Shadow Ring Site Selection
It is recommended to install the Shadow-Ring in a readily accessible location to perform routine cleaning of the pyranometer dome and to perform mechanical readjustment, at least every two days. The installation site should be free from local obstructions (e.g. buildings, trees, towers) that exceed the horizontal plane of the pyranometer. If this is not possible, select an installation site in which local obstructions do not exceed 5 degrees elevation within the path of the daily solar course at sunrise and sunset conditions. This is critical when using a second NON shaded global pyranometer to calculate the direct solar disk component in conjunction with the mounted shaded/diffuse pyranometer measurement. Care must be taken to avoid local structures that may cast shadow effects or generate increased solar reflectivity effects at certain times of day.
It is critical to mount on a stable mounting surface to ensure that the shadow-ring and pyranometer remain as perfectly level as possible throughout the field measurement campaign.
Shadow Ring Positioning & Adjustment
The shading geometry of the Shadow Ring, when properly installed and adjusted, obstructs the daily direct solar beam from irradiating the pyranometer mounted on it, from sunrise to sunset. The pyranometer should be mounted on the Shadow Ring goniometer so that the pyranometer cable gland and signal cable are oriented pointing North upon installation (i.e. assuming installation in the northern hemisphere). For installation in the southern hemisphere, the pyranometer should be mounted with the pyranometer cable gland and signal cable oriented pointing south.
The mounting base of the Shadow Ring must be installed parallel and level to the ground below. The leveling base adjustment screws and the spirit level allow for easy and accurate leveling.
Sliding Bar Tilt Adjustment
1. Confirm that the shadow-ring sliding bars and the long side of the pyranometer support are parallel (instruments are delivered factory aligned).
2. Mount the pyranometer on the goniometer head with supplied metric stainless screws.
3. Adjust the goniometer so that the scale indicator matches that of the local latitude of installation, then retighten the goniometer locking screw.
4. Rotate the crossbar (after loosening the crossbar locking screw) until the pyranometer is parallel/level with respect to the ground below;
Notes: If the above steps have been carried out correctly, the shadow-ring axis will be parallel to the Earth’s axis.
5. Finally adjust the height of the sliding bars until the pyranometer inner dome is centred within the shadow cast by the shadow-ring.