Application of the Hygrometer (900-901D1) A-9
4/9/98
Aluminum Oxide Probe Maintenance
Other than periodic calibration checks, little or no routine
moisture probe maintenance is required. However, as discussed
in the previous section, any electrically conductive contaminant
trapped on the aluminum oxide sensor will cause inaccurate
moisture measurements. If such a situation develops, return of the
moisture probe to the factory for analysis and recalibration is
recommended. However, in an emergency, cleaning of the
moisture probe in accordance with the following procedure may
be attempted by a qualified technician or chemist.
IMPORTANT: Moisture probes must be handled carefully and
cannot be cleaned in any fluid which will attack
its components. The probe’s materials of
construction are Al, Al
2
O
3
, nichrome, gold,
stainless steel, glass and Viton
®
A. Also, the
sensor’s aluminum sheet is very fragile and can
be easily bent or distorted. Do not permit
anything to touch it!
The following items will be needed to properly complete the
moisture probe cleaning procedure:
• approximately 300 ml of reagent grade hexane or toluene
• approximately 300 ml of distilled (not deionized) water
• two glass containers to hold above liquids (metal containers
should not
be used).
To clean the moisture probe, complete the following steps:
1. Record the dew point of the ambient air.
2. Making sure not to touch the sensor, carefully remove the
protective shield from the sensor.
3. Soak the sensor in the distilled water for ten (10) minutes. Be
sure to avoid contact with the bottom and the walls of the
container!
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