GHM DeltaOHM LPPYRA-Lite User manual

Operating manual
Pyranometer
LPPYRA
-Lite
www.deltaohm.com
English
Keep for future reference.

LPPYRA-Lite -2-V1.1
TABLE OF CONTENTS
1INTRODUCTION.................................................................................................... 3
2WORKING PRINCIPLE........................................................................................... 4
3INSTALLATION ..................................................................................................... 5
4ELECTRICAL CONNECTIONS.................................................................................. 8
4.1 LPPYRA-LITE CONNECTIONS .................................................................................. 8
4.2 LPPYRA-LITEAC CONNECTIONS............................................................................... 9
5MEASUREMENT ................................................................................................... 10
5.1 LPPYRA-LITE .................................................................................................. 10
5.2 LPPYRA-LITEAC .............................................................................................. 10
6MAINTENANCE.................................................................................................... 11
7TECHNICAL SPECIFICATIONS............................................................................. 12
8SAFETY INSTRUCTIONS...................................................................................... 13
9ACCESSORIES ORDERING CODES ....................................................................... 14

LPPYRA-Lite -3-V1.1
1INTRODUCTION
LPPYRA-Lite pyranometer measures the irradiance on a flat surface (W/m2). The
measured irradiance (Global Irradiance) is the sum of direct solar irradiance and dif-
fuse irradiance.
LPPYRA-Lite is a Spectrally Flat Class C (Second Class) pyranometer in accordance
with ISO 9060:2018 and with the criteria of the WMO “Guide to Meteorological In-
struments and Methods of Observation’”.
The pyranometer is available in the following versions:
•LPPYRA-Lite: PASSIVE.
The passive version can be connected to the instruments
D09847 and HD31 by using VP472 SICRAM module.
•LPPYRA-LiteAC: ACTIVE with 2-wire (current loop) 4..20 mA output (0…2000
W/m2).
The pyranometer is supplied factory calibrated. The calibration is carried out in
accordance with the ISO 9847:1992 (type IIc) standard: ”Calibration of field
pyranometers by comparison to a reference pyranometer”. The pyranometer is
calibrated by comparison with the reference sample calibrated annually at WRC (World
Radiation Center).
An optional fixing base integrating a levelling device is available as an accessory, for
installations where horizontal positioning is required.

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2WORKING PRINCIPLE
LPPYRA-Lite 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 se-
lective at different wavelengths.
Radiant energy is absorbed by the thermopile black surface, thus creating a difference
of temperature between the center of the thermopile (hot junction) and the pyranom-
eter 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 reduce
the sensitivity to thermal irradiance, LPPYRA-Lite is equipped with a glass dome. The
dome protects the thermopile from the dust, which might change spectral sensitivity if
it lies on the black surface,
To prevent internal condensation forming on the internal side of 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 LPPYRA-Lite (version with mV output)
Thermopile
Connector pins
Housing

LPPYRA-Lite -5-V1.1
3INSTALLATION
•The pyranometer 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 pyranometer lies. If this is not possible, select a site where obstructions in the
path of the sun from sunrise to sunset do not exceed 5 degrees of elevation. N.B.:
The presence of obstructions on the horizon line affects significantly the
measurement of direct irradiance.
•The pyranometer must be located far from any kind of obstruction, which might re-
flect sunlight (or sun shadow) onto the pyranometer itself.
•In compliance with ISO TR9901 standard and WMO recommendations, the pyra-
nometer must be positioned so that its connector is pointed to the North Pole, if the
instrument is used in the Northern Hemisphere, and to the South Pole, if used in
the Southern Hemisphere.
•For fixing, use the two holes under the pyranometer body or the suitable accesso-
ries (see the figures below). In order to allow an accurate horizontal positioning,
the optional LPS40/32BL fixing base integrating a levelling device can be used.
The mast height does not exceed the pyranometer plane to avoid measurement er-
rors caused by any reflection or shadow of the mast itself.
•It is preferably to thermally insulate the pyranometer from its mounting bracket
ensuring, at the same time, a good electrical contact to ground.
•
Fig. 3.1: dimensions and fixing holes

LPPYRA-Lite -6-V1.1
LPS40/32
LPS40/32BL - Integrated levelling device
Fig. 3.2: fixing adapters from 40 to 32 mm holes centre distance
Fig. 3.3: fixing on HD2003.77/40 clamping
Fig. 3.4: fixing on LPS3 bracket
Levelling
device

LPPYRA-Lite -7-V1.1
Fig. 3.3: fixing on LPRING04 adjustable holder

LPPYRA-Lite -8-V1.1
4ELECTRICAL CONNECTIONS
LPPYRA-Lite has a 4-pole connector and uses the CPM12AA4... optional cables, with
4-pole connector on one side and open wires on the other side.
The metallic housing of the pyranometer 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
pyranometer, connect the wire of the cable corresponding to the
housing to ground ( ).
In the powered version LPPYRA-LiteAC, inside the housing there is a
surge protector connected between the housing itself and the elec-
tronic circuit. Grounding the housing allows the correc
t protection
function (in particular against lightning) of the surge protector.
4.1 LPPYRA-Lite CONNECTIONS
The pyranometer LPPYRA-Lite is passive and does not require power supply. It is 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 py-
ranometer features, the readout instrument should have 1 µV resolution.
Connector Function Color
1 +Vout Red
2
-Vout
Blue
3
Housing (C)
White
4
Cable shield (SH)
Black
Fig. 4.1: LPPYRA-Lite connections
CPM12AA4… cable
Pyranometer M12
male connector
Datalogger or
converter/amplifier
with Vor mA output
Connect to ground only if it is not possible to
ground locally the housing of the pyr
anometer
To circuit
Housing
Surge
protector

LPPYRA-Lite -9-V1.1
4.2 LPPYRA-LiteAC CONNECTIONS
The pyranometer LPPYRA-LiteAC has 4…20 mA output and requires 10…28 Vdc ex-
ternal power supply. It is to be connected to a power supply and an instrument with
4…20 mA input as shown in fig. 4.2. The load resistance of the instrument reading the
signal must be ≤500 Ω.
Connector Function Color
1
Positive (Iin)
Red
2
Negative (Iout)
Blue
3
Housing (C)
White
4
Cable shield (SH)
Black
Fig. 4.2: LPPYRA-LiteAC connections
CPM12AA4… cable
Pyranometer M12
male connector
Power supply
Connect to ground only if it is not possible to
ground locally the housing of the pyr
anometer
Instrument with
4…20 mA input

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5MEASUREMENT
Below are the ways to calculate the global irradiance.
5.1 LPPYRA-Lite
Each pyranometer is distinguished by its own sensitivity (or calibration factor) S ex-
pressed in µV/(Wm-2) and shown in the label on the pyranometer (and in the optional
calibration report).
The irradiance Eeis obtained by measuring with a multimeter the difference of potential
DDP at the ends of the sensor and applying the following formula:
Ee= DDP / S
where:
Eeis the irradiance expressed in W/m2;
DDP is the difference of potential expressed in µV measured by the multimeter;
Sis the sensitivity of the pyranometer expressed in µV/(Wm-2).
5.2 LPPYRA-LiteAC
The 4…20 mA output signal corresponds to the 0…2000 W/m2irradiance range.
The irradiance Eeis obtained by measuring with a multimeter the current Iout absorbed
by the sensor and applying the following formula:
Ee= 125 •(Iout - 4)
where:
Eeis the irradiance expressed in W/m2;
Iout is the current expressed in mA absorbed by the pyranometer.