High-precision detection technology of NO concentration based on UV differential-adaptive interference cancellation

In order to realize high-precision monitoring of vehicle emission, a high-precision and wide-range NO measurement method was proposed. Aiming at the problem that the absorption peaks of SO2 and NO in emission overlapping in the UV band, and it was impossible to directly perform single-component gas inversion, the differential optical density (DOD) of mixed gas in the NO sensitive band (200 nm～230 nm) was first calculated by the ultraviolet differential optical absorption spectroscopy (UV-DOAS) method. Then, the adaptive interference cancellation technology was introduced to achieve rapid separation of mixed gas DOD. Finally, the least square method was used to perform the concentration inversion of separated NO. This method could achieve rapid inversion of NO concentration (volume fraction of gas) in the range of 100×10⁻⁶ to 3 000×10⁻⁶. After testing, the absolute value of the relative error of inversion is less than 10% in the concentration range of 100×10⁻⁶ to 200×10⁻⁶, and less than 5% in the concentration range of 300×10⁻⁶ to 3 000×10⁻⁶. This method has the characteristics of large measurement range and fast speed, and can meet the measurement requirements of NO concentration in the range of 3 000×10⁻⁶ in vehicle emission.