基于红外波段光谱吸收的小型化湿度探测系统

 探测系统的光源选择为垂直腔面发射激光器，选定水汽在1.854 μm的吸收峰。系统自动在直接测量法与谐波测量法之间切换，能够适应高低湿度环境。在低湿度环境检测中，利用二次谐波与一次谐波的比值来定标湿度，有效去除了光源不稳定对测量带来的影响；过采样的A/D转换结合数字锁相放大（DLIA）技术，提高了检测精度。系统通过以太网接口，可以实现远程数据采集。

Undersized humidity detecting system based on infrared spectrum absorption

An undersized humidity detecting system based on infrared spectrum absorption is introduced. A vertical-cavity surface-emitting laser is used as the light source and provides lasers at 1.854 μm which is a main absorption peak of water vapor. To cover all humidity condition, vapor density is detected via two different methods, which are switched by the system automatically depending on measure results. In low-density condition, the ratio of the second-harmonic to fundamental signal is used to eliminate the interference due to light power variation. A/D conversion with over-sampling and digital lock in amplification enhance the accuracy of signal processing, and with IEEE 802.11x protocol, automatic remote data acquisition is achieved.