The Vaisala PWD series of present weather detectors and visibility sensors provide a mix of visibility measurement, characterization of reduced visibility, precipitation type identification, precipitation accumulation and intensity measurement, and report formats (WMO, NWS code tables).
PWD22 is included in the standard offering. The following variants are also available:
- Vaisala Visibility Sensors PWD10, PWD20, and PWD50
- Vaisala Present Weather Detectors PWD12, and PWD52
| Property | Value |
|---|---|
| IP rating | IP66 |
| Digital outputs | RS‑485 |
| Operating temperature |
PWD12: −40 … +55 °C (−40 … +131 °F) PWD10, PWD20, PWD22, PWD50, PWD52: −40 … +60 °C (−40 … +140 °F) |
| Precipitation types |
PWD10, PWD20, PWD50: None PWD12: 4 different types PWD22, PWD52: 7 different types |
| Visibility measurement range (MOR) |
PWD10, PWD12: 10 … 2 km (32 … 1.24 mi) PWD20, PWD22: 10 m … 20 km (32 ft … 12.43 mi) PWD50, PWD52: 10 m … 35 km (32 ft … 21.75 mi) |
| Visibility measurement accuracy |
PWD10, PWD12:
PWD20, PWD22:
PWD50, PWD52:
|
The visibility sensors and present weather detectors measure visibility (meteorological optical range, MOR) using the principle of a forward-scatter measurement.
In addition, the present weather detectors measure precipitation intensity, precipitation type, and precipitation accumulation. The detector estimates the precipitation water content with a capacitive device, Vaisala RAINCAP rain sensor, and combines this information with optical scatter and temperature measurements. Together, these 3 independent measurements provide sufficient data for an accurate evaluation of the prevailing visibility and weather type.