Introduction of NOx sensor

N0x sensor is one of the most critical components in the post-processing system. Its role in the application of National IV, National V, Beijing IV, Beijing V phase is: during engine operation Medium, the N0x concentration of the exhaust pipe exhaust of the engine is detected from time to time to detect whether the N0x emission meets the regulatory requirements.

The N0x sensor is a completed component consisting of an inductive probe and control module and a wiring harness. The internal self-diagnosis function reports the monitoring information to the ECU via CAN bus communication.

1, NOx sensor physical installation:

1.N0x sensor installation temperature requirement: N0x sensor The installation should be careful not to install at an excessive temperature. It is recommended to keep away from the surface of the exhaust pipe and the SCR case. A heat shield and insulation cotton must be installed during installation. The ambient temperature of the sensor ECU installation is evaluated. It is recommended that the optimal operating temperature of the N0x sensor is not higher than 85 degrees.

2. Wire harness and connector installation requirements: Fix the wire harness and waterproof. Keep the line loose during the installation and use of the N0x sensor. The entire wire harness should not be bent too much to prevent external force or excessive force. The wire harness is detached, try to avoid the wire harness and the N0x sensor being exposed. If the metal wire is exposed, it should be wrapped with tape, and the wire joint should not be affected by oil, debris, mud, etc., and it should be waterproof. Otherwise, the wire harness will occur. Sensor failure due to water ingress.

2,N0xNitrogen oxide sensor appearance:2.12.8

1. Nitrogen oxide sensors are 12V and 24V.

2. The NOx sensor has a 4-pin and a 5-pin plug.

3. The brands of nitrogen oxide application models include: Cummins, Weichai, Yuchai, and Heavy Duty Truck.

3, the NOx sensor working process is explained in detail:

The main function of the N0x sensor is to detect the exhaust gas. Whether the N0x concentration value is out of limits, and whether the catalytic converter muffler is aging or removed.

The N0x sensor communicates with the control unit via the CAN bus and has its own diagnostic function. After the sensor self-test has no fault, the control unit instructs the heater to heat the N0x sensor. If the sensor signal is not received within the heating process if the maximum heating time limit is exceeded, it is determined that the sensor heating is not reliable.

1. “No power status”:

A. In this state, 24V power is not supplied to the sensor.

B. This is the normal state of the sensor when the body igniter switch is off.

C. The sensor does not have any output at this time.

2. “Powered—sensor inactive”:

A. At this point the power has been supplied to the sensor via the ignition switch.

B. The sensor enters the preheating phase. The purpose of preheating is to evaporate all moisture on the sensor head.

C. The preheating phase lasts for approximately 60 seconds.

3. When the ignition switch is turned on, the N0x sensor will heat up to 100 °C.

4. After waiting for the ECM to issue a “dew point” temperature signal (Dew point):

“Dew point” temperature means: there will be no exhaust system inside this temperature Moisture that can damage the N0x sensor. The current dew point temperature is set to 120 ° C, and the temperature value is the value measured with reference to the EGP outlet temperature sensor.

5. When the sensor receives the dew point temperature signal from the ECM, the sensor will heat itself to a certain temperature (maximum 800 ° C) – Note: If the sensor head is exposed to water, it will cause The sensor is damaged.

6. After heating to the operating temperature, the sensor begins normal measurement.

7. The NOx sensor sends the measured NOx value to the ECM via the CAN bus. The engine ECM uses this information to monitor the NOx emissions from time to time.

4How does the NOx sensor work:

How it works: Nitrox oxygen sensor The core component is the Zr02 zirconia ceramic tube of the ferry, which is a solid electrolyte with sintered porous platinum (Pt) electrodes on both sides. When heated to a certain temperature (600-700 ° C), due to the difference in oxygen concentration on both sides, zirconia will produce a chemical reaction, and the charge moves on both sides of the electrode, and the moving charge generates a current. According to the magnitude of the generated current, the concentration of oxygen is reflected, and the concentration of oxygen is fed back to the controller to calculate the current nitrogen-oxygen concentration and transmitted to the ECU through the CAN bus.

5, sensor probe self-protection features and precautions:

When the ignition is turned on, N0x The sensor will heat up to 100 °C. After waiting for the DCU to send a “dew point” temperature signal, the sensor will self-heat to a certain temperature after receiving the dew point temperature signal from the DCU (maximum 800 ° C. Note: If the sensor touches the water at this time will cause Sensor damage)

Dew point protection: Because the NOx sensor itself requires a higher temperature for the electrode to operate, the NOx sensor has a ceramic structure inside. When the ceramic is exposed to water at high temperatures, it will burst. Therefore, the nitrogen-oxygen sensor will set a dew point protection function. The function of this function is to wait for a period of time after detecting that the discharge temperature reaches a certain temperature. The computer version believes that at such a high temperature, after such a long time, even if there is water on the sensor, it can be dried by the high-temperature exhaust gas.

6,Other knowledge of nitrogen oxide sensors:

A type of NOx sensor is called “Gortex” * Material to ensure fresh air enters the reference comparison space inside the sensor. It is therefore important to ensure that this vent is unobstructed, and that impurities should be prevented from covering or covering the vent. In addition, sensors should be installed as much as possible after painting and painting the body. If the paint painting and painting work must be carried out after the sensor is installed, the vents of the sensor must be properly protected. After the paint painting work is completed, the protective materials are removed to ensure the normal operation of the sensor.

*Gortex(Goltex) is a soft and easy-to-mold material that looks like a sponge and is resistant to high and low temperatures, wind and rain. ; is a common material for artificial blood vessels.

7,N0xNOx sensor parameters:

Output Parameters Symbol Min Max
nitrogen oxide concentration [N0x] 0ppm 3000ppm
Oxygen concentration [O2] 0% 21%

Introduction to NOx Sensors