| 摘要 |
PURPOSE:To compensate changes in resistance due to deterioration of a heater element by controlling quantity to electric power to a heater for heating an O2 sensor element so that at least either one of a maximum and minimum values of outputs from the O2 sensor becomes not greater than a specified reference value. CONSTITUTION:An oxygen concentration sensing part 2 in an exhaust concentration sensor 1 is heated and maintained at a specified temperature by means of a heater 5. Heat output of the heater 5 is controlled by a quantity VH of electric power supplied from a heater control circiut 9. The heater control circuit 9 controls the quantity of electric power VH so that at least either one of a maximum and a minimum values of outputs from an oxygen concentration sensor part 2 becomes not greater than a specified reference value.
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