Oxygen sensing device having solid electrolyte cell and means for supplying controlled current thereto

Claim 1

In a device for detecting concentrations of oxygen in gases, the device having an oxygen sensor element (10) which has a ceramic substrate (12) provided with a heater (14) and a laminate of a reference electrode layer (18), an oxygen ion conductive solid electrolyte layer (20) and a measurement electrode layer (22) supported on the substrate, a power supplying means (50,R 1 ,R 2 ,R 3 ) for applying a controlled voltage (V H ) to the heater in the oxygen sensor element so as to maintain the heater at a predetermined temperature by controlling the resistance of the heater to a constant value, and a current supplying means for supplying a controlled DC current (I C ) to the sensor element such that the current flows in the solid electrolyte layer from the reference electrode layer toward the measurement electrode layer to cause oxygen ions to migrate in the solid electrolyte layer from the measurement electrode layer toward the reference electrode layer to thereby maintain a reference oxygen partial pressure at the interface between the reference electrode layer and the solid electrolyte layer, the improvement comprising a link means (R 4 ,R 5 ) for electrically associating said current supplying means with said power supplying means to transmit a voltage signal (E 3 ) representative of said voltage (V H ) applied to said heater to said current supplying means, said current supplying means (56,R 6 ) having the function of varying the intensity of said current (I C ) in inverse proportion to the magnitude of said voltage (V H ) applied to said heater.