User`s guide

Chapter 2 __________________________________________________________ Product Overview
VAISALA _______________________________________________________________________ 25
weather sensor. In addition, PWD11A can measure the intensity and
amount of both liquid and solid precipitation.
The versatility of PWD11A is achieved with a unique operating
principle. PWD11A measures an estimate of the precipitation water
content with a capacitive device and combines this information with
optical scatter and temperature measurements. These three
independent measurements together sufficiently provide data for an
accurate evaluation of the prevailing visibility and weather type.
PWD11A is calibrated with reference to a highly accurate
transmissometer. An extensive self-diagnostic procedure continuously
monitors the sensor status. Dirt and foreign particles on the lens are
detected automatically, minimizing the risk of false high values. A
special calibration kit is provided as an option for conducting field
calibration under practically all weather conditions.
PWD11A is small and lightweight, thus being easy to install on the
sensor cross arm. In addition to the standard sensor operation, the
MAWS software adds extra features such as reporting of coded
weather type identifications as plain text in the output reports.
Lightning Detector SA20M
0306-022
Figure 14 Lightning Detector SA20M
Lightning Detector SA20M detects the position of lightning activity
and reports lightning and thunderstorm positions with respect to the
location of SA20M. A stand-alone thunderstorm sensor is self-
contained and weather-tight.
The SA20M sensor detects cloud-to-cloud, cloud-to-air and cloud-to-
ground lightning activity to a range of 90 km (50 nmi.). The ability to
detect inter-cloud activity allows SA20M to report lightning during