SOLAR RADIATION AND ITS MEASUREMENT - Environmental UV Radiation: Impact on Ecosystems and Human Health and Predictive Models - page 30

finally fed into a low-noise dc or chopper amplifier chain and is digitally processed for
further use. Photomultipliers require a very constant high voltage. They have a long
warm up time up to 48h; therefore, the high voltage should be buffered with a
uninterruptible power supply.
System Configuration . The complete set-up of a double monochromator scanning
spectroradiometer is depicted in Fig. 8. Particularly double monochromators systems
are subject to changes in responsivity due to mechanical strain and temperature
changes. They should be mounted on a rigid base. For outdoor use a thermally stabilised
cabinet is mandatory.

Calibration Unit

Cos-Diffusor

Quartz Fiber

D ouble-
Monochromator

Grating control

Photomultiplier

Analog signal
processing

Controller / Data aquisition

Ther m a l ly s t ab i l i sed cab i net

Read Out / Display / Data bank

Figure 8. Schematic configuration of a spectroradiometer system.