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3. Mounting
The CGR pyrgeometer is provided with two holes for 5 mm bolts. Two each of stainless steel bolts,
washers, nuts and nylon insulation rings are provided in the fixing kit. The pyrgeometer should first be
secured lightly with the bolts to a solid and stable mounting stand or platform as shown in Figure 1. After
recalibration the nylon insulators must be replaced with new ones to prevent corrosion.
The mounting stand temperature can vary over a wider range than the air temperature. Temperature
fluctuations of the pyrgeometer body can produce o set signals, therefore it is recommended to isolate
the pyrgeometer thermally from the mounting stand by placing it on its levelling screws. Ensure that
there is a good electrical contact with earth to conduct away currents in the cable shield induced by
lightning.
Note: After recalibration and/or reinstallation the nylon insulators must be replaced with new ones to maintain durability.
4. Orientation
In principle no special orientation of the instrument is required, although the World Meteorological
Organisation (WMO) recommends that the signal lead is pointed towards the nearest pole, to minimise
heating of the electrical connections.
5. Level pyrgeometer
Accurate measurement of the global radiation requires proper levelling of the thermopile surface. Level
the instrument by turning the two levelling screws to bring the bubble of the spirit level centrally within
the marked ring. For easy levelling, first use the screw nearest to the spirit level. When the pyrgeometer
is placed horizontally using the bubble level, or when it is mounted with its base directly on a horizontal
plane, the thermopile is horizontal within 0.1°.
Figure 1: Pyrgeometer installation
CGR 4 Manual
Page 7
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