Kipp&Zonen CHP 1 Pyrheliometer - Manual (Page 12)

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5.6 Field of view
Figure 4 shows the pyrheliometers optical construction.
Figure 4: Optical construction
The beam of light that reaches the detector is limited by the field and aperture stop. The slope, opening and limit
angles are determined by R, r and L. The distance x is negligible.
For the CHP 1 the full opening angle is 5
°, the slope angle is 1 °. The sun, as seen from the detector, occupies a
solid angle of 0.5 °. A 100 % response can be expected only if the sun is entirely within the slope angle. This is the
case when tracking accuracy is better than slope angle minus half the solar angle.
Concluding, tracking accuracy should be within 0.75
° of ideal.
5.7 Environmental
The CHP 1 pyrheliometer is designed for outdoor use under all expected weather conditions. The radiometers
comply with IP 67 and their solid mechanical construction is suitable to be used under all environmental conditions
within the specified ranges.