Aluminum Oxide

Aluminum Oxide (Al2O3) sensors are used to monitor moisture levels and dew point, and work by measuring the capacitance between the aluminum core and a gold film deposited on top of the oxide layer.

The capacitance varies with the water vapor content contained in the pores of the oxide layer, and is inversely proportional to the distance between the capacitor plates. Servomex’s aluminum oxide sensors have three innovative structural improvements giving them a strong advantage over traditional Al2O3 sensors and providing industry-leading sensitivity and stability.

A much thinner oxide layer produces much higher capacitance changes, reducing the impact of drift due to undesirable factors. This also means water moves in and out of the pores more quickly, producing a faster response.

A better-defined barrier layer between the aluminum and the aluminum oxide reduces metal migration, which is one of the major causes of aging drift in conventional sensors.

The unique, stable pore geometry of the Al2O3 sensor enhances the entrapment of water molecules, increasing the change in capacitance for a given change in dew point, which in turn provides more accurate results, and a quicker response.

The pore geometry in conventional sensors collapses slowly over time, requiring frequent recalibration. The Servomex Al2O3 sensor’s pore geometry does not change significantly, so it needs only an annual calibration check when used in clean, non-corrosive gases.

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