The structure and working principle of the ultraviolet absorption gas analyzer

The structure and working principle of the ultraviolet absorption gas analyzer

The ultraviolet absorption method is used to measure O3 gas because ozone (O3) absorbs ultraviolet radiation of specific wavelengths. Since the absorption band of O3 gas in the ultraviolet region is 253.7nm, this wavelength is used to measure its concentration.

The measurement principle of UV gas analyzer

Ultraviolet light of a specific wavelength (incident light) from the UV light source is introduced into the sample gas of the test chamber (gas cell) for O3 absorption. The amount absorbed is obtained by measuring the selective transmission of ultraviolet rays through a filter equipped with a photodetector. The concentration of O3 in the sample gas was calculated using the Lambert-Beer law measured by a photodetector.

The relationship between ultraviolet absorption and gas concentration is determined by Lambert-Beer's law

Lambert-Beer Law

The amount of incident light absorbed varies with the concentration of the absorbing molecules. This relationship is represented by Lambert-Beer's law.

Ι = Ι0exp (-μcd)

I: Intensity of transmitted light

Ι0: Incident light intensity

c: Absorption molecular concentration (component to be measured

μ : Absorption coefficient (a constant determined by the molecule and wavelength

d: Thickness of the absorption molecular layer (gas layer)

The structure and working principle of the ultraviolet absorption gas analyzer

An analyzer that uses UV is called a UV absorption gas analyzer. It has a simple structure, is easy to maintain, and features suitability for continuous measurement, thus being used for the measurement of O3.

When ultraviolet light (incident light) is continuously irradiated, the sample gas flows through the gas cell, and the absorption of ultraviolet light by O3 in the sample gas is directly proportional to the gas concentration. As the concentration of O3 increases, the absorption of ultraviolet rays in the gas cell also increases accordingly. The ultraviolet light absorbed in the gas cell is selected by the optical filter and transmitted to the detector. The transmitted light is detected by a photodetector (photodiode). Through signal processing of the detection signal, the concentration of O3 in the sample gas is continuously measured.