Campbell CM 21, Инструкция по эксплуатации, Страница: 25 / 65

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3.2.4 Installation for measurement of diffuse radiation
For measuring sky radiation, the direct
solar radiation is best intercepted by a
small disk or sphere. The shadow of
the disk must cover the pyranometer
domes completely. However, to follow
the sun's apparent motion, a power-
driven tracking device is necessary.
This can be done with the 2AP tracker,
designed to track the sun under all
weather conditions. More information
about the combination of CM 21 and
tracker is given in the 2AP tracker
manual.
Figure 9 2AP tracker with pyranometer
Alternatively the use of a shadow ring is possible, however less accurate.
The shadow ring intercepts the direct solar radiation some days without
readjustment, but also a proportion of the diffuse sky radiation. Therefore
corrections for this to the recorded data are necessary.
Kipp & Zonen supplies a universal shadow ring CM 121 for all latitudes. In
the CM 121 manual, installation instructions and correction factors are given.
3.2.5 Installation for measurement of albedo
The lower sensor of the albedometer construction, the pyranometer in the
inverted position, measures the reflected solar radiation.
According to the WMO the height should be 1-2 meters above a surface
covered by short cut grass.
The mounting device should not interfere too much with the field of view of
the instrument. A construction as in figure 10 is suitable.
The upper screen prevents excessive heating of the pyranometer body by
solar radiation.
3. INSTALLATION