Development Of Instrument For Oxygen Detection Based On TDLAS And Nonlinear Tuning Research

Oxygen (O2) is an important component of the atmosphere, and also importantgas in industrial production process and medical instruments. Detection of oxygenconcentration plays an important role in environmental monitoring, industrial processcontrol etc. Especially in the industrial production, oxygen is an important supportingmaterial combustion, and the oxygen concentration can be adjusted to reducepollutant emissions and effectively reduce environmental pollution. Furthermore,when the oxygen concentration in the combustion reaches risk range, it will cause anexplosion accident, causing major life safety and property loss.Oxygen concentration detection based on tunable diode laser absorptionspectroscopy (TDLAS) technique has advantages of non-contact, high sensitivity,strong selectivity, fast response, and the system has the advantages of simple structure,low cost, suitable for application in industrial production, medical instrument andaerospace fields. In this paper, aimed at detecting oxygen concentration, starting fromthe basic principle of tuning laser absorption spectroscopy, the principle of TDLASmeasurement system and oxygen absorption spectra have been studied. The laser lightsource, optical path and the gas path system have been optimally designed, andstarting from different measurement environment, several different forms of gasabsorption cell device were the mainly focuses on the design. The detection andreceiving units and other parts have been designed and improved, and then thereal-time measuring instrument for oxygen concentration measurement was developed.The instrument was tested from different angles, and the experimental results showthat the instrument has high sensitivity, stability and repeatability.The nonlinear tuning technique has been analyzed and compared with the lineartuning technology. Two nonlinear tuning methods were designed and implied, and thestability of measuring signal was analyze. The signal obtained by different tuningmethods were curve fitted and compared, and the results verify the nonlinear tuningmethod can effectively improve the signal sensitivity in curve fitting. Then thedifferent tuning methods are compared using Allan variance, and it further verifies theadvantage of nonlinear tuning technology compared with the traditional linear tuningmethod.