Kipp&Zonen CM 121 B/C Shadow Ring - Manual (Page 19)

4. MOUNTING AND ALIGNMENT
Instruction manual CM 121 18
4.4 Setting of the shadow ring sliding bars (regular servicing procedure)
The correct shadow ring position is a function of the declination of the sun and it varies across the
year.
The only thing that needs to be done to readjust the position of the ring is to set the sliding bars. A
readjustment is necessary only after a few days. A regular schedule would require redjustment
every two days. However, in most seasons a longer time interval between adjustments is possible.
This can be seen in the table in 5.2.
z
Unscrew the fixing screws of the sliding bars.
z Set the sliding bars using the sun or the table of 5.2. On clear days the setting of
the ring can be done by observing the shadow of the ring on the pyranometer. If
correctly aligned the outer dome of the pyranometer must be completely shaded.
(The dome shadow on the white screen is covered by the ring shadow.) On
cloudy days the ring can be set according to the date with the aid of the scale on
the sliding bars and the table of settings. See table 1 of 5.2 lowest row. The
relevant figure must be read off at upper side of the crossbar, see figure 1.
Please mind that the scale has two sections, centered around zero. At positive
declinations of the sun (21 March-23 Sept.) the part of the scale that is used must
be in the southern or lower part of the scale. At negative declinations of the sun
(23 Sept.-21 March) the part of the scale that is used must be in the northern or
higher part of the scale. See figure 2. The figures for the sliding bar adjustment
in this row are derived with the formula L = 297 tan (D), in which D is the
declination of the sun. The values of declination and sliding bar setting
correspond with the date intervals in the same table.
z Relock the fixing screws