Working principle of NOx sensor

Working principle of nitrogen oxygen sensor 

The nitrogen oxygen sensor is used to measure the nitrogen oxygen concentration in engine exhaust, in order to meet the needs of closed-loop control of the engine after treatment system and the on-board OBD diagnostic system. It can calculate the conversion efficiency of nitrogen oxides in real time and control the original emission of nitrogen oxides in the engine. Adopting more precise closed-loop control logic can improve fuel economy.  

Front NOX sensor:

Detect the concentration of NOX and oxygen in the original exhaust of the engine, and transmit the corresponding signals to the ECU for calculating and controlling the amount of urea injection. 

Rear NOX sensor:

Used for OBD monitoring, it mainly detects the concentration of NOx in the exhaust gas, and calculates the conversion efficiency in combination with the front NOx sensor. The conversion efficiency can reach over 95%, achieving closed-loop control of urea injection.

 

NOx sensor type

The nitrogen oxygen sensors used in the current national six vehicle models are divided into two types according to the form of wire harness connectors. One type is a five pin interface nitrogen oxygen sensor, which is the same as the front and rear nitrogen oxygen sensors. The signal is distinguished by the five pin address line of the front nitrogen oxygen sensor; Another type is a four pin interface nitrogen oxygen sensor, which has different wiring harness connectors. Incorrect assembly can cause the wiring harness connectors to fail to connect.

 

Operating principle of NOx sensor 

The zirconia chamber is heated to 600 ° C.

When current is applied to both sides of the chamber wall, the zirconia crystallization chamber can pump oxygen through the chamber wall. 

 

There are two chambers:

1. The first chamber is used to remove oxygen present in the engine exhaust.

2. The exhaust gas that removes oxygen enters the second chamber, where the platinum coating can decompose NO and NO2 into nitrogen (N2) and oxygen (O2) at 600C.

3. The second chamber measures the amount of oxygen pumped out while pumping out oxygen. If there is no O2, then there is no NOx.