Kippzonen CM 121 B/C Shadow Ring Manuel d'utilisateur télécharger pdf (Page 12)

3. PRINCIPLES & SPECIFICATIONS

Instruction manual CM 121

3. PRINCIPLES & SPECIFICATIONS

3.1 Theory

The objective of the shadow ring is to intercept the direct radiation coming to the pyranometer from

the sun during the whole day without readjustment. Therefore the shadow ring must satisfy the

following requirements. See also the schematic representation (fig. 2).

z Once installed, the axis of the shadow ring must be always parallel to the polar-axis. In

consequence the angle between shadow ring axis and horizontal should be equal to the

latitude of the observation site.

z The shadow ring must be able to shift along the shadow ring axis relative to the pyranometer

and in this way be adjusted to the sun's changes in declination during the year.

z Within the shadow ring construction the pyranometer must be positioned with its sensor on

the shadow ring axis.

figure 2 schematic representation of the CM 121B on earth.

Also it is shown that the sliding bar setting is a function of the solar declination.

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Kippzonen CM 121 B/C Shadow Ring Manuel d'utilisateur Page 12