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Idiomas disponibles
LP UVA 02
The LP UVA 02 radiometer measures the broadband UVA irradiance
on a plane surface (Watt/ m
). Measured irradiance is the result of the sum of direct
2
solar irradiance and of diffuse irradiance.
The radiometer can measure the UVA irradiance in closed room too.
Working Principle
The LP UVA 02 radiometer is based on a solid state sensor, the spectral match
with the desire curve is obtain using special filter. The relative spectral response is
reported on figure 1.
In order to protect the diffuser from the dust, the LP UVA 02 radiometer is equipped
with a 50mm glass dome.
The cosine low response is obtained with a particular shaped PTFE diffuser in figure
2 the cosine error versus angle of incident is reported
The good cosine low response of LP UVA 02 allow to use the radiometer at any sun
's zenithangle .
Installation and Mounting of the Radiometer for the Measurement of Global
Radiation:
Before installing the radiometer, refill the cartridge containing silica-gel crystals.
Silica gel absorbs humidity in the dome chamber and prevents (in particular climatic
conditions) internal condensation forming on the internal walls of the domes and
measurement alteration.
Do not touch the silica gel crystals with your hands while refilling the cartridge. Carry
out the following instructions in an environment as drier as possible:
1- Loosen the three screws that fix the white shade disk
2- Unscrew the silica gel cartridge using a coin
3- Remove the cartridge perforated cap
4- Open the sachet containing silica gel (supplied with the radiometer)
5- Replace the silica gel crystals
6- Close the cartridge with its own cap, paying attention that the sealing O-
ring be properly positioned.
7- Screw the cartridge to the radiometer body using a coin
8- Check that the cartridge is screwed tightly (if not, silica gel life will be
reduced)
9- Position the shade disk and screw it with the screws
10- The radiometer is ready for use
Figure N.3 shows the operations necessary to fill the cartridge with the silica gel
crystals.
• The LP UVA 02 radiometer 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 radiometer lays. If this is not possible, select a site where obstructions
do not exceed 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 radiometer has to be located far from any kind of obstruction, which might
reflect sunlight (or sun shadow) onto the radiometer itself.
• The LP UVA 02 radiometer is provided with a spirit level for carrying out an
accurate horizontal leveling. The adjustment is made by means of two leveling
screws that allow to adjust the radiometer inclination. Use the two 6mm-diameter
holes and a 65mm interaxial distance to mount the instrument on a plane. Remove
the shade disk to access the holes and reposition it after mounting (see fig. 4).
• The LP S1 mounting kit (figure 5), supplied on demand as an accessory, allows an
easy mounting of the radiometer on a mast. The mast maximum diameter shall not
exceed 50 mm. The operator shall take care that the mast height does not exceed
the radiometer plane to avoid measurement errors caused by any reflection or
shadow of the mast itself. To fix the radiometer to the mounting bracket, remove
the shade disk loosening the three screws, fix the radiometer, and mount the
white shade disk again.
• It is suggested to thermally isolate the radiometer from its mounting brackets, and
to check that the electrical contact with the ground be done properly
Electrical Connection and Requirements for Electronic Readout Devices:
• The LP UVA 02 radiometer does not require any power supply.
• Two LP UVA 02 models are available:
with a 5 m output cable (LP UVA 02-5)
with a 10m output cable (LP UVA 02-10).
• The LP UVA 02 is supplied with a PTFE, UV resistant, screened (braid) and 2-wire
cable. The colour 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 shield is connected to the housing. Connection diagram as per figure 6.
• The LP UVA 02 radiometer has to be connected either to a millivoltmeter or to a
data acquisition system with input resistance > 5MΩ. Typically, the radiometer
output signal does not exceed 20 mV. In order to better exploit the radiometer
features, the readout instrument should have a 1μV resolution.
Maintenance:
It is important to keep the outer glass dome 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.
Because of the high rise/fall in temperature between day and night, some
condensation might appear on the radiometer dome. To minimize the condensation
growth, the radiometer is provided with a cartridge containing dessicant material:
Silica gel. The efficiency of the Silica gel crystals decreases in the course of time
while absorbing humidity. Silica gel crystals are active when their color is yellow,
while they turn blue as soon as they loose their power. Read instructions about how
to replace them. Silica gel typical lifetime goes from 2 to 6 months depending on the
environment where the radiometer works.
Calibration and Measurements:
The radiometer S sensitivity (or calibration factor) allows to determine the irradiance
by measuring a signal in Volts at the ends of the resistance which short-circuits the
terminals of the photodiode ends. The S factor is measured in μV/(Wm
• Once the difference of potential (DDP) has been measured at the ends of the
sensor, the E
irradiance is obtained applying the following formula:
e
Where:
E
: is the Irradiance expressed in W/m
e
DDP: is the difference of potential expressed in μV and measured by the
multimeter,
S: is the calibration factor in μV/(W/m
mentioned in the calibration report)
Pyranometers are factory calibrated one by one and they are marked by their own
calibration factor.
The calibration is carried out following procedure N° DHLF-E-59. This procedure is
used in the SIT calibration center N° 124 for the calibration of UVA radiometer.
The calibration was performed by reference to Delta Ohm srl primary standard with
monochromatic light at 365 nm obtained separating the emission line of a Xe-Hg
lamp with an inferential filter. To get best performances from your LP UVA 02 it is
strongly recommended that the calibration be checked annually.
At the moment no international agreement exist for the calibration of this kind
of radiometer, so the calibration coefficient is dependent from the calibration
procedure like reported in the following article:
"Source of Error in UV Radiation Measurements ", T. C. Larason, C. L.
Cromer on "Journal of Reaserch of the National Institute of Standards and
Technology" Vol. 106, Num. 4, 2001. (The article is free on the NIST's WEB site
at the following address : http://www.nist.gov/jers).
Technical Specifications:
Typical sensitivity:
Response time:
Impedance:
Measuring range:
Viewing angle:
Spectral range:
Operating temperature:
Cosine response:
Long-term non-stability (1 year):
Non-linearity:
Temperature response:
Dimensions:
Weight:
-2
E
= DDP/S
e
,
2
) shown on the radiometer label (and
2
150 ÷ 350μV/(W/m
)
2
<0.5 sec (95%)
5 ÷ 7.5 KΩ
0-1000 W/m
2
2π sr
327 nm ÷ 384 nm (1/2)
312 nm ÷ 393 nm (1/10)
305 nm ÷ 400 nm (1/100)
-40 °C ÷ 80 °C
< 8 % (tra 0° e 80°)
<±3 %
<1 %
< 0.1%/°C
figura 4
0.90 Kg
).
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