| 摘要 |
<P>PROBLEM TO BE SOLVED: To improve the accuracy for detecting a gas concentration in a desired gas concentration detection range. <P>SOLUTION: A current detecting resistor 32 is connected to a sensor element 10. A current signal is measured by the current detecting resistor 32, and outputted to a microcomputer 20. The microcomputer 20 implements an A/D conversion of the current signal, and implements an A/F calculation based on it. An element impedance is detected from a change in a current or a voltage when a voltage applied to the sensor element 10 is changed in a AC manner. Operational amplifiers 36, 37 are respectively connected to points A, B at both ends of the current detecting resistor 32. A gain of the operational amplifier 36 is 5. A gain of the operational amplifier 37 is 15. An A/F detection is implemented by an output from the operational amplifier 36 in the entire detection range of an air-fuel ratio. The A/F detection is implemented by an output from the operational amplifier 37 in a particular range including stoiciometry. <P>COPYRIGHT: (C)2009,JPO&INPIT |
