A series double-chamber trace gas analysis system and gas concentration calculation method

Abstract

The invention provides a trace gas analysis system connected in series with two gas chambers. The system comprises a circuit module, an optical module and a gas circuit module; a laser driving circuit and a digital temperature control module are both connected to a laser; the laser is connected to a laser incidence interface on a standard gas chamber through optical fiber; a first laser emergence interface is connected to a second collimating convergence lens through the optical fiber; a second laser emergence interface is connected to a third collimating convergence lens through the optical fiber; a first photodiode detector is connected to a first pre-amplification circuit; a second photodiode detector is connected to a second pre-amplification circuit. According to the system, the influence of unstable factors such as laser wavelength drift and temperature pressure change on the gas analysis result in TDLAS technology is eliminated, and the system improves the fault tolerance rate of laser performance and environment-adapting ability.

Description

technical field [0001] The invention relates to a trace gas analysis system with double gas chambers in series and a gas concentration calculation method. Background technique [0002] Tunable Diode Laser Absorption Spectroscopy (TDLAS, Tunable Diode Laser Absorption Spectroscopy) is a technology widely used in the detection of trace gas concentration. It is widely used in petrochemical, environmental detection, biomedicine, aerospace and other fields, with selective Good, high precision, real-time non-contact and other advantages. TDLAS technology is based on the principle of molecular absorption spectroscopy. Due to the vibration form of different gas molecules, the molecules will absorb laser light of a specific wavelength. After the pool, the attenuation intensity of the outgoing light intensity is proportional to the gas concentration. In practical applications, the driving current of the laser increases the high-frequency sinusoidal modulation current to reduce the i...

AI Technical Summary

Problems solved by technology

[0003] Existing TDLAS systems often have only one analytical gas chamber, in which the gas to be measured is irradiated by laser light to form corresponding spectral signals, but because the properties of the gas itself are affected by temperature and pressure, the same concentration of gas at different temperatures The broadening and height of the absorption spectrum are different, so it is generally necessary to carry out constant temperature heat tracing treatment on the gas chamber, plus algorithms such as absorption line positioning and temperature correction to reduce the influence of unstable factors, and the tunable semiconductor (DFB) laser used in the system, There are high requirements for laser spectral line width, side mode suppression ratio and stability, and this kind of laser is relatively expensive

To sum up, the application of constant temperature system, precision components and correction algorithm will greatly increase the cost of equipment and increase the volume of equipment. More importantly, the determination of various correction parameters requires a large amount of calibration data accumulation, and the measurement concentration cannot be fully guaranteed in the long run. the accuracy of

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