Fit dynamic peak searching method for detecting gas concentration by laser
A technology of concentration detection and laser gas, which is applied in the direction of color/spectral characteristic measurement, etc., can solve the problem of inaccurate locking of absorption peaks, etc., and achieve the effect of miniaturization, reduction of precision and system synchronization requirements, and system simplification
Active Publication Date: 2011-11-30
INST OF SEMICONDUCTORS - CHINESE ACAD OF SCI
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[0004] In view of this, the main purpose of the present invention is to provide a fitting dynamic peak-finding method for laser gas concentration detection, so as to improve the traditional feedback method through current scanning and back-end digital algorithm without increasing the complexity and cost of the system. The problem of inaccurate locking absorption peak in peak locking method
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[0028] In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be described in further detail below in conjunction with specific embodiments and with reference to the accompanying drawings.
[0029] The fitting dynamic peak-seeking measurement method of the present invention continuously applies a bias current to the laser periodically and linearly, without adding a modulation signal, and the closed-loop control locks the output wavelength of the laser; without adding a reference straight line, the laser can be obtained working in the gas to be measured The full spectrum of the photocurrent detected near the wavelength of the absorption spectrum, by processing the photocurrent data and using mathematical processing, a reference curve is fitted, and the gas concentration data is obtained through analysis. That is to say, a new method of dynamic peak-finding for laser gas concentration detection is provided.
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The invention discloses a fit dynamic peak searching method for detecting gas concentration by laser, which comprises that: a controller adjusts the working temperature of a wavelength specific laser to a certain proper value, linearly increases bias current for the wavelength specific laser, and simultaneously receives current signals transmitted by a photoelectric detector to obtain a photocurrent primitive curve; the controller judges whether an absorption peak is in the middle of the photocurrent primitive curve, if the absorption peak is not in the middle of the curve, the temperature adjustment is continued, otherwise, the photocurrent primitive curve is subjected to secondary differential analysis to form a secondary differential curve, and proper fit points are selected to fit a reference curve; and the controller compares the reference curve with the primitive curve to obtain a normalized absorption peak curve, and the gas concentration is obtained by calculating the maximum of the normalized absorption peak curve. Through the method, the position of the absorption peak of the gas to be tested can be dynamically found in real time, and the method for searching the absorption peak has the advantages of strong real-time and accurate peak searching. The normalized absorption peak curve obtained by secondary differential analysis and curve fit eliminates the influence of system noise and wavelength slow drift, and the concentration of the gas to be tested deduced by the normalized absorption peak curve is more accurate.
Description
technical field [0001] The invention relates to the technical fields of optical fiber sensing, optoelectronics, and spectroscopy, and in particular to a fitting dynamic peak-finding method for laser gas concentration detection, which is applied to harmful gas detection, atmospheric humidity detection, and all other fields applied to gas concentration detection . Background technique [0002] In the field of gas sensing and gas concentration measurement, wavelength tunable laser spectral absorption method is a newly developed method to measure gas concentration. The high-precision gas concentration sensor based on laser fiber optic sensing has the advantages of fast response speed, high measurement accuracy, and little damage to gas components. However, this method requires that the working wavelength of the laser or the wavelength of the test point be strictly locked on the absorption line of the gas to be tested, so as to ensure the accuracy of the test results. There are...
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IPC IPC(8): G01N21/39
Inventor 孙可谢亮鞠昱
Owner INST OF SEMICONDUCTORS - CHINESE ACAD OF SCI