Aluminum oxide moisture sensor

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. 

Figure 7. Schematic cross sections of (a) conventional aluminum oxide moisture sensor, and (b) CFT aluminum oxide moisture sensor.

Figure 9. Sheet resistance data illustrating the effect of aging on aluminum oxide moisture sensor. Reproduced with permission from reference 18. Copyright 1982 Institute of Electrical and Electronics Engineers.

Aluminum oxide charge-flow transistor, transfer function, 171,173,174f Aluminum oxide moisture sensor aging effects, 174f charge-flow transistor, 172f hysteresis effects, 175f... 

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... 

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. 

Oxide Sensors Aluminum oxide can be used as a sensor for moisture analysis. A conductivity call has one electrode node of aluminum,... 

This test method covers the determination of the water vapor content of gaseous fuels by the use of electronic moisture analyzers. Such analyzers commonly use sensing cells based on phosphorus pentoxide, P2OS, aluminum oxide, AI2O3, or silicon sensors. 

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