差分式中红外一氧化碳检测仪的研制

根据CO分子在中红外波段的吸收特性,利用红外热辐射光源(IR55)和双通道热释电探测器(LM244),研制了一种差分式CO检测仪。通过双通道锁相放大器对探测器输出的两路信号进行处理,有效地抑制了系统噪声,提高了仪器的检测精度。介绍了系统的检测原理,给出了光学系统和双通道锁相放大器的实现方案,该锁相放大器能提取的最小标准信号幅度为1 m V,移相误差小于0.2%。利用配备的体积分数为0~1×10~(-3)的CO样品,开展了气体检测实验。实验结果表明:系统的检测下限为1×10~(-5),相对测量误差小于15%。当气体体积分数为0×10~(-6)时,测得浓度的波动范围为-5.2×10~(-6)~6.2×10~(-6)。考虑静态配气时气体在气室中扩散的时间,仪器的响应时间约为58~62 s。同基于量子级联激光器和分布反馈激光器的CO检测仪相比,所研制的仪器具有结构简单、性价比高等优势,在煤矿、环保等场合的CO检测方面具有较好的应用前景。

Development of a differential mid infrared carbon monoxide detection device

According to the absorption characteristic of carbon monoxide molecular in mid infrared waveband, a dual channel (i.e. detection signal channel and reference channel) differential carbon monoxide (CO) detection device is developed using an infrared thermal radiation light source (IR55) and dual channel pyroelectric detector (LM244).A dual channel lock in amplifier is used to process the two output signals of the dual channel detector, the system noise is restrained effectively and the detection precision of the instrument is enhanced. The detection principle of the system is introduced,the implementation scheme of the optical system and the dual channel lock in amplifier is given.The amplitude of the minimum standard signal that the dual channel lock in amplifier can extract is 1 mV, and the phase shift error is below 0.2%. Using the prepared CO samples with the volume fraction of 0~1×10 3, the gas detection experiments were carried out to test the device performance. Experiment results show that the low detection limit of the system is about 1×10 5, and the relative measurement error is less than 15%. The concentration variation range is -5.2×10-6~6.2×10-6 when the gas volume fraction is 0×10-6. Considering the gas diffusion time in the gas cell during static gas preparation, the response time of the instrument is about 58~62 s. Compared with the CO detection instruments utilizing quantum cascaded lasers and distributed feedback lasers, the developed instrument has the advantages of simple optical path structure, high performance cost ratio and etc., and has broad application prospects in CO detection under the circumstances of coal mine, environment protection and etc.