Oxygen concentration detector and method of use thereof

Claim 1

In an oxygen concentration detector having an oxygen concentration sensor made of an oxygen ion conductive metal oxide which produces an electromotive force in accordance with the difference between an oxygen concentration in gas components of a gas under test and the oxygen concentration in a reference gas, including a first electrode formed on the side of said oxygen concentration sensor which is to be exposed to the gas under test, and a second electrode formed on the side of said oxygen concentration sensor which is to be exposed to said reference gas so that the electromotive force produced by said oxygen concentration sensor is measured across said first and second electrodes; the improvement comprising; (i) a first porous coating of a refractory metal oxide coated on the surface of said first electrode, the grain size of said first porous coating being finer than about 250 mesh and said first porous coating having pores through which the gas under test can pass; and (ii) a second porous coating of a refractory metal oxide coated on the surface of said first coating, the grain size of said second porous coating being about 250 to about 100 mesh and said second porous coating having pores whose average diameter is larger than that of the pores of said first coating.

Claim 9

A method of detecting the oxygen concentration in the exhaust gas comprising oxygen, phosphorus, lead and oil from an internal combustion engine comprising: a. exposing to said exhaust gas an oxygen concentration detector having an oxygen concentration sensor of an ion conductive metal oxide producing an electromotive force in accordance with the difference between the gas coponents of said exhaust gas and the oxygen concentration of a reference gas containing oxygen, said sensor including: (1) a first electrode formed on the portion of said sensor exposed to the exhaust gas; (2) a second electrode formed on the portion of said sensor exposed to said reference gas such that in operation an electromotive force is produced across said first and second electrodes; (3) a first porous coating of a refractory metal oxide coated on the surface of said first electrode, the grain size of said first porous coating being smaller than about 250 mesh and having pores therein through which said exhaust gas passes; (4) a second porous coating of a refractory metal oxide coated on the surface of said first coating, the grain size of said second coating being about 250 to about 100 mesh and having pores therein whose average diameter is larger than that of the pores of said first coating; b. exposing said second electrode to said reference gas; and c. measuring the electromotive force produced between said first and second electrodes thereby determining the oxygen concentration in said exhaust gas.

Claim 10

A method of detecting the oxygen concentration in the exhaust gas comprising oxygen, phosphorus, lead and oil from an internal combustion engine comprising: a. exposing to said exhaust gas an oxygen concentration detector having an oxygen concentration sensor of an ion conductive metal oxide producing an electromotive force in accordance with the difference between the gas coponents of said exhaust gas and the oxygen concentration of a reference gas containing oxygen, said sensor including: (1) a first electrode formed on the portion of said sensor exposed to the exhaust gas; (2) a second electrode formed on the portion of said sensor exposed to said reference gas such that in operation an electromotive force is produced across said first and second electrodes; (3) a first porous coating of a refractory metal oxide coated on the surface of said first electrode, the grain size of said first porous coating being smaller than about 250 mesh and having pores therein through which said exhaust gas passes; (4) a second porous coating of a refractory metal oxide coated on the surface of said first coating, the grain size of said second coating being about 250 to about 100 mesh and having pores therein whose average diameter is larger than that of the pores of said first coating; b. exposing said second electrode to said reference gas; and c. measuring the electromotive force produced between said first and second electrodes thereby determining the oxygen concentration in said exhaust gas.