Temperature Sensor; Applications; Figure 5 Pwl111 Block Diagram - Vaisala PWD22/52 User Manual

Chapter 3 ______________________________________________________ Functional Description

Applications

VAISALA _______________________________________________________________________ 25
Figure 5 PWL111 Block Diagram

Temperature Sensor

The primary temperature sensor of PWD22/52 is a Pt100 thermistor
attached to the cross arm. The temperature is measured once a minute
using a high resolution A/D converter.
The sensor cross arm 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.
Obviously the (automatic) weather station that uses the PWD22/52 data
can in many cases also use other weather parameters to select from the
three PWD22/52 codes or even correct them. For example, humidity
measurement can be used to select between smoke, fog, mist, and haze.
The 15-minute code might be a good selection for a general-purpose
report.
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