Moisture measurement oxide sensors

The aluminum oxide sensor is also used for moisture measurements in liquids (hydrocarbons). Because ot us low power usage, it is suitable lor use in explosion prool installations. These sensors are frequently used in petrochemical applications where low dew points are to he monitored on line and where the reduced accuracies and other limitations are acceptable. The advantages of the sensor must be weighted against the fact that... 

Yamazoe N, Suematsu K, Shimanoe K (2012) Extension of receptor function theory to include two types of adsorbed oxygen for oxide semiconductor gas sensors. Sens Actuators B 163 128-135 Yeo TL, Sun T, Grattan KTV (2008) Fibre-optic sensor technologies for humidity and moisture measurement. Sens Actuators A 144 280-295... 

Aluminum Oxide Moisture Sensor. This type of sensor is a capacitor, formed by depositing a layer of porous aluminum oxide onto a conductive substrate, and then coaling the oxide with a thin film of gold The conductive base and the gold layer become the capacitor s electrodes. Water vapor penetrates the gold layer and is absorbed by the porous oxidation layer The number of water molecules absorbed determines the electrical impedance of the capacity, which is. m turn, a measure of water vapor pressure. 

Sensing chemical species is a much more difficult task than the measurement of mechanical variables such as pressure, temperature, and flow, because in addition to requirements of accuracy, stability, and sensitivity, there is the requirement of specificity. In the search for chemically-specific interactions that an serve as the basis for a chemical sensor, investigators should be aware of a variety of possible sensor structures and transduction principles. This paper adresses one such structure, the charge-flow transistor, and its associated transductive principle, measurement of electrical surface impedance. The basic device and measurement are explained, and are then illustrated with data from moisture sensors based on thin films of hydrated aluminum oxide. Application of the technique to other sensing problems is discussed. 

Clayton W A 1993 Improved capacitive moisture sensors Sensors 10 16-22 Ishihara T et al 1991 Application of mixed oxide capacitor to the selective carbon dioxide sensor. I. Measurement of carbon dioxide sensing characteristics J. Electrochem. Soc. 138 173-6... 

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