| 摘要 |
PURPOSE:To keep the temperature of the sensor constant at all times, by forming a bridge circuit by combining a heater incorporated in the oxygen sensor and resistors, detecting the unbalanced potential, and controlling the voltage to be applied to the heater. CONSTITUTION:The oxygen sensor 1, which measures the oxygen concentration in a combustion engine and the like, is formed by a detecting part wherein the heater 2 is embedded in an insulating substrate 3, a reference side electrode 4, an oxygen ion conducting solid electrolyte 5, and a measuring side electrode 6 are laminated. The bridge circuit is formed by combining the heater 2 and the resistors R1, R2, and R3. The unbalanced voltage thereof is compared by a comparator 22 and given to a power amolifier 21. The voltage to be applied to the bridge circuit is varied so that the unbalanced voltage becomes zero. Therefore the temperature of the sensor 1 can be readily controlled to make it constant, without directly detecting the temperature of the sensor 1 by a temperature detecting element such as a thermocouple. |
