
4
Humidity
/ TECHNOLOGY DESCRIPTION
Vaisala HUMICAP® Sensor for Measuring
Relative Humidity
In 1973, Vaisala introduced HUMICAP
®
, the world’s first thin-
film capacitive humidity sensor. Since then, Vaisala has
become the market leader in relative humidity measurements,
and thin-film capacitive humidity sensors have developed from
one company’s innovation into a global industry standard.
Box headline here
HUMICAP in Brief
▪
A capacitive thin-film polymer
sensor
▪
Full measurement range
0...100 %RH
▪
Accurate to ±1 %RH
▪
Traceable humidity
measurement
▪
Nearly 40 years on the market
HUMICAP’s Unique Benefits
▪
Excellent long-term stability
▪
Insensitive to dust and most
chemicals
▪
Chemical purge option
for stable measurements
in environments with high
concentrations of chemicals
▪
Sensor heating for
measurements even in
condensing environments
▪
Full recovery from
condensation
Vaisala HUMICAP sensors guarantee
quality and reliability, with their
reputation for accuracy, excellent
long-term stability, and negligible
hysteresis.
How It Works
HUMICAP is a capacitive thin-film
polymer sensor consisting of a
substrate on which a thin film of
polymer is deposited between two
conductive electrodes. The sensing
surface is coated with a porous
metal electrode to protect it from
contamination and exposure to
condensation. The substrate is
typically glass or ceramic.
The thin-film polymer either absorbs
or releases water vapor as the
relative humidity of the ambient
air rises or falls. The dielectric
properties of the polymer film
depend on the amount of absorbed
water. As the relative humidity
around the sensor changes,
the dielectric properties of the
polymer film change, and so does
the capacitance of the sensor. The
instrument’s electronics measure
the capacitance of the sensor and
convert it into a humidity reading.
Typical Applications for
Humidity Measurement
Vaisala’s humidity instruments with
HUMICAP sensors are suitable for
a wide range of applications. From
power and steel to life sciences and
building automation, many industries
need to measure humidity – here are
just a few:
Humidity must be measured and
controlled in many drying processes,
such as those in construction
material and paper manufacturing,
and fluid bed dryers. The humidity
of the process air is a good indicator
of the progression of the drying
process.
Cleanrooms and other critical
environments also require high-
performance environmental
measurements in order to operate
consistently and within
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