Environmental Engineering Reference
In-Depth Information
12a
10
4
10
0
terrestrial solar radiation
10
3
10
2
10
-1
10
1
10
-2
10
0
E
Ery
= 0.118 W/m²
10
-1
10
-3
10
-2
E
RB-M
= 0.119 W/m²
10
-3
10
-4
260
280
300
320
340
360
380
400
Wavelength (nm)
12b
10
4
10
0
10
3
sun ray lamp
10
-1
10
2
10
1
10
-2
10
0
E
Ery
= 2.5 W/m²
10
-1
10
-3
10
-2
E
RB-M
= 0.67 W/m²
10
-4
10
-3
260
280
300
320
340
360
380
400
Wavelength (nm)
Figure 12.
Comparison of the erythema action spectrum according to CIE
16
and the efficiency of a
Robertson-Berger meter [manual UV Biometer 501] as an example of a broadband radiometer.
In the case of terrestrial solar radiation (Fig. 12a) the detector reading agrees very well with the true
erythema effective irradiance. But for sources with emission in the wavelength range, where the
detector efficiency and the action spectrum differ from each other, large deviations between the
reading and the true value occur.
The measurement of solar UV radiation is a very exacting task. Due to the
steepness of the spectral cut-off at about 300 nm high sensitivity and spectral resolution
are required. On the other hand rapidly changing cloud conditions require fast
responding instruments. Furthermore, field experiments call for light weight, battery
operated devices which are easy to handle. There is until now no “general purpose”
instrument which covers all types of applications. Spectroradiometers are necessary to
assess the exact position of the UV cut-off and for the determination of biological action
spectra. Broadband instruments can be applied much easier in field experiments and in
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