LPPYRA13
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V2.3
3.2
P
OSITIONING THE INSTRUMENT FOR THE DIFFUSE RADIATION MEASUREMENT
The shadow ring particular geometry allows intercepting the solar direct radiation dur-
ing the whole day without adjustments.
The base of the instrument has to be mounted parallel to the ground by adjusting the
screw with ring nut and with the aid of the levelling device integrated in the instrument.
The shadow ring has to be positioned in such a way that its axis be parallel to the
earth axis. To do this, follow two separate steps: first align the shadow ring along the
North-South axis and then adjust the ring tilt.
Fig. 3.3: positioning the instrument
Aligning the shadow ring along the North-South axis:
1.
Wait for solar midday.
2.
On the goniometer where the pyranometer is mounted there is a groove, rotate the
shadow ring base until the sunbeams pass through the groove from both sides of
the goniometer.
Fig. 3.4: shadow ring North-South alignment
As you get closer to the equator, this method involves
an increasing uncertainty. For
installations in sites nearby the equator, it is suggested to use a map to align the
shadow ring along the North-South axis.
Shadow ring axis
Earth axis
North Pole
South Pole
Equator
Solar radiation
Sunrays
Summary of Contents for Delta OHM LPPYRA13
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