Patent ID: 6071476
Filing Date: 2000-06-06
Classification: G01N

Abstract:
A differential calorimetric hydrocarbon gas sensor for determining the concentration of hydrocarbon gas species in a gas flow comprising:a sensing element located within a sensing region and including a catalytic layer having a first catalyst and a second catalyst disposed on the catalytic layer, the first catalyst having an active region comprising a total combustible catalyst having an active metal component selected form the group consisting of: platinum, rhodium, palladium, iridium, ruthenium, and combinations thereof, and the second catalyst differing from the first catalyst in its catalytic activity for oxidation of hydrocarbons;temperature compensation circuitry operable to generate a sufficient quantity of heat for maintaining the first catalyst at a first substantially constant operating temperature and the second catalyst at a second substantially constant operating temperature;temperature reference circuitry operable to measure the sufficient quantity of heat generated by the temperature compensation circuitry;a diffusion barrier overlying the catalytic layer for controlling the rate at which the gas diffuses to the catalytic layer and for protecting the catalytic layer from scouring by the gas flow;a transport layer interposed between the diffusion barrier and the catalytic layer for further controlling the rate at which the gas flow diffuses to the catalytic layer;an oxygen source, the oxygen source and the sensing region being disposed on a region of the sensor that is commonly heated; andwhereby the concentration of hydrocarbon species in a gas flow can be determined from the sufficient quantity of heat generated by the temperature compensation circuitry and measured by the temperature reference circuitry.