To enhance the detection limitation and sensitivity of carbon monoxide , a trace CO detector is devel-oped.The detector uses a mid -infrared (MIR) quantum cascade laser with centre wavelength at 4.8 m combi-ning MIR multipass herroitt cell with 76 m absorption path length , is capable of improving the detection limita-tion and sensitivity of carbon monoxide .Meanwhile , an optical structure with dual differential channel paths is integrated to eliminate the instability induced by electrically modulated light source .The experimental results show that the proposed instrument can be applied into in -situ sensitive , rapid and continuous measurements of trace carbon monoxide , with low detection sensitivity down to 40 nmol/mol level in 4 s acquisition time .In ad-dition, operator could substitute a QCL operating at a different wavelength to measure other gases .%为了提高一氧化碳（ CO）气体浓度的检测下限和灵敏度，研制了一种痕量CO检测仪。该检测仪采用激发波长为4．8μm的中红外量子级联激光器（QCL），结合中红外光程长度为76 m的多次反射herriott吸收气室，有效地提高了CO气体浓度检测下限和灵敏度。同时，利用差分双光路空间光学结构，消除了电调制光源所带来的不稳定性。实验表明，该检测仪能够灵敏、快速和连续地检测环境空气中痕量CO气体浓度，在4 s的采样时间内达到了40 nmol／mol 气体检测灵敏度，也可通过替换在不同波长下运行的QCL测量其它气体。
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