Research on CO2 concentration detection technology based on tunable diode laser absorption spectroscopy

In the observation of CO₂ flux, high-speed and high-precision measurement of CO₂ concentration is an urgent problem to be solved, and the collection frequency of CO₂ concentration must be greater than 10Hz. The Tunable Diode Laser Absorption Spectroscopy (TDLAS) technology is widely used in various gas monitoring fields with high requirements for sensitivity, response time, and no background gas interference. In this paper, interband cascade laser at 4.26 micron is used as the system light source, and the second harmonic peak-peak value and the Root Mean Square (RMS) of sinusoidal are used to measure the CO₂ concentration. When the laser CO₂ analyzer was developed, comparative experiments were conducted using LI-7500DS and self-developed equipment. The CO₂ concentration values measured by the laser gas analyzer and the LI-7500DS gas analyzer are synchronously collected using a sampling frequency of 10 Hz. The experimental results show that the trend of CO₂ concentration measured by the two devices is consistent, and deviation of CO₂ concentration is within ±2%, which can meet the needs of carbon dioxide flux measurement.