非合作目标TDLAS室内二氧化碳遥测

Standoff detection of indoor CO using TDLAS with non-cooperative targets

CO2浓度是室内空气质量的重要指标之一,室内CO2浓度监测对人体健康和节能减排有重要意义。为实现方便灵活的室内CO2高灵敏度遥测,基于可调谐二极管激光吸收光谱技术,研制了单端式非合作目标遥测系统,通过接收对面实际障碍物的后向散射光,用于室内CO2浓度的实时测量。通过直流信号归一化波长调制光谱二次谐波信号方法,消除光强变化的影响;利用此信号的过零点间距与谱线压力加宽的关系,校正开放光路中压强变化对浓度测量的影响。以室内墙面为非合作目标对室内CO2浓度进行了测量,结果表明该系统在积分时间5 s时灵敏度1.3×10-6 m,精度2.2×10-6,输出波动12×10-6,单程探测距离可达1.29 m。该系统可用于室内或机舱等密闭空间的CO2浓度监测。

The carbon dioxide concentration is one of the important indicators for evaluating the indoor air quality.Its monitoring is of great significance to human health,energy conservation and emission reduction.To realize convenient and flexible standoff detection for indoor CO2 with a high sensitivity,a single-ended laser sensing system with non-cooperative targets is developed,which is based on the tunable diode laser absorption spectroscopy(TDLAS)technology.It receives backscattered light from actual obstacles on the opposite side.To eliminate the influence of light intensity variation,a method of normalizing the wavelength modulation spectroscopy with second harmonic signal detection(WMS-2 f)by the direct signal is proposed.The effect of pressure fluctuation on the measured CO2 concentration is corrected by utilizing the relationship between its two zero-crossing spacing and the spectral line broadening.The indoor CO2 concentration is measured with the indoor wall as a non-cooperative target.Experimental results show that the detection sensitivity is 1.3×10-6 m at an integration time of 5 s with a precision of 2.2×10-6,and the output fluctuation of 12×10-6.The one-way detection distances can reach 1.29 m.The TDLAS system can be used for CO2 concentration monitoring in enclosed space,such as indoor room,aircraft cabin and so on.