Campbell Scientific CS125 Present Weather Sensor - Manual (Page 22)

CS125 Present Weather Sensor
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9. CS215 T/RH Sensor
A CS215 temperature and RH sensor can be connected to the CS125. This is
recommended as it will improve the performance of the CS125 in identifying
precipitation and allows it to, for example, distinguish between mist and haze.
Precipitation identification at temperatures close to freezing will be much
improved by a CS215 and its use is highly recommended in regions where
temperatures close to 0°C are common if information on precipitation type is
important. It also allows RH information to be included in data messages.
If a CS215 is connected then the temperature used for assessment of precipitation
type and included in data messages will come from the CS215 instead of the
temperature sensor mounted in the cross arm.
The connections for the CS215 are shown below. The CS215 itself can be
mounted in a Met20 screen on the same mast as the CS125. The screen can be
mounted on the top section of an OSM1 optical mast below a CS125.
WMO – No. 8, 2.1.4.1 recommends temperature measurement at a height of
between 1.2 and 2.0 m above ground. The screen should be below the height of
the CS125 electronics box.