利用石英音叉增强型光谱技术（QEPAS）结合基于Lab—VIEW设计的数字频率锁定技术建立了一套气体实时探测系统，该方案使用3f信号作为误差反馈信号，将激光器锁定在待测气体吸收峰的中心位置，保证了长时间测量的准确度并且提高了探测效率．实验中采用中心波长位于1．396μm的DFB半导体激光器作为光源，选择常压下空气中的水汽作为研究对象，对系统性能进行了测试，并对影响影响系统探测灵敏度的主要因素进行了分析．实验结果表明，该系统可以将激光器稳定在士0．001cm-l范围内，对激光器长时间工作时的波长漂移起到了很好的抑制作用，系统的检测限约为1 ppm，该方案可以直接应用于工业气监测、痕量污染物实时测量等领域．%A real-time measurement of gases based on QEPAS is introduced. For eliminating fluctuation of laser, a simple method, in which a digital PID algorithm and a software lock-in amplifier designed by using Lab-VIEW are employed, is utilized to lock the laser to the center of the absorption line. In order to test the system, an absorption line of water vapor near 1.396 ~m is chosen by using a fiber-coupled distributed feedback （DFB） diode laser. An over-40-hours continuous measurement is implemented, and the relevant results are presented and discussed. The detection limit of the system is 1 ppm. This method can also be used to measure the trace gases and monitor the industry gases.
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