Fine offset HP2550 Operation Manual page 65

(4) Only use this if you improperly installed the weather station sensor
array, and did not point the direction reference to true north.
(5) The default conversion factor based on the wavelength for bright
sunlight is 126.7 lux / w/m
photovoltaic experts based on the light wavelength of interest, but for
most weather station owners, is accurate for typical applications, such
as calculating evapotransporation and solar panel efficiency.
(6) Wind speed is the most sensitive to installation constraints. The rule
of thumb for properly installing a wind speed sensor is 4 x the
distance of the tallest obstruction. For example, if your house is 20'
tall and you mount the sensor on a 5' pole:
Distance = 4 x (20 – 5)' = 60' or =4 x (6.10-1.52)=18.32m.
Many installations are not perfect and installing the weather station
on a roof can be difficult. Thus, you can calibrate for this error with a
wind speed multiplier.
In addition to the installation challenges, wind cup bearings (moving
parts) wear over time.
Without a calibrated source, wind speed can be difficult to measure.
We recommend using a calibrated wind meter (not included) and a
constant speed, high speed fan.
(7) The rain collector is calibrated at the factory based on the funnel
diameter. The bucket tips every 0.01" or 0.1m of rain (referred to as
resolution). The accumulated rainfall can be compared to a sight glass
rain gauge with an aperture of at least 4" or 0.1m.
Make sure you periodically clean the rain gauge funnel.
2
. This variable can be adjusted by
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