TH02 Datasheet, PDF (14/26 Pages) List of Unclassifed Manufacturers – D IGITAL I 2C H UMIDITY AND TEMPERATURE S ENSOR

TH02
2.8. Protecting the Sensor
Because the sensor operates on the principal of measuring a change in capacitance, any changes to the dielectric
constant of the polymer film will be detected as a change in relative humidity. Therefore, it is important to minimize
the probability of contaminants coming into contact with the sensor. Dust and other particles as well as liquids can
affect the RH reading. It is recommended that a filter cover is employed in the end system that blocks contaminants
but allows water vapor to pass through. Depending on the needs of the application, this can be as simple as plastic
or metallic gauze for basic protection against particulates or something more sophisticated such as a hydrophobic
membrane providing up to IP67 compliant protection.
TH02s may be ordered with a factory fitted, solder-resistant cover, which can be left in place for the lifetime of the
product. It is very low-profile, hydrophobic and oleophobic, and excludes particulates down to 0.35 microns in size.
SOrdering Guide” for a list of ordering part numbers that include the cover. A dimensioned drawing of the IC with
the cover is included in section. The sensor should be protected from direct sunlight to prevent heating
effects as well as possible material degradation.
2.9. Bake/Hydrate Procedure
After exposure to extremes of temperature and/or humidity for prolonged periods, the polymer sensor film can
become either very dry or very wet, in each case the result is either high or low relative humidity readings. Under
normal operating conditions, the induced error will diminish over time. From a very dry condition, such as after
shipment and soldering, the error will diminish over a few days at typical controlled ambient conditions, e.g., 48
hours of 45 ≤ %RH ≤ 55. However, from a very wet condition, recovery may take significantly longer. To accelerate
recovery from a wet condition, a bake and hydrate cycle can be implemented. This operation consists of the
following steps:
Baking the sensor at 125 °C for ≥ 12 hours
Hydration at 30 °C in 75 %RH for ≥ 10 hours
Following this cycle, the sensor will return to normal operation in typical ambient conditions after a few days.
2.10. Long Term Drift/Aging
Over long periods of time, the sensor readings may drift due to aging of the device. Standard accelerated life
testing of the TH02 has resulted in the specifications for long-term drift. This contribution to the overall sensor
accuracy accounts only for the long-term aging of the device in an otherwise benign operating environment and
does not include the affects of damage, contamination, or exposure to extreme environmental conditions.
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