A ‌nitrogen oxide (NOₓ) sensor‌ is primarily used to detect the concentration of nitrogen oxides in gas, and its specific functions vary slightly by application scenario:

1. Automotive application (the most common scenario)

This type is mostly used in diesel vehicles (and some gasoline vehicles with exhaust treatment systems), and is a core component to meet emission regulations:

• ‌Real-time detection‌: It accurately measures the content of various nitrogen oxides (such as N₂O, NO, NO₂) in engine exhaust, and transmits the concentration data to the vehicle ECU (on-board computer) in real time.
• ‌Control SCR system‌: For vehicles equipped with a selective catalytic reduction (SCR) system, the ECU adjusts the urea injection volume based on the sensor data: increase the injection volume when the NOₓ concentration is too high, and reduce it when the concentration is up to standard, which can not only ensure the NOₓ purification efficiency but also avoid urea waste.
• ‌Emission compliance & fault early warning‌: It monitors whether the exhaust emission meets the legal standards, and triggers an alarm or enters the vehicle protection mode (such as limp mode) when the emission exceeds the standard or the sensor fails, which avoids penalties for excessive emission and prevents secondary damage to the exhaust system.
• ‌Optimize engine performance‌: The ECU adjusts the air-fuel ratio and ignition timing according to the feedback data, so as to improve combustion efficiency and fuel economy.

2. Industrial & environmental monitoring application

In fixed scenarios such as industrial emission outlets, atmospheric monitoring stations and chemical parks, the nitrogen oxide sensor module is used for:

• 24-hour continuous monitoring of NOₓ concentration in the ambient air or industrial exhaust, and upload the data to the environmental protection monitoring platform, and give an early warning when the standard is exceeded.
• Provide data support for enterprise emission compliance, regional air quality analysis and pollution prevention and control decision-making.