User's Guide _______________________________________________________________________
24____________________________________________________________________ M210543EN-B
0310-001
Figure 5
PWL111 Block Diagram
Temperature Sensor
The primary temperature sensor of PWD22 is a Pt100 thermistor
attached to the crossarm. The temperature is measured once a minute
using a high resolution A/D converter.
The sensor crossarm temperature (TS) is used to select the default
precipitation type. The sensor is not shielded from solar radiation, so it
does not measure the exact air temperature. In rain, however, the
radiation error is acceptable because of the shading of the clouds.
RAINCAP
®
Signal Processing
The RAINCAP
®
output frequency is measured once a second by the
CPU. The frequency drops when the sensing elements become wet
(see Figure 6 on page 25).
