On the top surface of the sensor a black paint is deposited which has a very rough structure containing many micro-cavities that
effectively ‘trap’ more than 95% of the incident radiation in a broad spectral range. Furthermore, the spectral selectivity is less
than 3%. This means that within the spectral range of the pyrgeometer, the absorption for each wavelength is equal to within
3%. The black painted sensing element forms the detector. Considering the long-term stability of the instrument, the black paint
is one of the most crucial and delicate parts of the pyrgeometer. Kipp & Zonen black paint gives the best possible stability over
a long period of time under all meteorological circumstances.
5.3 Temperature sensor
The housing temperature sensor is a crucial part of a pyrgeometer and is needed to calculate the downward long-wave radiation
component. The body temperature sensor represents the ‘absolute’ temperature of the detector surface and therefore it is
mounted close to the cold junctions of the detector. A housing temperature sensor is fitted as standard to the SGR pyrgeometers.
5.4 Housing
The radiometer housing accommodates all fundamental pygeometer parts. The anodized Aluminium parts are light weight and
give a high mechanical and thermal stability to the instrument. Due to its fine mechanical construction all pyrgeometers are
virtually sealed and comply to the international standard IP 67. Each pyrgeometer model can be leveled by using the bubble
level and two leveling feet. For ease of maintenance the bubble level is situated next to the window of the instrument and due
to the special shape of the sun shield it is visible from above. The sun shield acts to protects all the external parts from radiation
and to reduce solar heating of the housing.
5.5 Cable and connector
For ease of installation and replacement during recalibration of the radiometer, the SGR series are provided with a weather
proof signal cable connector.
Kipp & Zonen radiometers use a custom-made cable that is selected with a high UV resistance and low electrical resistance.
The shield of the cable is connected to the metal body of the connector and preferably should be connected to ground at the
readout equipment. Cables come pre-wired to the connector plug in a range of lengths.
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