33784 V1.0
Yoyolog User Guide
www.grantinstruments.com
Page 35
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Important notes for measuring humidity
The Yoyo humidity/temperature probes are a precise, reliable humidity sensor element
which has a good long-term stability. The capacitive sensor allows for humidity measure-
ment in many applications and will give stable readings in clean environments for several
years.
Depending on the environmental conditions the sensor can become contaminated by for
example: dust, chemicals and dirty water which will reduce the active life.
There are further limitations, the sensor may be used in an operating range of 0-100%
RH this operating range is reduced at as the operating temperature increases. See the
graph below. This is due to the fact that quite an aggressive environment is developed
when measuring high humidity and high temperature at the same time:
The sensor should not be damaged when condensation occurs occasionally. If conden-
sation does occur, dry out the sensor in order to return to the correct measurements,
except the sensor polymer is contaminated with substances (see above).
If condensation occurs regularly or for a long period of time, the sensor life is reduced.
If the sensor is even saturated it may give incorrect readings in the range of 0-100% RH
(sometimes even negative readings), but will recover when water droplets have evapo-
rated. To ensure high quality readings we therefore recommend that probes/loggers are
verified and calibrated on an annual basis.
Operating conditions
-- -- Normal/Range
-- -- Max. Range
Humidity
Temperature
