Laser methane concentration measuring method based on double-spectrum absorption line and waveform matching

Abstract

The invention discloses a laser methane concentration measuring method based on double-spectrum absorption line and waveform matching. A semiconductor laser performs wavelength linear scanning and covering on two specified absorption lines, laser passing through a gas to be measured is subjected to processing such as narrow-band band-pass filtering and high-speed acquisition by a receiving circuit and then subjected to waveform matching with a reference absorption line, various noises and interference removal and an actual absorption line retaining, and finally, real-time inversion of the concentration of the gas to be measured is carried out by adopting a double-spectrum absorption line concentration inversion algorithm. The laser methane concentration measuring method disclosed by the invention solves the contradiction widely existing in the conventional application of a laser absorption spectrum technology in gas concentration measurement that measurement range and minimum detection limit are difficult to consider, expands the concentration measurement range while ensuring the minimum detection limit of laser methane concentration measurement, solves the problem of concentration misinformation of a measuring system caused by optical and electrical interference, and ensures the measurement accuracy.

Description

technical field [0001] The present invention relates to tunable semiconductor laser absorption spectrum measurement technology in the field of laser spectroscopy, to signal modulation technology and weak signal processing method in laser spectrum signal processing, especially a laser methane concentration measurement based on dual-spectrum absorption lines and waveform matching method. Background technique [0002] Gas (main component: methane) outburst and explosion problems have become an important threat to coal mine safety. Strengthening the detection of gas-like dangerous gases has become the basic guarantee for the safety of the modern coal mine industry. [0003] Gas detection using gas molecular laser absorption spectroscopy has the characteristics of high precision, fast response, strong resistance to gas interference and non-contact measurement, and has become a key development technology for modern gas detection. Compared with the currently commonly used catalyti...

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Problems solved by technology

[0006] (1) Since the measuring optical path is exposed to the gas environment to be measured, the receiving photodetector is easily interfered by various ambient lights;

[0007] (2) The laser light returning to the photodetector through the reflection or scattering path is often very weak, and the electrical noise in the photoelectric detection amplifier circuit has a great influence on the signal-to-noise ratio of the spectral absorption waveform;

[0008] (3) In some measurement environments, the background of the reflected laser light will change during the measurement process, and the signal mutation will also interfere with the absorption waveform

[0009] Once these situations happen, the interference will change or even overwhelm the actual gas absorption signal, which will affect the accuracy of the measurement results and cause false alarms in some systems that require gas concentration alarms.

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