Using Pwd22 - Vaisala PWD22 User Manual

Chapter 2___________________________________________________________ Product Overview
VAISALA ________________________________________________________________________ 17
The output of RAINCAP
capacitive sensing surfaces while the optical intensity is proportional
to the volume of the reflecting particles. The ratio of optical and
capacitive intensities is used to determine the basic precipitation type.
The crossarm temperature (TS) is measured using the Pt100
temperature sensor. The temperature data together with the optical
signal profile and the RAINCAP
determine the actual weather code.
Several parameters are available for the operator for configuring and
adjusting the PWD22 operation.

Using PWD22

PWD22 is typically used as a component of a weather observing
system.
The PWD22 output is either a digital serial interface or an analog
current signal. The digital serial interface can be configured into two
different operating modes: the sensor can be set to send a data
message automatically at selected intervals, or PWD22 can be polled
by the host computer. The same serial line is also used as an operator
interface. The analog current signal can be used to report the
prevailing visibility. Three relay controls can be used, driven by
visibility limits.
The operator controls and checks the operation of PWD22 using a
maintenance terminal. A set of built-in commands and test routines
are provided for configuring and monitoring the multiple functions of
PWD22.
The standard data messages contain a status character for indicating
faults detected by the internal diagnostics. If the error status is set, the
operator can display a special status message, which contains the
detailed results of the diagnostics and a written description of the
fault. With this information the operator can take corrective action or
give the maintenance personnel advice.
®
is proportional to the water amount on the
®
surface sensor data are used to