​SYHOWER brings you an introduction to NOx sensor

The NOx Sensor is a core component in the vehicle exhaust emission control system. It is primarily used to detect the concentration of nitrogen oxides (NOx, including N₂O, NO, NO₂, etc.) in engine exhaust and provides real-time data feedback to the on-board electronic control unit (ECU) to achieve precise emission control. ‌

Working Principle and Structure: This sensor typically operates based on an electrochemical principle, utilizing solid electrolyte materials such as zirconia or titania to construct oxygen ion conduction channels. When nitrogen oxides in the exhaust gas react with the sensing unit, a weak current signal proportional to the concentration is generated. The control circuit amplifies, processes, and converts the signal into a standard CAN bus signal for output. The entire process can achieve a response time in the millisecond range. ‌

Its core structure comprises four major components:

Sensing unit: As the "heart", it is responsible for sensing the concentration of nitrogen oxides;

Heating unit: During cold start-up, quickly heat the sensing unit to an operating temperature of 600°C–800°C and maintain it stable;

Control circuit: Processes raw signals and facilitates communication with the ECU;

Protective shell: Made of special alloy material, it can withstand extreme environments ranging from -40℃ to 900℃, while also resisting chemical corrosion and electromagnetic interference. ‌

Function and application: NOx sensors play three major roles in emission control:

Emission control: By monitoring NOx concentration in real-time, we provide data support for the Selective Catalytic Reduction (SCR) system, precisely regulating the urea injection quantity to ensure a reduction of diesel vehicle NOx emissions by over 90%, meeting stringent standards such as China VI;

System optimization: Collaborate with ECU to dynamically adjust engine parameters (such as ignition timing, air-fuel ratio), improve combustion efficiency while ensuring emissions meet standards, and optimize urea and fuel consumption;

Fault warning: Equipped with a built-in self-diagnostic function, it continuously monitors its own status. In case of any abnormalities, it can trigger an alarm via the CAN bus to prevent excessive emissions or performance degradation. ‌

This sensor is primarily utilized in diesel exhaust gas treatment systems compliant with the China VI emission standard. A typical setup involves installing dual sensors before the DOC (diesel oxidation catalyst) and after the SCR (selective catalytic reduction), enabling closed-loop control through concentration comparison. This optimizes urea usage and ensures stable emissions. ‌

Technical Challenges and Testing: Due to long-term operation in high-temperature and corrosive environments, the design lifespan of sensors is typically 6,000 hours, and aging may lead to inaccurate SCR control. The testing phase needs to address the challenge of synchronous multi-signal acquisition, such as expanding the number of channels through cascaded oscilloscopes to simultaneously monitor NOx concentration signals, heater voltage signals, and ECU communication signals, in order to verify the reliability of sensors under extreme operating conditions such as cold start and anti-interference.

SYHOWER is one of leading suppliers in China, specializing in the production of Mercedes Benz engine, Mercedes Benz chassis, SCANIA engine, etc. We have been engaged in the European truck parts industry since 2000 and have a history of more than 20 years. With the continuous growth of the company, it has won the recognition of domestic and foreign customers with excellent professional skills and strong technical strength. The business scope of Shenzhen Xinhaowei Industry and Trade Development Co., Ltd. is international import and export trade, domestic material supply and marketing. Mainly engaged in imported parts of European trucks (commercial vehicles), heavy-duty special vehicles, and buses. It is the exclusive agent and designated distributor of many well-known parts manufacturers in China. At present, it has developed into a major supplier of European auto parts in China. The parts we distribute mainly include the following models: MAN, NEOPLAN, BENZ, VOLVO, KASSBOHRER, BOVA, SCANIA and other auto parts and OEM parts. Since the establishment of our company, every step of development has followed the first-class business philosophy, and treated customers with a professional and serious attitude. The company has always been committed to the pursuit of high-quality, low-price products. We have an absolute product price advantage and perfect service quality, in order to achieve perfection. We support MOQ. We are willing to let customers know us first, grow together, and win-win cooperation!