| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for measuring gas concentration by which the NOx concentration and air/fuel ratio in a sample gas can be measured simultaneously and a composite gas sensor which can be used for the measurement. SOLUTION: A composite gas sensor is composed of a pump cell 21, a detecting cell 31, and a sensor cell 41 and the detecting cell 31 is connected to a detection circuit 32 provided with a first ammeter 321 and a power source 329. The pump cell 21 is connected to a pump circuit 22 provided with a second ammeter 221 and a variable power source 229 and the sensor cell 41 is connected to a sensor circuit 42 provided with a first voltmeter 421. The NOx concentration of a sample gas is measured based on the first ammeter 321 and, at the same time, the air/fuel ratio of the sample gas is measured based on the second ammeter 221 by controlling the variable power source 229 so that the detected value of the first voltmeter 229 may be maintained at a fixed value. |
