Patent ID: 6740217
Filing Date: 2004-05-25
Classification: G01N

Abstract:
A gas sensor comprising:a gas cavity into which gasses consisting essentially of oxygen molecules and a specified gas are admitted through a given dispersion resistance; a pump cell including an oxygen ion conductive solid electrolyte member, a first pump cell electrode, and a second pump cell electrode which is exposed to the gas cavity, said pump cell being responsive to application of a voltage across the first and second pump cell electrodes to selectively pump oxygen molecules into and out of said gas cavity for adjusting a concentration of the oxygen molecules within said gas cavity to a desired value; a sensor cell including an oxygen ion conductive solid electrolyte member, a first sensor cell electrode, and a second sensor cell electrode which is exposed to said gas cavity, said sensor cell being supplied with electric power through the first and second sensor cell electrodes to produce an electric current as a function of a concentration of the specified gas within said gas cavity; a monitor cell including an oxygen ion-conducting member, a first monitor cell electrode, and a second monitor cell electrode which is exposed to said gas cavity, said oxygen monitor cell being supplied with electric power through the first and second monitor cell electrodes to produce an electric current as a function of a concentration of the oxygen molecules within said gas cavity; a sensor cell power supply working to supply the electric power to said sensor cell; a monitor cell power supply working to supply the electric power to said monitor cell; a sensor cell current detector measuring the current produced by said sensor cell, said sensor cell current detector being disposed between the second sensor cell electrode exposed to said gas cavity and said sensor cell power supply; a monitor cell current detector measuring the current produced by said monitor cell, said monitor cell current detector being disposed between the second monitor cell electrode exposed to said gas cavity and said monitor cell power supply; and a concentration measuring circuit working to determine a difference between the currents measured by said monitor cell current detector and said sensor cell current detector to provide a signal indicative of the concentration of the specified gas within said gas cavity.