Vaisala PWD10, PWD22, PWD12, PWD20 User Manual

P.O. Box 26, FIN-00421 Helsinki, FINLAND

Email: [e-mail]

PWD10, PWD12, PWD20 and PWD22
Present Weather and Visibility Sensors

Features/Benefits

All models:

• Accurate measurement of prevailing

visibility

• Compact and light-weight

• Easy to install

Additionally PWD12 and PWD22
models:

• Indicate the cause of prevailed

visibility

• Detect precipitation type

• Measure the intensity and

accumulation of precipitation

• Estimate snow accumulation

Tel: [phone]

Fax: [phone]

www.vaisala.com

Vaisala PWD-series of present weather detectors and visibility sensors provide you off-the­shelf accuracy and realiability. They are a sensor family that grows with your needs.

Thousands of Vaisala present weather
and visibility sensors are installed
around the world, working reliably and
accurately in diverse applications and
climates. In the Vaisala PWD-series of
present weather detectors and visibility
sensors, you will find the mix you
require of visibility measurement range
(MOR), characterization of reduced
visibility, precipitation type
identification, precipitation
accumulation/intensity measurement,
and report formats (WMO, NWS code
tables).

Proven measurement
principles for present
weather

The Vaisala Present Weather Detectors
PWD12 and PWD22 identify
precipitation type by accurately
estimating the water content of
precipitation with a capacitive device
(Vaisala RAINCAP® sensor element)
and combining this information with
optical forward scatter and temperature

measurements. These three
independent measurements are
processed through sophisticated
algorithms in order to produce an
accurate evaluation of the weather type
according to the WMO and NWS code
tables.

Accurate visibility
measurement

Calibrated with reference to a highly
accurate transmissometer, Vaisala
PWD-series sensors use the proven
forward-scatter measurement principle
to measure Meteorological Optical
Range (MOR). The visibility sensor is
well-protected against contamination:
the optical components point
downwards and hoods protect the
lenses against precipitation, spray and
dust. This weather-proof design of the
PWD sensors provides accurate
measurement results and reduces the
need for maintenance. The optional
hood heaters are recommended for
wintry conditions to prevent ice and
snow accumulation.

Economical visibility
measurement for road
weather applications

With a measurement range of 10...2,000
meters, the Vaisala Visibility Sensor
PWD10 offers economical and reliable
visibility measurement for road weather
applications. The PWD10 is
recommended for road weather
systems which alert drivers to e.g.
reduced visibility.

130

Vaisala Instruments Catalog 2005

Ref. B210435en rev. A

PWD-series PRESENT WEATHER, VISIBILITY

The Vaisala Present Weather Detector
PWD22.

The PWD22 is recommended for Automatic
Weather Observation Systems (AWOS).

PWD12 is ideal for road weather
applications.

PWD-series sensors can be used in
planning the road maintenance.

For sophisticated road
weather applications

The Vaisala Present Weather Detector
PWD12 provides accurate visibility and
present weather measurement in the
road environment, where low visibility is
a serious safety hazard and significantly
reduces traffic flow rates. With a
visibility measurement range of

10...2,000 meters, the Vaisala Present
Weather Detector PWD12 is ideal for
road weather applications. The PWD12
also indicates the cause of reduced
visibility to give you a full picture of
weather conditions. Its ability to detect
precipitation and identify precipitation
type gives the road authority valuable
information for the short-range planning
of road maintenance operations.

For meteorological and
aviation applications

With a visibility measurement range of

10...20,000 meters, the Vaisala Present
Weather Detector PWD22 is a two-in­one forward scatter visibility and
present weather sensor. The PWD22 is
recommended for automatic weather
stations (especially low-power AWSs)
that are used for general meteorological
and aviation applications. The PWD22's
ability to detect freezing precipitation
makes it possible to issue warnings
when the weather presents safety
hazards for road and air traffic.

The PWD22 is equipped with two
Vaisala RAINCAP® sensor elements to
improve detection sensitivity during
light precipitation events – even light
drizzle is detected. The PWD22 also
reports present weather in WMO
METAR code format so it is easily
integrated with AWOS systems.

Wherever visibility
measurement is needed

With a measurement range of 10...20,000
meters, the Vaisala Visibility Sensor
PWD20 offers long-range visibility
measurement for diverse applications
covering harbors, coastal areas, heliports,
windmill parks – indeed, any locations
or areas where visibility measurement is
necessary.

Easy installation

PWD sensors are less than one meter
long. All are compact, light-weight,
come with a cable and connector for
easy installation, and can be mounted
in many ways on any existing mast.

Expandable measurement
capabilities

The measurement capabilities of the
Vaisala PWD-series sensors can be
extended when your measurement
needs grow. All PWD-series sensors can
be economically upgraded to ensure
that your PWD sensor gives full value
for many years to come.

Vaisala Instruments Catalog 2005

Ref. B210435en rev. A

131