GHM DeltaOHM LPPYRA05 Manuel utilisateur

Operating manual

Albedometer

LPPYRA05

www.deltaohm.com

English

Keep for future reference.

LPPYRA05 - 2 - V2.2

TABLE OF CONTENTS

1 INTRODUCTION .................................................................................................... 3

2 WORKING RINCI LE ........................................................................................... 4

3 INSTALLATION ..................................................................................................... 5

4 ELECTRICAL CONNECTIONS .................................................................................. 7

5 MEASUREMENT ..................................................................................................... 8

6 MAINTENANCE ...................................................................................................... 9

7 TECHNICAL S ECIFICATIONS ............................................................................. 10

8 SAFETY INSTRUCTIONS ...................................................................................... 11

9 ORDERING CODES .............................................................................................. 12

LPPYRA05 - 3 - V2.2

1 INTRODUCTION

The LPPYRA05 albedometer measures the net global radiation, as well as the albedo o

grounds (albedo is the ratio between di use radiation rom a determined sur ace and

the quantity o radiation that arrives on the sur ace).

The LPPYRA05 is manu actured mounting two LPPYRA02 pyranometers in one housing

only. The two pyranometers, one measuring the incident radiation striking the ground

[ ↓ ] and the other one measuring the re lected radiation [ ↑ ], are combined in such a

way to have the same sensitivity.

The output signals o the two pyranometers can be processed to get the desired phys-

ical quantity.

The LPPYRA05 can be used as a pyranometer or measuring global radiation. As a py-

ranometer, the LPPYRA05 is a Spectrally Flat Class B (First Class) pyranometer in ac-

cordance with ISO 9060:2018 and with the criteria o the WMO “Guide to Meteorologi-

cal Instruments and Methods o Observation”.

The albedometer is supplied actory calibrated and with a calibration report. The cali-

bration is carried out in accordance with the ISO 9847:1992 (type IIc) standard: ”Cal-

ibration o ield pyranometers by comparison to a re erence pyranometer”. The pyra-

nometer is calibrated by comparison with the re erence sample calibrated annually at

WRC (World Radiation Center).

LPPYRA05 - 4 - V2.2

2WORKING RINCI LE

The LPPYRA05 albedometer is based on a pair o thermopile sensors, one o them

measuring the incident radiation on the ground [ ↓ ] and the other one the re lected

radiation [ ↑ ]. Each thermopile works as an independent pyranometer. The thermo-

pile sensitive sur ace is coated with a black matt paint, which allows the pyranometer

not to be selective at di erent wave lengths. The pyranometer spectral range is de-

termined by the transmission o the two glass domes type K5.

Radiant energy is absorbed by the thermopile black sur ace, thus creating a di erence

o temperature between the center o the thermopile (hot junction) and the pyranom-

eter body (cold junction). Thanks to the Seebeck e ect, the di erence o temperature

between hot and cold junction is converted into a Di erence o Potential.

In order to grant the thermopile a proper thermal insulation rom the wind and reduce

the sensitivity to thermal irradiance, LPPYRA05 is equipped with two concentric domes

having 50 mm and 32 mm outer diameter on each side. The domes protect the ther-

mopile rom the dust, which might change spectral sensitivity i it lies on the black

sur ace.

To prevent internal condensation orming on the internal side o the dome under cer-

tain climatic conditions, silica gel tablets are inserted inside the pyranometer to ab-

sorb humidity.

Fig. 2.1: scheme of principle L YRA05

The resistance inserted in parallel to the thermopile allows to obtain the same calibra-

tion actor or both sensors.

ermopil

Surge

Protector

Connector

pins

Housing

To cable shield

ermopil

Surge

Protector

LPPYRA05 - 5 - V2.2

3INSTALLATION

Be ore installing the albedometer, re ill the cartridge containing silica-gel crystals. Sili-

ca gel absorbs humidity in the dome chamber and prevents, in particular climatic con-

ditions, condensation on the internal walls o the domes and measurement alteration.

Do not touch the silica gel crystals with your hands while re illing the cartridge. Carry

out the ollowing instructions in an environment as drier as possible:

1. Loosen the three screws that ix the white shade disk.

2. Unscrew the silica gel cartridge using a coin.

3. Remove the cartridge per orated cap.

4. Open the sachet containing silica gel (supplied with the pyranometer).

5. Fill the cartridge with 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 pyranometer body using a coin.

8. Check that the cartridge is screwed tightly (i not, silica gel li e will be reduced).

9. Position the shade disk and screw it with the screws.

10. The albedometer is ready or use.

The igure below shows the operations necessary to ill the cartridge with the silica gel

crystals.

Fig. 3.1: filling the silica-gel cartridge

Silica

gel

cartridge

Perforated cap

Sealed sachet

of silica-gel crystals

Filling Closing the cartridge

LPPYRA05 - 6 - V2.2

•Mount the albedometer 1 – 2 m above the ground. Grass should be kept at the

same height all the year long. In snowy regions, keep the instrument above the

blanket o snow so that the distance rom the albedometer to the snow be constant.

•The albedometer must be mounted in an easy-to-reach location in order to clean

the dome regularly and carry out maintenance. At the same time, make sure that

no buildings, constructions, trees or obstructions exceed the horizontal plane where

the upper pyranometer lies. I this is not possible, select a site where obstructions

in the path o the sun rom sunrise to sunset do not exceed 5 degrees o elevation.

N.B.: The presence of obstructions on the horizon line affects significantly

the measurement of direct irradiance.

•The pyranometer must be located ar rom any kind o obstruction, which might re-

lect sunlight (or sun shadow) onto the pyranometer itsel .

•In compliance with ISO TR9901 standard and WMO recommendations, when the

pyranometer is used without the white shade disk, it must be positioned so that its

connector is pointed to the North Pole, i the instrument is used in the Northern

Hemisphere, and to the South Pole, i used in the Southern Hemisphere. In any

case, it is better to ollow this suggestion even when the shade disk is applied.

•The mounting can be made using the rod provided with the instrument. In order to

allow an accurate horizontal positioning, the pyranometer is equipped with a level-

ling device. The mast height does not exceed the pyranometer plane to avoid

measurement errors caused by any re lection or shadow o the mast itsel .

•It is pre erably to thermally insulate the pyranometer rom its mounting bracket

ensuring, at the same time, a good electrical contact to ground.

79.5

500

140

160

124

Fig. 3.2: fixing and dimensions

Connector

Levelling device

LPSP1

LPSP3

LPPYRA05 - 7 - V2.2

4ELECTRICAL CONNECTIONS

L YRA05 has a 8-pole connector and uses the C M12AA8... optional cables, with

8-pole connector on one side and open wires on the other side.

The metallic housing of the albedometer should preferably be

grounded ( ) locally. In this case, do not connect the wire of the

cable corresponding to the housing to prevent ground loops.

Only if it is not possible to ground locally the metallic case of the

albedometer, connect the wire of the cable corresponding to the

housing to ground ( ).

The albedometer LPPYRA05 is passive and does not require power supply. It is to be

connected either to a millivoltmeter or to a data acquisition system (with at least two

inputs). Typically, the albedometer output signal does not exceed 20 mV. In order to

better exploit the albedometer eatures, the readout instrument should have 1 µV res-

olution.

Connector Function Color

1 Output positive (+Vout) upper pyranometer [↓] Red

2 Output negative (-Vout) upper pyranometer [↓] Blue

3 Not connected

4 Not connected

5 Output negative (-Vout) lower pyranometer [↑] Brown

6 Housing (C) White

7 Cable shield (SH) Black

8 Output positive (+Vout) lower pyranometer [↑] Green

456

+Vout [ ]

-Vout [ ]

+Vout [ ]¯

-Vout [ ]¯

Fig. 4.1: L YRA05 connections

The cable shield is isolated rom the albedometer housing by means o two gas surge

arrestors, which prevents lightnings to damage the sensor. The shield has to be con-

nected to the same ground as the readout instrument. Best sa ety is achieved through

a per ect connection between housing and earth.

Connect to ground only if it is not possible to

ground locally the case of the pyranometer

CPM12AA8… cable

Albedometer

M12 male

connector

Reflected

radiation [↑]

ncident

radiation [↓]

Multi

input

data

logger

Converter

amplifier

with V or mA

output

Converter

amplifier

with V or mA

output

LPPYRA05 - 8 - V2.2

5MEASUREMENT

Each albedometer is distinguished by its own sensitivity (or calibration actor) S ex-

pressed in µV/(Wm-2) and shown in the label on the albedometer (and in the calibra-

tion report).

The sensitivity S is the same or both pyranometers.

The irradiance Ee is obtained by measuring with a multimeter the di erence o potential

DDP at the ends o the sensor and applying the ollowing ormula:

Ee = DDP / S

where:

Ee is the irradiance expressed in W/m2;

DDP is the di erence o potential expressed in µV measured by the multimeter;

S is the sensitivity o the albedometer expressed in µV/(Wm-2).

Albedo is the raction o solar radiation that is re lected rom the ground, with respect

to incident radiation:

ALBEDO = Ee [↑] / Ee [↓]

With the albedometer it is possible to calculate the net radiation making the di erence

between the incident global radiation and the re lected global radiation.

LPPYRA05 - 9 - V2.2

6MAINTENANCE

In order to grant measurements high accuracy, it is important to keep the outer glass

domes clean. Consequently, the more the domes will be kept clean, the more meas-

urements will be accurate.

You can wash it using water and standard papers or lens. I necessary, use pure

ETHYL alcohol. A ter using alcohol, clean again the domes with water only.

Because o the high temperature changes between day and night, some condensation

might appear on the domes o the pyranometers. In this case the per ormed reading

is highly over-estimated. To minimize the condensation, the albedometer is provided

with a cartridge containing dessicant material (silica-gel). The e iciency o the silica-

gel crystals decreases over time while absorbing humidity. Silica-gel crystals are e i-

cient when their color is yellow, while they turn white/translucent as soon as they

loose their e iciency. Read instructions at chapter 3 about how to replace the silica-

gel crystals. Silica-gel typical li etime goes rom 2 to 6 months depending on the envi-

ronment where the albedometer works.

To exploit all the albedometer eatures, it is highly recommended that the calibration

be checked annually.

LPPYRA05 - 10 - V2.2

7TECHNICAL S ECIFICATIONS

Sensor Thermopile

Typical sensitivity 6÷12 µV/Wm-2

Impedance 33÷45 Ω

Measuring range 0÷2000 W/m2

Viewing angle 2π sr

Spectral range (50%) 283÷2800 nm

Operating temperature/humidity -40÷80 °C / 0÷100%

Output Analog in µV/Wm-2

Connection 8-pole M12 connector

Dimensions Fig. 3.2

Weight 1.35 kg approx. (complete albedometer)

Accuracy of levelling device < 0.1°

rotection degree IP 67

MTBF > 10 years

Technical Specifications According to ISO 9060

Classification Spectrally Flat Class B

Response time (95%) < 10 s

Zero offset

a) response to a 200 W/m2 thermal

radiation

<±10W/m2

b) response to a 5 K/h change in

ambiente temperature

<±4W/m2

c) total zero offset including the

effects a), b) and other sources

<±15W/m2

Long-term instability (1 year) <±1 %

Non-linearity <±1 %

Response according to the cosine law <±18 W/m2

Spectral error < ±0.5 %

Temperature response (-10…+40°C) < 1.5 %

Tilt response <±2 %

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