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Chapter 2___________________________________________________________ Product Overview
VAISALA ________________________________________________________________________ 15
PWC22 Controller/Receiver
PWC22 Controller/Receiver measures the scattered part of the PWT11
light beam as the data signal. PWC22 contains an extra light
transmitter for monitoring lens contamination. The receiver is tilted
20° downwards. Therefore, in addition to a small side angle, the
receiver unit measures light scattered at an angle of 45°. PWD22
contains enhanced signal processing functions, which allows for a
wider measurement range.
Vaisala RAINCAP
The Vaisala RAINCAP
proportional to the amount of water on the RAINCAP
element, which is the sensing part of RAINCAP
consists of thin wires protected by an insulating glass coating. The
presence of water changes the capacitance of the plate. The
capacitance is measured by the integrated electronics. The integrated
heating resistors keep the elements dry from condensation.
®
RAINCAP
has an integrated temperature sensor for heating control.
Vaisala Present Weather Detector PWD22 is equipped with a double-
plate Vaisala RAINCAP
®
RAINCAP
elements. The tilted two-plate construction give better
sensitivity for detecting light drizzle.
Temperature Sensor (TS)
Temperature Sensor (TS) is a Pt100 thermistor that is used to measure
the crossarm temperature. See Figure 1 on page 14.
Power Supply
The power supply can be connected separately for the measurement
electronics and heating. Thus, the battery backup can be limited to the
measurement power supply.
Operating Principle
Vaisala Present Weather Detector PWD22 is a microprocessor
controlled sensor that combines optical forward scatter measurement
capacitive precipitation sensing, and temperature measurement. All
®
Rain Sensor
®
Rain Sensor Assembly produces a signal
®
Rain Sensor Assembly, which has two tilted
®
sensing
®
. This element
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Troubleshooting
