PWD series
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Present Weather and Visibility Sensors PWD10, PWD12, PWD20, and PWD22 Features • Accurate and traceable measurement of prevailing visibility • Indicate the cause of reduced visibility • Identify precipitation type • Measure the intensity and accumulation of precipitation • Estimate snow accumulation Tens of thousands of Vaisala present weather and visibility sensors are installed around the world, working reliably and accurately in diverse applications and climates. In Vaisala PWD series, you 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). PWD12 and PWD22 identify the 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 3 independent measurements are processed through sophisticated algorithms to produce an accurate evaluation of the weather type according to the WMO and NWS code tables. Calibrated with reference to a highly accurate transmissometer, Vaisala PWD series sensors use the proven forward-scatter measurement principle to report meteorological optical range (MOR). The visibility sensor is well-protected against contamination: the optical components point downward and hoods protect the lenses against precipitation, spray, and dust. This weatherproof design of 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. PWD sensors are less than 1 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.

PWD sensor applications For meteorological and aviation applications With a visibility measurement range of 10–20 000 meters, PWD22 is a two-inone forward scatter visibility and present weather sensor. PWD22 is recommended for automatic weather stations, especially low-power ones that are used for general meteorological and aviation applications. PWD22’s ability to detect freezing precipitation makes it possible to issue warnings when the weather presents safety hazards for road and air traffic. Vaisala Present Weather Detector PWD22 Economical visibility measurement for road weather...

Operating principle Forward scatter measurement with Reporting range of MOR (visibility) 10-2000 m (32-6500 ft) Reporting uncertainty in operational ±10 % at 10-2000 m (32-6500 ft)]) conditions Measurement error (instrument ±2.5 % 1) Fulfills ICAO Annex 3: ±50 m (164 ft) up to 600 m (1968 ft) Operating principle Forward scatter measurement with Reporting range of MOR (visibility) 10-2000 m (32-6500 ft) Reporting uncertainty in operational ±10 % at 10-2000 m (32-6500 ft) ]) conditions Measurement error (instrument ±2.5 % Weather type identification 4 different types of precipitation (rain,...

Technical data Weight Mechanical specifications

Transmitter circuit board Transmitter optics module (includes PWT11 and lens) Controller/Receiver for PWD10 Controller/Receiver for PWD12 Controller/Receiver for PWD20 Controller/Receiver for PWD22 RAINCAP (single plate) (PWD12) RAINCAP (double plate) (PWD22, PWD52) Aluminum mast, 3 m (9 ft 10 in), 0 60 mm (2.36 in), white DKP203W Aluminum mast, 2 m (6 ft 7 in), 0 60 mm (2.36 in), white DKP202W Interface unit for powering BOX221/BOX222 Hood heaters for harsh winter conditions PWH111 Support arms for mast installations Various ]) Mounting clamps for mast top installations Various ]) 1) For...