基于中红外光谱吸收技术, 利用一氧化碳(CO)气体分子在4.6 μm处的基频吸收带, 采用新脉冲的红外光源和双通道的热释电探测器, 研制了一种CO浓度检测系统。 该系统主要由脉冲调制式宽带热光源、 开放式椭球聚光镜/气室、 双通道探测器、 主控及信号处理模块构成。 通过优化开放式椭球聚光镜/气室, 气体吸收光程达到40 cm, 探测器输出电信号的幅度增加约为原来的2~3倍。 因此, 采用椭球聚光镜后, 将在一定程度上提高系统的信噪比从而改善系统的性能指标。 利用配备的CO气体样品, 研究了该系统对CO气体的传感特性。 实验结果显示, 该系统的最小检测下限为10 ppm, 在该浓度点的测量误差约为14%; 在20~25 000 ppm范围内的测量误差小于7.8%; 对0 ppm气体样品的连续50分钟测量结果的最大偏差约为3 ppm, 标准差约为0.18 ppm。 同基于量子级联激光器和分布反馈激光器的CO检测系统相比, 该系统具有性价比高、 光路结构简单等优势, 从而在煤矿、 环保等场合下的CO检测方面具有较好应用前景。

Based on infrared spectral absorption technique, a carbon monoxide (CO) detection system was developed using the fundamental absorption band at the wavelength of 4.6 μm of CO molecule and adopting pulse-modulated wideband incandescence and dual-channel detector. The detection system consists of pulse-modulated wideband incandescence, open ellipsoid light-collector gas-cell, dual-channel detector, main-control and signal-processing module. By optimizing open ellipsoid light-collector gas-cell, the optical path of the gas absorption reaches 40 cm, and the amplitude of the electrical signal from the detector is 2 to 3 times larger than the original signal. Therefore, by using the ellipsoidal condenser, the signal-to-noise ratio of the system will be to some extent increased to improve performance of the system. With the prepared standard CO gas sample, sensing characteristics on CO gas were investigated. Experimental results reveal that, the limit of detection (LOD) is about 10 ppm; the relative error at the LOD point is less than 14%, and that is less than 7.8% within the low concentration range of 20~180 ppm; the maximum absolute error of 50 min long-term measurement concentration on the 0 ppm gas sample is about 3 ppm, and the standard deviation is as small as 0.18 ppm. Compared with the CO detection systems utilizing quantum cascaded lasers (QCLs) and distributed feedback lasers (DFBLs), the proposed sensor shows potential applications in CO detection under the circumstances of coal-mine and environmental protection, by virtue of high performance-cost ratio, simple optical-path structure, etc.