Search query: gas concentration detection contactless laser

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abstract: As motor vehicle exhaust emission causes more and more serious pollution in recent years, the natural environment and human health are facing great threats. It is of great significance to accurately measure the concentration of carbon monoxide, as one of the main pollutants of vehicle exhaust emissions. The detection system based on tunable diode laser absorption spectroscopy (TDLAS) is featured by high resolution, high sensitivity and fast response. Besides, TDLAS can eliminate the interference of the remaining gas by using tunable and narrow linewidth characteristics of semiconductor lasers, and selecting the single absorption line of specific gas, and finally realize the gas concentration inversion of high precision. Based on TDLAS, the motor vehicle exhaust component CO concentration detection system was designed and realized by using DFB laser with the center wavelength of 2330nm and selecting the absorption lines of CO gas at 2333nm. The hardware composition and software design of the system were introduced. In the experiment, motor vehicle exhaust of different vehicles was collected, and spectrum data obtained through the system components were used for CO concentration inversion. To improve the signal to noise ratio of the system and reduce the detection limit of the system, the balance detection technology was used in the system. Experiments show that the system has excellent stability, and can ensure accurate inversion of concentration results, and meet the real time on line detection of vehicle exhaust CO concentration.
author_names: Yi-bing Lu

Wenqing Liu

Yujun Zhang

Kai Zhang

Dongqi Yu
title: The design of motor vehicle exhaust carbon monoxide concentration detection system based on tunable diode laser absorption spectroscopy
venue: International Symposium on Advanced Optical Manufacturing and Testing Technologies (AOMATT)
year: 2019

abstract: Abstract A highly sensitive low concentration gas sensor based on dual wavelength Erbium doped fiber ring laser (EDFRL) is designed and demonstrated. The dual wavelength lasing output is introduced by a tunable Fabry Perot (F P) filter and a fiber Bragg grating (FBG) due to the mode competition as they both share a same EDF gain medium. One wavelength at 1530.37 nm serving as the sensing element is inserted by a hollow core photonic crystal fiber (HCPCF) gas cell which can bring in much more power change when the cavity loss slightly varies while the other wavelength at 1532.38 nm acting as a reference. Experimental results show that the sensor can achieve a good linear response (R2 0.9864) to acetylene concentration variation and a minimum detection limit (MDL) of 10.42 ppmV at 20 s response time, which is the lowest to our best knowledge and improving 6.44 times than that of single wavelength EDFRL based. Moreover, the absolute detected error induced by the power fluctuation
author_names: Xianchao Yang

Liangcheng Duan

Haiwei Zhang

Ying Lu

Guangyao Wang

Jianquan Yao
title: Highly sensitive dual wavelength fiber ring laser sensor for the low concentration gas detection
venue: Sensors and Actuators B: Chemical
year: 2019

abstract: Seven common optical methods for gas concentration detection are described. The basic principles, advantages and disadvantages of each method are given in detail. The improvement work and some novel ideas are presented. The applications of combined methods are discussed. These optical methods include some con ventional gas concentration detection technologies, such as optical interferential method, photoacoustic detection (PAS) correlation spectroscopy, and some novel gas concentration detection technologies, such as tunable diode laser absorption spectroscopy (TDLAS) evanescent wave field sensing technology, hollow core photonic bandgap fiber (HC PBF) sensing technology and fiber loop ring down spectroscopy (FLRDS) The prospect of optical gas sensing is listed at the end of the paper, which mainly refers to miniaturization, intelligence, portability, low power consumption, high accuracy, fast response and distributed multi component telemetry technology.
author_names: Shutao Wang

Changbing Wang

Zhao Pan

Deming Kong

Qi Cheng

Zhifang Wang
title: Applications of optical technology in gas concentration detection
year: 2017

abstract: The invention relates to an optic travelling wave cavity enhanced laser raman gas concentration detection device. The device combines a cavity enhanced technology with a laser raman detection technology, and utilizes an optic traveling wave passive cavity; a single curved surface annular internal reflector forms a high fineness cavity, and a laser outgoing beam oblique incidence cavity enhanced principle is utilized, so that laser beam is reflected in the cavity for many times and is propagated in a travelling wave manner, the laser beam passes through gas to be detected in an area to generate raman scattering, raman scattered light is collected by a photoelectric detection component after being gathered with the laser beam through a filter plate, and the photoelectric detection component detects the raman frequency shift and the corresponding raman peak intensity of the characteristics of the gas to be detected to obtain the concentration of the gas to be detected. The detection device disclosed by the invention has the characteristics of simple structure, low requirements on mechanical location, good stability and high reliability; meanwhile, the anti jamming performance of the detection device is improved; the detection device can measure on line in real time to increase the dynamic information of the process and can detect the concentration of nearly all gas, except inert gas; the sensitivity is high; the response speed is high and the response time is short.
title: Optic travelling wave cavity enhanced laser raman gas concentration detection device
year: 2014

abstract: The relationship between absorption and gas concentration was studied using a diffuse integrating cavity as a gas cell. The light transmission process in an arbitrary diffuse cavity was theoretically derived based on a beam reflection analysis. It was found that a weak absorption condition must be satisfied to ensure a linear relationship between absorbance and gas concentration. When the weak absorption condition is not satisfied, a non linear relation will be observed. A 35 x 35 x 35 cm diffuse integrating cavity was used in the experiment. Different oxygen concentrations were measured by detecting the P9 absorption line at 763.8 nm, based on tunable diode laser absorption spectroscopy. The relationship between the absorption signals and oxygen concentration was linear at low oxygen concentrations and became non linear when oxygen concentrations were higher than 21% The absorbance value of this transition point was 0.17, which was considered as the weak absorption condition for this system. This work studied the theoretical reason for the non linear phenomenon and provided an experimental method to determine the transition point when using a diffuse integrating cavity as a gas cell.
author_names: Xue Zhou

Jia Yu

Lin Wang

Zhiguo Zhang
title: Investigating the Relation between Absorption and Gas Concentration in Gas Detection Using a Diffuse Integrating Cavity
year: 2018

abstract: Online dissolved gas analysis (DGA) is an effective technique to obtain the health status information of insulation oil in power transformers. The typical hydrocarbon gases (methane, ethyne, ethene, ethane) decomposed from insulation oil, are the key indicators to diagnose the fault type and severity. To realize contactless and field measurement, a multi gas detection system based on tunable diode laser absorption spectrum (TDLAS) is proposed in this paper. Critical technique problems on the light source, long path gas cell, and the topology for multi gas detection are investigated. Individual central wavelengths of hydrocarbon gases are set at as 1653.72 nm for methane, 1530.37 nm for ethyne, 1620.04 nm for ethene and 1679.06 nm for ethane in the near infrared band. A 10.13 m long multi pass gas cell is developed with the advantage of anti vibration design. To share the optical absorption path, an optical switch is adopted to merge the multi gas detection system. The high sensitivity of the TDLAS multi gas detection system was demonstrated in the laboratory calibrations, with ethyne detection reaching sub parts per million level, and the other hydrocarbon gases achieving ppm level. Furthermore, the comparison detection in the real 220 kV power transformer gave evidence to the effective monitoring of DGA, proving it an alternative approach to online detection of multiple gases in power transformer oil.
author_names: Jun Jiang

Zhuowei Wang

Xiao Han

Chaohai Zhang

Guoming Ma

Chengrong Li

Ying-Ting Luo
title: Multi gas detection in power transformer oil based on tunable diode laser absorption spectrum
venue: IEEE Transactions on Dielectrics and Electrical Insulation
year: 2019

abstract: Tunable diode laser absorption spectroscopy (TDLAS) is a technique measuring the concentration of trace gas, the gas concentration is in the sub ppm (part per million) range. Experiment results show that the main part of system noise is interference fringes originating from multiple reflections between surfaces in optical components, so called etalon effects. This work investigates the basis principle of the measurement of trace gas concentration using wavelength modulation spectroscopy (WMS) technique and analyses etalon effects from different types of optical surfaces. Fluctuations in temperature or vibrations of the etalon cause the interference fringes to shift in wavelength, and the interference fringes originated from short etalons within laser or photodetector cannot be removed by subtraction of a zero baseline using wedged or dithered components. It is shown that although analytical signal, SAS,nf, for short etalons, is decreasing with increased detection order, the signal to background ratio (SAS/SBG)nf is improved significantly. It is more advantageous to detect higher even harmonic signals, e.g. the 4th or 6th, than 2nd to reduce or eliminate the interference fringes originated from short etalons within laser or photodetector.
author_names: Jia-nian Cao

Zhuo Wang

Ke-ke Zhang

Rui Yang

Yong Wang
title: Etalon Effects Analysis in Tunable Diode Laser Absorption Spectroscopy Gas Concentration Detection System Based on Wavelength Modulation Spectroscopy
venue: 2010 Symposium on Photonics and Optoelectronics
year: 2010

abstract: In order to improve the signal to noise ratio(SNR) and the detection limit of the tunable diode laser absorption spectroscopy(TDLAS) the system's second harmonic signal and noise are analyzed.Then four kinds of digital filtering techniques are used for comparison, and four corresponding software programs written by Visual C+ language are used for noise compression and signal extraction from the original noised second harmonic signal.Finally, the a b g filter and Kalman filter are used for denoising and data smoothing.The results show that the detecting limit is improved from 30 ppm to 5 ppm by introducing least square method and the SNR is enhanced to 8 times by using the Kalman filter.This method is applied to the TDLAS on line industrial gas monitoring system,and a good result can be obtained.
author_names: Wang Yu
title: Selection of digital filtering techniques in trace gas concentration detection with a tunable diode laser absorption spectroscopy
year: 2010

abstract: Abstract Gas line shape is determined by the Voigt profile, which is the convolution of Lorentz and Doppler profiles. The calculation amount in the Voigt profile is much larger than that in the two other profiles, and an approximate Lorentz or Doppler profile is generally used in gas concentration detection via tunable laser absorption spectroscopy. The normalized peak ratio and error function are introduced to compare the approximating effect of the two profiles. The normalized peak ratio value is simulated for Doppler profile and Lorentz profiles over a variable temperature and pressure, respectively. The 10% 5% and 2.5% error functions for pressure versus temperature are obtained for the two profiles. Oxygen at a wavelength of 760 nm is used to demonstrate the simulation results. The presented method of investigating line shapes can be applied to other gas spectrum lines.
author_names: Wenke Liang

Xiaozhou Dong

Yunfeng Bi

Tieliang Lv
title: Temperature and pressure dependence of the line shape at l 763 nm in oxygen concentration detection
year: 2019

abstract: The invention discloses a system and method for gas concentration detection based on a programmable amplifier. The system comprises a microprocessor, the microprocessor is connected with a current driving circuit, the current driving circuit is connected with a DFB laser, and the DFB laser is connected with an optical fiber coupler. The optical fiber coupler is used for dividing a light beam emitted by the DFB laser into first beam optical signals and second beam optical signals to respectively send the first beam optical signals and the second beam optical signals to a first photoelectric detector and an air chamber; the first photoelectric detector converts the received first beam optical signals into a reference voltage and then transmits the reference voltage to a first programmable amplifying circuit, the air chamber is connected with a second photoelectric detector, and the second photoelectric detector is used for receiving optical signals output from the air chamber, converting the optical signals into voltage signals and transmitting the voltage signals to a second programmable amplifier. The output end of the first programmable amplifier and the output end of the second programmable amplifier are connected with a first input end and a second input end of a differential circuit, the output end of the differential circuit is connected with the input end of a signal conditioning circuit, and the output end of the signal conditioning circuit is connected with a microprocessor.
title: System and method for gas concentration detection based on programmable amplifier
year: 2015