Features

• Suitable for all latitudes and all tilted surfaces
• Correction factors are given in the manual
• The shadow from the ring covers the pyranometer dome completely
• The ring will not need adjustment for several days
• The U-profile intercepts the circumsolar part of the sky more constantly then an I-profile.

The combination of a CM 121 shadow ring and a pyranometers, smart pyranometers, pyrgeometers or UV radiometers offers a simple solution for the measurement of the diffuse solar radiation. The specific advantages of this type of shadowing are that it is suitable for installation anywhere on earth (contrary to designs that require the specification of a particular latitude), that it can be combined with a ventilation unit, and that it has a special U-profile ring which simplifies the mathematical correction for intercepted diffuse radiation.

The shadow ring will keep the pyranometer in the shade during the entire day, preventing the direct solar radiation to reach the sensor. As a result only the diffuse solar radiation is measured. A regular schedule of maintenance would require manual adjustment of the sliding bars (that are connected to the actual shadow ring) every two or three days. This adjustment is necessary because the elevation of the solar course changes slightly from day to day. For proper setting of the sliding bars, the table of “correction factors and the sliding bar setting” can be consulted.

Normally, the sensor will be in the horizontal position but the CM 121 allows for it to be mounted in tilted positions along the north-south axis. The ring itself is equipped with a special U-profile so that it has a nearly constant view angle during the year. A stable stand is also guaranteed even at high winds. The shadow ring will intercept a proportion of the diffuse sky radiation and any measurements should be compensated by using the correction factors provided with the unit.

Specifications