Kippzonen CM 4 Pyranometer Manual do Utilizador descarregar pdf (Página 16)

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min. cosine error

typical cosine error

max. cosine error

degrees

[%]

Figure 1.4: The mean cosine response of the pyranometer. With the angle

of incidence on the horizontal axis and the percentage deviation

from ideal cosine behaviour on the vertical axis.

1.2.4 Non-linearity

Non-linearity is the error of the sensitivity variation as a function of

the variation in irradiance. ISO 9060 defines non-linearity of an

instrument as its percentage deviation from the responsitivity at 500

W/m² due to the change in irradiance within 100 W/m² to 1000 W/m².

The linearity however is strongly related to the pyranometer design

and body. Due to a thermal gradient over the hot and cold junctions

(by absorption of radiation) heat convection at the detector surface

causes a non-linearity effect. The CM 4 detector construction has

been designed to keep the thermal gradient very low. Even when the

pyranometer is exposed to a very intense artificial radiating source

the non-linearity of the sensor sensitivity is small. The CM 4 non-

linearity is show in figure 1.5.

1. GENERAL INFORMATION

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