OTT HydroMet KIPP&ZONEN SMP12 Notice D'utilisation page 11

Product description | 3
3 Product description
3.1 Design and function
The SMP12 Smart Pyranometer measures the irradiance of the sun on a planar surface that results from the
combination of direct solar radiation and diffuse sky radiation. Two pyranometers can be used as
albedometers in order to measure the sky radiation and the surface reflection at the same time.
In order to take measurements, the pyranometer requires an appropriate voltage supply and an appropriate
radiation source (light). The pyranometer needs to be connected to an evaluation unit or a data logger to save
the measurements. The pyranometer does not have any internal data memory. It communicates with a
programmable logic controller (PLC) via the RS-485 interface using the Modbus protocol.
The pyranometer's sensor element consists of a passive thermopile. The thermopile responds to the total
energy that is absorbed by the spectrally non-selective diffuser and heats up. A thermal resistor transfers the
resulting heat to the heat sink (pyranometer housing). The temperature difference on the sensor element's
thermal resistor is converted into an output voltage that is linear to the absorbed solar radiation.
To allow a steady measurement that is independent of the ambient conditions, the thermopile is shielded by a
glass dome. The glass dome allows direct radiation to be uniformly distributed even as the sun's position
changes relative to the sensor. In the process, the sun shade reduces the extent by which solar radiation heats
up the housing. Any moisture that penetrates the product is absorbed by the desiccant inside the housing.
To facilitate installation and recalibration, there is a waterproof connection socket on the housing, for which a
matching connector is also delivered. The connector may be delivered loose or with a cable. The pyranometer
can be oriented using the spirit level on the housing and the adjustable feet.
SMP12 Smart Pyranometer | EN 11