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Figure 3
1. Relative spectral transmittance of two pyranometer domes. (Four
surface reflections and index change with wavelength are taken
into account).
2. Spectral distribution of solar radiation at sea level. Sun at zenith
(Airmass 1).
1.2.3 Directional error
The directional response is an individual feature and depends on
imperfections of the glass domes and angular reflection properties of
the black paint.
1.2.4 Temperature dependence
For a given heat flow the sensitivity of the pyranometer is a function of
the thermal conductivity of the substrate and of the thermo-electric
power of the thermocouple material. These physical quantities show
temperature dependency, and a thermistor is applied in the electric
circuit to keep the sensitivity constant at least for temperatures
between -10 °C and + 40 °C. See figure 9.
GENERAL INFORMATION
11
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