LP NET 07_1

LP NET 07 – Net Irradiance Meter

LP NET 07 measures the net radiation across a surface, from near ultraviolet to
far infrared. The Net radiation is defined as the difference between the radiation
that reaches the upper surface and the irradiation on the lower surface of the net
radiometer. The surface of the upper receiver measures the direct solar radiation
plus the diffuse one and the radiation at longer wavelengths emitted from
the sky (clouds), while the lower receiving area measures the solar radiation
reflected from the ground (albedo) and the radiation length wavelengths emitted
from the earth.
The instrument is designed and constructed to be used outdoors in any weather
conditions.
Besides its use in meteorology to measure energy balance, the LP NET 07 can
be used indoors for the measurement of radiant temperature (ISO 7726)

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Product Description

LP NET 07 measures the net radiation across a surface, from near ultraviolet to
far infrared. The Net radiation is defined as the difference between the radiation
that reaches the upper surface and the irradiation on the lower surface of the net
radiometer. The surface of the upper receiver measures the direct solar radiation
plus the diffuse one and the radiation at longer wavelengths emitted from
the sky (clouds), while the lower receiving area measures the solar radiation
reflected from the ground (albedo) and the radiation length wavelengths emitted
from the earth.
The instrument is designed and constructed to be used outdoors in any weather
conditions.
Besides its use in meteorology to measure energy balance, the LP NET 07 can
be used indoors for the measurement of radiant temperature (ISO 7726)

Working Principle
The net radiometer LP NET 07 is based on a thermopile sensor whose warm
joints are in thermal contact with the receiver while the upper cool joints are in
thermal contact with the lower receiver. The temperature difference between the
two receivers is proportional to the net irradiation. The temperature difference
between hot and cold junction is converted into a voltage by Seebeck effect. The
two receivers are made from a portion of spherical coated Teflon®. The particular
form of the two receivers provides a response in accordance with the cosine.
The Teflon® coating, as well as allowing outdoor installation for long periods
without risk of damage, can have a constant spectral response from ultraviolet
(200nm) up to far infrared (100 μm).
Installing and mounting the net radiometer for total irradiance measurements:
• To allow cleaning the two receiving surfaces regularly, LP NET 07 should be
mounted in easily reachable places. The surfaces can be washed with plain
water or pure ETHIL alcohol.
• Mount the instrument so that no shadow will be cast on it at any time of day
and of the seasons, from obstructions such as buildings, trees, or any other
obstacle.
• In the NORTHERN hemisphere, the net radiometer is normally oriented
towards SOUTH, while it should be oriented NORTHWARD, in the SOUTHERN
hemisphere.
• The instrument should be mounted at a height of at least 1.5 m above the
ground. Please note that the flow on the lower receiver is representative of a
circular area with a radius of 10 times the height.
• When installing the net-radiometer avoid, wherever possible, to touch the
surfaces of the receiving net-radiometer.

Electrical Connections and requirements for electronic reading:
• LP NET 07 does not require any power supply.
• It is available with a 5 m output cable
• It is supplied with a PTFE, UV resistant, braided shield and 2-wire cable. The
colour code is as follows:
black → connected to the housing
red → (+) positive pole of the signal generated by the detector
blue → (-) negative pole of the signal generated by the detector
Fig.1 shows the wiring diagram.
• It has to be connected to a millivoltmeter or to a data acquisition system with
input impedance higher than 4000 Ω. Normally, the output signal from the net
radiometer does not exceed ±20 mV. In order to grant the best performances
in measurements, the instrument resolution should be of 1μV.
Maintenance:
In order to ensure a high measurement accuracy, it is necessary to keep the to
keep the two receiving surfaces clean, the higher the frequency of cleaning, the
best measurement accuracy will be.
Cleaning can be done with normal tissue for the cleaning of lens and water, if not
enough, just use pure ethyl alcohol. After cleaning with alcohol it is necessary to
clean the domes again with water only.
We strongly recommend to calibrate LP NET 07 annually. The calibration can be
carried out by comparison with another net-radiometer sample in the field. The
field calibration is less precise than a calibration performed in the laboratory
but has the advantage of not having to remove the instrument from its housing.
Calibration and measurements:
Net radiometer sensitivity, indicated as S (or calibration factor), allows
determining the net radiant flow passing through a surface. S factor is
measured in μV/(Wm-2).
• Measured the potential difference (DDP) at the ends of the flow probe is
obtained by the following formula Ee
Ee= DDP/S
where;
Ee: indicates the radiant flux expressed in W/m2,
DDP: indicates the potential difference expressed in μV and measured by the
multimeter,
S: indicates the calibration factor expressed in μV/(W/m2) and shown on the
net radiometer label (calibration factor is also mentioned in the calibration
report).
N.B. If the difference of potential (DDP) is positive, the radiation on the upper
surface is higher than the radiation on the lower surface (typically during
daylight hours); if DDP is negative, the radiation on the lower surface is
higher that the one on the upper surface (typically at night).
Each net-radiometer is individually calibrated at the factory and is distinguished
by its calibrator factor.
Calibration is performed inside Delta Ohm Metrological Laboratory and
performed with a net radiometer-reference with a solar simulator as the
source of light. Calibration is performed with a beam of light in parallel.
Sensitivity to wind speed:
At the same radiant flux, by increasing the wind speed decreases the net
radiometer output signal will (sensitivity decrease by increasing wind speed).
Measurements taken inside the wind tunnel, have shown that Sv sensitivity,
related to the wind speed for LP NET 07, can be corrected by using the following
functions:
Sv=S0(1-0.011×V) per V≤10m/s
Sv=S0(0.95-0.006×V) per 10m/s<V<20m/s
Where: S0 = sensitivity at zero wind speed
V = wind speed in m/s
Fig. 2 shows the calibration factor related with wind speed.
Once we know both the net radiation – calculated through the sensitivity at zero

wind speed (Fnet_0) – and the wind speed in (V) in m/s, the correct data is obtained
by using the following formula:
Fnet=Fnet_0/(1-0.011×V) per V≤10m/s
Fnet=Fnet_0/(0.95-0.006×V) per 10m/s<V<20m/s
Cosine response/Directional error:
The radiation falling on a surface should be measured with a sensor, whose
response related to the light incidence angle, has to be a Lambertian Response.
A receiver is known as Lambertian when its sensibility (Sϑ), related to the
incidence angle between the light and the detector surface, has the following
behavior:
Sϑ=S0 cos(ϑ)
Where: S0 is the sensitivity when light strikes perpendicular to the surface, ϑ is
the angle between the incident light beam and the line which is normal to the
surface.
Fig. 3 shows the typical behaviour of the error related to the angle of incidence.
Technical specifications:
Typical sensitivity: 10 μV/(W/m2)
Impedance: 2Ω ÷ 4Ω
Measuring range: ±2000 W/m2
Spectral range: 0.2 μm ÷100 μm
Operating temperature: -40 °C ÷ 80 °C
Weight: 0.35 Kg
Response time (95%): <75 sec
ORDERING CODE
LP NET 07: Net radiometer. Connecting cable: 5 m standard length, complete
with Ø 16×500 rod for attachment to a mast Different cable lengths upon
request.
HD978TR3: Configurable signal converter amplifier with 4÷20mA (20÷4mA)
output. Input measuring range -10..+60mV. Default setting 0÷20mV.
2-module DIN housing. Minimum measuring range 2mV.
HD978TR5: Wall configurable, signal converter amplifier with 4÷20mA
(20÷4mA) output. Input measuring range –10…+60mV. Default settings
0÷20mV. Minimum measuring range 2mV. Wall mouting, dimensions:
58mmx65mmx35mm height.
HD978TR4:Configurable signal converter amplifier with 0÷10 Vdc (10÷0Vdc)
output.
Input measuring range -10..+60mV. Default setting 0÷20mV.
Minimum measuring range 2mV. 2-module DIN housing.
HD978TR6: Wall configurable, signal converter amplifier with 0÷10 Vdc
(10÷0Vdc) output. Input measuring range –10…+60mV. Default settings
0÷20mV. Minimum measuring range 2mV. Wall mouting, dimensions:
58mmx65mmx35mm height.

 

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Manuals and Brochures here.  

LPNET07.pdf

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