and the second temperature sensitive elements while the current pulse is passing through the elements; concentration determining means for determining the concentration of the combustible elements in the engine exhaust gas as a predetermined function of the sampled voltages. - View Dependent Claims (8, 9, 10, 11, 12)
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Specification