Near-infrared measurement of relative and absolute humidity through detection of water adsorbed on a silica gel layer.
Near-infrared measurement of relative and absolute humidity through detection of water adsorbed on a silica gel layer.
复制标题
通过检测硅胶层上吸附的水份来近红外测量相对湿度和绝对湿度。
DOI：
10.1021/ac00102a019
复制
发表时间：
1995
影响因子：
7.4
通讯作者：
Hieftje,GM
中科院分区：
文献类型：
--
作者：
Fong,A;Hieftje,GM
近红外光谱特别适合于水分的测定，因为与大多数其他物质相比，水的吸收率相对较高。本文将近红外漫反射光谱技术应用于高性能薄层硅胶板上吸附水分的测量。通过水分子对辐射的普通吸收和硅胶吸附更多水时增加的近红外辐射散射来检测被吸附的水。这项技术有望成为一种时间常数不到1分钟的高精度和灵敏的湿度传感器。在硅胶层中加入无机盐可以增加对水蒸气的响应。然而，它也增加了传感器的时间常数。文中还展示了一种使用商用近红外传输开关的微型湿度传感器。对可能的干扰和滞后效应进行了研究，传统的相对湿度(RH)和绝对湿度(AH)测量方法比较繁琐。最终的标准是将测量到的空气体积通过完美的干燥剂，并测量其质量变化。另一种标准方法是测量以特定速度流动的气流中湿球温度计和干球温度计的温度。也可以使用光学冷凝镜露点探测器。不幸的是，在这种标准方法不方便或不可能使用的情况下，经常需要湿度传感器。
Near-IR spectroscopy is especially well suited to moisture determination because of the relatively high absorptivity of water compared to most other substances. In the present work, near-IR diffuse-transmittance spectroscopy is applied to the measurement of humidity via observation of adsorbed water on a high-performance thin-layer chro-matography silica gel plate. The adsorbed water is detected through both ordinary absorption of radiation by water molecules and the increased scattering of near-IR radiation by the silica gel as it adsorbs more water. This technique shows promise as a highly accurate and sensi-tive humidity sensor with a time constant of less than 1 min. The addition of inorganicsalts to the silica gel layer is shown to increase the response to water vapor. How-ever, it also increases the time constant of the sensor. A miniature humidity sensor using a commercially available near-IR transmissive switch is also demonstrated. Pos-sible interferences and hysteresis effects are investigated.Conventional methods for the accurate measurement of relative humidity (RH) and absolute humidity (AH) can be cumbersome. The ultimate standard is to pass a measured volume of air through a perfect desiccant and to measure its mass change. Another standard method is to measure the temperatures of wet-bulb and dry-bulb thermometers in a stream of air flowing at a specific velocity. Optical chilled-mirror dewpoint detectors can also be used. Unfortunately, humidity sensors are often needed in situations where such standard methods are inconvenient or impossible to employ.