Kipp&Zonen CNR 4 Net Radiometers - Manual (Page 29)

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4 INSTALLATION AND MAINTENANCE
For measurement of the Net Radiation, it is most important that the instrument is located in a place that is
representative of the entire region that you wish to study.
When installed permanently, the net radiometer should be attached to its mounting platform with the rod that is
attached to its body.
When installed on a mast, the preferred orientation should be such that no shadow is cast on the Net Radiometer at
any time during the day. In the Northern Hemisphere this implies that the Net Radiometer should be mounted south
of the mast.
It is suggested that the CNR 4 is mounted at a height of at least 1.5 metres above the surface, to avoid shading
effects of the instruments on the soil and to promote spatial averaging of the measurement. If the instrument is H
metres above the surface, 99% of the input of the lower sensors comes from a circular area with a radius of 10 H.
Shadows or surface disturbances with radius < 0.1 H will affect the measurement by less than 1%.
The Net Radiometer should be installed horizontally, using the level on the body of the CNR 4.
For installation in buildings or in solar energy applications, you will often have to mount the CNR 4 parallel to the
surface that is being studied. This may be in a tilted, or a vertical position. The sensitivity of the radiometers will be
affected, but only in a minor way. This is specified as the so-called tilt effect. From the specifications in chapter
2.2.1 and 2.3.3 you can see that the tilt effect (this is change in sensitivity) remains within 1 %.
4.1 Replacing the drying cartridge
The Net Radiometer is an all-weather instrument.
Once installed it needs little maintenance. It is suggested that you clean the windows and domes as part of a
regular routine, using water or alcohol. The drying cartridge needs to be replaced every 2 years. The 3 screws for
the plastic cover and the 6 screws for the base plate need to be removed using a screwdriver with a Philips tip size
PH1. Under the base plate the drying cartridge is located. The (black) rubber ring as indicated in the picture below
must be in place to keep the compartment sealed.
Figure 4.1 Replacing the drying cartridge