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  For vehicles with engine, fuel is combusted in the engine cylinders with participation of oxygen, , and exhaust is vented to the air after catalytic treatment. Pistons in cylinders are driven and move, which are connected to the engine main shaft, and the shaft rotates to provide power for vehicles.

  It’s not complicated to calculate the ratio of fuel and oxygen (actually the air) ratio, however the engine output changes all the time since the vehicle may accelerate or slow down, climb up or stop to wait for the traffic lights, so the fuel injection shall be adjusted by the ECU (engine control unit) all the time. Oxygen concentration in the exhaust is an important indication for fuel injection amount, when it’s high that means fuel is too less (also called lean combustion), oppositely, fuel injection is too much (also called rich combustion) when oxygen concentration is low. Therefore, oxygen sensor is applied to detect oxygen concentration in exhaust, and the measured result can be transmitted to ECU to control fuel injection, therefore adjust air-fuel ratio (equivalence ratio) and keep the engine working at the highest efficiency.

  Also for the exhaust treatment, three way catalyst is commonly used, via which NOx, CO and hydrocarbon in the exhaust are converted into nitrogen, CO2, water and oxygen, therefore hazardous substance vented to the air can be controlled. To monitor the effect of catalytic system, oxygen sensor can be applied, to detect oxygen concentration and compare it with before catalytic treatment. In the case of same concentration are obtained, then it means catalytic system is not effective any more, and ECU will give failure alarm.

  Therefore, oxygen has two critical functions for the engine, the former is front oxygen sensor, and the latter is called back oxygen sensor. Their positions can be described as the figure above. Front O2 sensor is used for fuel injection control, and back O2 sensor is used to monitor catalytic system working. Zirconia ceramic oxygen sensor is the most widely used type for both, since it has high temperature resistance, strong anti-poisoning ability, also with good aging resistance and long service life. ATCERA can provide various zirconia oxygen sensor chip for global customers, please visit www.atcera.com for more information.