Operation And Measurement; Data Collection; Key Parts Of Smp Series Pyranometers - Kipp & Zonen SMP series Instruction Manual

5. Operation and measurement

.
SMP series pyranometers only require suitable sources of power and radiation (light) to operate and make measurements.
However, it is necessary to connect them to some sort of readout or data storage device in order to save the measurements, there
is no internal data memory.

5.1 Data collection

An optimal setting for the data interval is to sample every second and store one minute averages. For setting up the combination
of pyranometer and data storage please refer to the manual of the data collection device.
Take care when using the analogue output to match the output range of the pyranometer closely to the input range of the data
collection device to maximise the available resolution and minimise noise.
This can be done by determining the maximum expected analogue output of the pyranometer in your application and taking the
minimum input range of your data collection device that can just handle that signal.

5.2 Key parts of SMP series pyranometers

The detectors of the SMP's are based on passive thermal sensing element called a thermopile. Although the detector construction
di ers between models, the fundamental working principle is applicable to all SMP radiometers.
The thermopile responds to the total energy absorbed by a unique black surface coating developed by Kipp & Zonen, which is
non-spectrally selective. The thermopile warms up and the heat generated flows through a thermal resistance to a heat-sink, the
pyranometer housing. The temperature di erence across the thermal resistance of the detector is converted into a small voltage
as a linear function of the absorbed irradiance.
The rise of temperature in the thermopile is easily a ected by wind, rain and thermal radiation losses to the environment (for
example, a 'cold' sky) and the delicate black coating must be protected. Therefore the detector of the SMP's are shielded by two
domes (the entry-level SMP3 has only one dome to reduce size and cost). These domes allow equal transmittance of the direct
solar component for every position of the sun in the hemisphere above the detector.
drying cartridge (SMP11 only)
A drying cartridge in the SMP11 radiometer housing is filled with replaceable silica gel and prevents condensation on the inner
sides of the domes, which can cool down considerably on clear windless nights. The other SMP's have a sealed construction with
a non-replaceable internal drying cartridge. The internal desiccant lasts for 10 years.
inner glass dome
sun shield
fixed foot
smart interface
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outer glass dome
detector
bubble level
connector
housing
adjustable feet