LP PYRA Installation and Mounting of the Pyranometer for the Measurement of Global Radiation:

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1 CENTRO DI TARATURA SIT N 124 TEL r.a. FAX Introduction LP PYRA 03 The LP PYRA 03 pyranometer measures the irradiance on a plane surface (Watt/ m 2 ). Measured irradiance is the result of the sum of direct solar irradiance and of diffuse irradiance. The LP PYRA 03 is a Second Class pyranometer in accordance with ISO 9060 standard and with the criteria of the WMO Guide to Meteorological Instruments and Methods of Observation, fifth edition (1983). 2 Working Principle The LP PYRA 03 pyranometer is based on a thermopile sensor. The thermopile sensitive surface is coated with a black matt paint, which allows the pyranometer not to be selective at different wave lengths. The pyranometer spectral range is determined by the transmission of the two glass domes type K5. Radiant energy is absorbed by the thermopile black surface, creating a difference of temperature between the center of the thermopile (hot junction) and the pyranometer body (cold junction). Thanks to the Seebeck effect, the difference of temperature between hot and cold junction is converted into a Difference of Potential. In order to grant the thermopile a proper thermal insulation from the wind and to reduce the sensitivity to thermal irradiance, the LP PYRA 03 is equipped with a 4mm thick dome having an outer diameter of 32mm. The dome protects the thermopile from the dust, which, laying down on the black surface, might change spectral sensitivity. To prevent internal condensation forming on the internal side of the dome, three silica gel tablets are inserted inside the pyranometer to absorb humidity. 3 Installation and Mounting of the Pyranometer for the Measurement of Global Radiation: The PYRA 03 pyranometer has to be mounted in a readily accessible location to clean the dome regularly and to carry out maintenance. At the same time, check that no building, construction, tree or obstruction exceeds the horizontal plane where the pyranometer lays. If this is not possible, select a site where obstructions do not exceed - 1 -

2 5 degrees of elevation, in the path followed by the sun, between earliest sunrise and latest sunset. N.B The presence of obstructions on the horizon line significantly affects the measurement of direct irradiance. The pyranometer has to be located far from any kind of obstruction, which might reflect sunlight (or sun shadow) onto the pyranometer itself. Pursuant to ISO TR9901 standard and to WMO recommendations, when a pyranometer is used without the white shade disk, it has to be positioned in such a way that the power line is pointed to the North Pole, if the instrument is used in the Northern Hemisphere, and to the Southern pole, if used in the Southern Hemisphere. In any case, it is better to fulfill this suggestion even when the shade disk is applied. For an accurate horizontal positioning (leveling), the LP PYRA 03 pyranometer can be combined with the LPS2 support, provided with a spirit level (figure 2). The two holes having a 6mm diameter and a 47mm interaxial distance, allow and easy and stable mounting of the support to the pyranometer body. 54,0 mm Fixing/mounting hole ø6mm 47,0 mm 32.0 mm 24.0 mm 16,0 mm 50,0 mm Fig 1-2 -

3 100 mm LP SP mm 20.0 mm 300 mm 87.0 mm Fig. 2 LP S mm 4 Electrical Connection and Requirements for Electronic Readout Devices: The LP PYRA 03 pyranometer does not require any power supply. Two LP PYRA 03 versions are available: with a 5 m output cable (LP PYRA 03-5) with a 10m output cable (LP PYRA 03-10). The LP PYRA 03 is supplied with a PTFE, UV resistant, screened (braid) and 2-core cable. The color code is: Black connected to the housing (screen) Red (+) positive pole of the signal generated by the detector Blue (-) negative pole of the signal generated by the detector The LP PYRA 03 pyranometer has to be connected either to a millivoltmeter or to a data acquisition system. Typically, the pyranometer output signal does not exceed 20 mv. In order to better exploit the pyranometer features, the readout instrument should have a 1µV resolution. Case Thermopile - + Screen (black) Blue Fig. 3 Red - 3 -

4 5 Maintenance: It is important to keep the outer glass domes clean to grant measurement best accuracy. Consequently, the more the dome will be kept clean, the more measurements will be accurate. Washing can be made using water and standard papers for lens, or, in some cases, using pure ETHYL alcohol. After using alcohol, clean again the dome with water only. 6 Calibration and Measurements: The pyranometer S sensitivity (or calibration factor) allows to determine irradiance by measuring a signal in Volts at the thermopile ends. The S factor is measured in µv/(wm -2 ). Once the difference of potential (DDP) has been measured at the ends of the sensor, the E e irradiance is obtained applying the following formula: E e = DDP/S where; E e : is the irradiance expressed in W/m 2, DDP: is the difference of potential expressed in µv measured by the multimeter, S: is the calibration factor in µv/(w/m 2) shown on the pyranometer label (and mentioned on the calibration report). Pyranometers are factory calibrated one by one and they are marked by their own calibration factor. To get best performances from your LP PYRA 02/03 it is strongly recommended that the calibration be checked annually. The instruments and the equipment of Delta Ohm Photo-Radiometry meteorological laboratory grant the calibration of pyranometers according to the WMO specifications and assure that measurements are traceable to the international standards. 7 Technical Specifications: Typical sensitivity: 10 µv/(w/m 2 ) Impedance: 33 Ω 45 Ω Measuring Range: W/m 2 Viewing angle: 2π sr Spectral range: 305 nm 2800 nm W/m 2 (50%) (Dome transmission Figure 4) 335 nm 2200 nm W/m 2 (95%) Operating Temperature: -40 C 80 C - 4 -

5 Dimensions: figure 1 Weight: 0.45 Kg Technical Specifications According to ISO Response Time: <30 sec (95%) 2- Zero off-set: a) response to a 200W/m 2 thermal radiation: < 25 W/m 2 b) response to a 5K/h change in ambient temperature: < 6 W/m 2 3a- Long-term non-stability: < ±2.5 % (1 year) 3b- Non-linearity: < ±2 % 3c- Cosine Response < ±22 W/m 2 3d- Spectral selectivity: < ±7 % 3e- Temperature response <8 % 3f- Tilt response: < ±4 % - 5 -

6 8 Ordering Codes ORDERING CODE LP PYRA 03-5 LP PYRA LP S2 LP SP2 ARTICLE Second Class Pyranometer according to ISO Complete with calibration report. 5m long output cable. Second Class Pyranometer according to ISO Complete with calibration report. 10m long output cable. Mounting kit including a support with a spirit level to fix LP PYRA 03 pyranometers. Fastener screws of the pyranometer to the support and LP SP2 shade disk also included in the mounting kit. Shade disk