Laser online oxygen analyzer

Laser online oxygen analyzerparameter

The modulated semiconductor laser absorption spectroscopy (TDLAS) technology utilizes the principle that laser energy is selectively absorbed by gas molecules to form an absorption spectrum for measuring gas concentration. Due to the emission of a specific wavelength laser beam by semiconductor lasers (which can only be absorbed by the measured gas), the attenuation of laser intensity when passing through the measured gas is a certain function of the concentration of the measured gas. Therefore, by measuring the attenuation information of laser intensity, the concentration of the measured gas can be analyzed and obtained.

When a laser with a light intensity of 𝑰𝟎 (ν (t)) passes through the detected gas, the gas will absorb the light. Different substances will absorb light of certain frequencies. When passing through an optical path of length L, the output light intensity I (ν (t)) can be expressed as follows:

The condition for the Lambert Beer law to hold is that the incident light has the characteristic of parallel monochromaticity, therefore lasers with good monochromaticity; The gas to be tested should be a homogeneous medium and should not scatter too much, causing the actual value to deviate from the theoretical value; The concentration of the substance to be tested cannot be too high, as a high concentration of the substance can also cause the actual value to deviate from the theoretical value.

There are only O2 absorption lines in the vicinity of 13100cm-1 (i.e. 763nm), and there is no interference from other absorption lines, which ensures that the experimentally measured absorption peak is the O2 absorption peak.