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Aluminium Oxide Moisture Sensor

The aluminium oxide (AL2O3) moisture sensor provides accurate determination of dew point, ppm, or relative humidity in most industrial gases.

The aluminium oxide sensor is, by function, a capacitor. The sensor is capable of measuring ppm and dew point measurements in most industrial gas streams. The electronics are mounted internally and process the signal from the sensor and display the readings on the front display panel.

Aluminium Oxide Sensor Theory

An aluminium probe is chemically treated to form a thin porous coating of aluminium oxide. The aluminium oxide is then coated with a thin, permeable layer of gold. The gold layer and the aluminium probe form the anode and cathode.

Cross-section of aluminium oxide sensor probe.

The gold layer is permeable to moisture and conductive. This forms the second electrode of a capacitor.

The pores in the aluminium oxide layer absorb moisture from the gas stream in amounts directly proportional to the moisture content of the gas stream.

How the aluminium oxide sensor probe detects moisture.

The absorption of water molecules changes the capacitance of the sensor. The capacitance of the sensor is measured which is then converted to the moisture value.

The radius of the pores in the aluminium oxide layer make the sensor specific to water molecules.

Uses of the Aluminium Oxide Sensor

The aluminium oxide sensor is suitable for use on virtually any application where moisture measurements are required.

Industrial applications for moisture analyzers fall into two areas:

  • Gas Producers: for ensuring product quality
  • Gas Users: to ensure reliability of inert gas blankets.

Typical industries requiring the use of moisture measurement equipment are Semiconductor, Metal Treatment, and Plastics.

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