摘要:
Nowadays,the development trend of H2S concentration detection is real-time detection.The method based on spectral absorption principle is one of the development directions.The broadband light source was used to replace the high cost narrow band light source used in the past,so as to reduce the cost of the whole system and improve the practicability of the detection system.Narrow band light can be obtained by Bragg grating filtering for broad band light source.The light wave obtained by this method must be noise and fluctuate.So it was filtered to eliminate the noise and fluctuation of part of the system,and then the light beam splitter was used to make the difference between the detected optical path and the reference optical path.The dif-ferential signal not only eliminated part of the system noise and fluctuation,but also eliminated fundamental wave component. The useful signal value was relatively large,and the signal-to-noise ratio was increased.The second harmonic signal was deduced by mathematical analysis.The second harmonic was observed by SIMILINK simulation.Different concentrations of H2S gas would have different output signals,and the concentration of gas would be obtained.The advantages of the dual optical path difference method,harmonic detection technique and narrow band filtering technology were that the cost was reduced,the signal-to-noise ratio was increased,and the detection capability of the system was improved.The experimental results showed that it was feasible to detect H2S gas concentration by using the dual optical path difference method to extract harmonic signal on the basic of LED broad band light source.This method will reduce the system cost and provide the possibility for large-scale practical application.%H2S濃度檢測的發(fā)展趨勢是實(shí)時檢測,基于光譜吸收原則是其中一個發(fā)展方向.用寬帶光源替代以往使用的成本較高的窄帶光源,降低整個系統(tǒng)的成本,可以提高檢測系統(tǒng)的實(shí)用性.寬帶光源經(jīng)過Bragg光纖光柵濾波后可以得到窄帶光.此方法得到的光波必然會有噪聲和波動,然后對其進(jìn)行濾波,消除一部分系統(tǒng)的噪聲和波動,再通過光線分束器分別通入檢測光路和參考光路后做差.此差分信號不僅消除了一部分系統(tǒng)噪聲和波動,還消除了基波分量,增大了信噪比.用數(shù)學(xué)分析的方法推導(dǎo)出二次諧波信號,利用SI-MILINK仿真觀察此信號,不同濃度的H2S氣體會有不同的輸出信號,也就得到了氣體的濃度.雙光路差分法、諧波檢測技術(shù)和窄帶濾波技術(shù)綜合起來的優(yōu)勢是降低了成本,增加了信噪比,提高了系統(tǒng)的檢測能力.實(shí)驗仿真結(jié)果表明,在LED寬帶光源基礎(chǔ)上采用提取諧波信號的雙光路差分方法檢測 H2S氣體濃度正確可行,此方法降低了系統(tǒng)成本,為大范圍實(shí)際應(yīng)用提供了可能性.