Kipp&Zonen CM 121 B/C Shadow Ring - Manual (Page 13)

3. PRINCIPLES & SPECIFICATIONS
Instruction manual CM 121 12
3.2 Construction
The crossbar is one of the main parts of CM 121B. By rotating the crossbar the angle between
shadow ring axis and horizontal earth surface can be set for the particular location. This is an
operation that needs to be performed only once for installation at a certain location. The pyranome-
ter support is fixed to the crossbar, so the sensor stays in the center of the ring no matter the tilt
angle of the ring. For getting the pyranometer in the horizontal position, the so-called sector can be
rotated. See fig. 1.
With the sliding bars the shadow ring can shift along its axis. For this the fixing screws need tempo-
rarily to be unscrewed.
The normal situation is that the pyranometer is placed in the horizontal position. However, the
sector allows the pyranometer to rotate while keeping the sensor on the same position relative to
the ring, so that it is possible to mount the pyranometer in a tilted position along the north south
axis.
Measurement of the diffuse radiation on a plane tilted to the south or north is now possible, a
feature especially attractive in the application of solar collector testing.
For a site on latitude B the tilt range is B degrees to the equator and 90-B degrees to the nearest
pole.
3.3 Specifications
Material
Anodized Aluminum of seawater proof quality,
Stainless steel
Weight incl. pyranometer CM 11 5.8 kg
Mounting base See figure 5
Ring outer diameter 620 mm.
Ring width 55 mm.
Ring width/ring radius ratio 0.185
View angle (The apparent width of the
ring as seen from the pyranometer)
10.6 0
U-profile shadow ring defines the accuracy of the view angle
constant within ± 2%