GHM Delta OHM LPPIRG01 User manual

Operating manual
Pyrgeometer
LPPIRG01
www.deltaohm.com
English
Keep for future reference.
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LPPIRG01 -2-V2.1
TABLE OF CONTENTS
1INTRODUCTION.................................................................................................... 3
2WORKING PRINCIPLE........................................................................................... 4
3INSTALLATION ..................................................................................................... 6
4ELECTRICAL CONNECTIONS.................................................................................. 9
4.1 LPPIRG01 CONNECTIONS...................................................................................... 9
4.2 LPPIRG01S CONNECTIONS.................................................................................. 10
5MEASUREMENT IN THE MODEL WITH ANALOG OUTPUT...................................... 11
6RS485 MODBUS-RTU OUTPUT............................................................................. 13
6.1 SETTING THE COMMUNICATION PARAMETERS............................................................... 13
6.2 READING THE MEASURES WITH THE MODBUS-RTU PROTOCOL .......................................... 15
7MAINTENANCE.................................................................................................... 16
8TECHNICAL SPECIFICATIONS............................................................................. 17
9SAFETY INSTRUCTIONS...................................................................................... 18
10 ORDERING CODES .............................................................................................. 19

LPPIRG01 -3-V2.1
1INTRODUCTION
LPPIRG01 pyrgeometer measures the far infrared radiation (FIR). The measures are
referred to radiations with wavelength greater than 4.5 µm.
The far infrared radiation derives from the measure of the thermopile output signal and
from the knowledge of the instrument temperature. The temperature is measured with
a 10 kΩNTC inserted in the body of the pyrgeometer.
The pyrgeometer can be used also for energy balance studies. In this case, besides
another pyrgeometer which measures infrared radiation upwards, it is necessary an
albedometer (LPPYRA05, LPPYRA06 or LPPYRA11) for measuring the short wavelengths
radiation (<3 µm).
The pyrgeometer is available in the following versions:
•LPPIRG01: Passive
•LPPIRG01S: With RS485 Modbus-RTU output.
The pyrgeometer is supplied factory calibrated and with a calibration report. The cali-
bration is carried out outdoors, for comparison with a reference standard pyrgeometer
calibrated at WRC (World Radiation Center). The two instruments are kept outdoors for
at least one night in the presence of clear sky. The data acquired by a data logger are
then processed to obtain the calibration factor.

LPPIRG01 -4-V2.1
2WORKING PRINCIPLE
LPPIRG01 pyrgeometer is based on a thermopile sensor. The thermopile sensitive sur-
face is coated with a black matt paint, which allows the pyrgeometer not to be selective
at different wavelengths.
The sensor is covered by a silicon window that has two basic purposes:
1. protect the thermopile from bad weather;
2. determine the instrument spectral range: silicon is transparent to wavelengths
longer than 1.1 µm, therefore on the inside of the window there is a filter to block
radiation up to 4.5 - 5 µm. The silicon external surface, which is exposed to weather
agents, has a scratch-resistant coating (DLC) to ensure strength and durability in
all weather conditions. The scratch-resistant coating offers the advantage of clean-
ing the surface without the risk of scratching the window. The transmission of the
silicon window as the wavelength varies is shown in figure 2.1.
1.
Fig. 2.1: Transmission of the silicon window
Radiant energy is absorbed/radiated by the thermopile black surface, thus creating a
difference of temperature between the center of the thermopile (hot junction) and the
pyrgeometer body (cold junction). Thanks to the Seebeck effect, the difference of tem-
perature between hot and cold junction is converted into a Difference of Potential.
If the pyrgeometer temperature is higher than the radiant temperature of the portion
of sky framed by the pyrgeometer, the thermopile will irradiate energy and the output
signal will be negative (typical situation of clear sky); vice versa, if the pyrgeometer
temperature is lower than that portion of sky framed, the signal will be positive (typical
situation of cloudy sky).
Therefore, for the calculation of infrared radiation at ground level (EFIR ↓), besides the
thermopile output signal, it is necessary to know the temperature of the pyrgeometer,
as shown in formula 1:

LPPIRG01 -5-V2.1
EFIR ↓= Eterm + σTB4(1)
Where:
Eterm =net radiation (positive or negative) measuredby the thermopile (W m-2);
σ= Stefan-Boltzmann constant (5.6704 x 10-8 W m-2 K-4);
TB= pyrgeometer temperature (K), obtained by the reading of the NTC resistance (see
table 5.1).
Eterm is calculated from the sensitivity of the instrument C[µV/(W m-2)] and from the
output signal Uemf according to formula 2:
Eterm = Uemf / C (2)
The first term of formula 1 represents the net radiation, that is to say the difference
between ground infrared radiation and the pyrgeometer emission, while the second term
is the radiation emitted by an object (assuming emissivity ε=1) at temperature TB.
Fig. 2.2: scheme of principle LPPIRG01 (version with mV output)
To prevent internal condensation forming on the internal side of the window under cer-
tain climatic conditions, silica gel tablets are inserted inside the pyrgeometer to absorb
humidity.
Thermopile
Surge
Protector
Connector pins
Housing
Cable
shield
NTC

LPPIRG01 -6-V2.1
3INSTALLATION
Before installing the pyrgeometer, refill the cartridge containing silica-gel crystals. Sil-
ica-gel absorbs humidity inside the instrument and prevents, in particular climatic con-
ditions, condensation on the internal surface of the silicon window 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 pyrgeometer).
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 pyrgeometer 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 pyrgeometer is ready for use.
The figure below shows the operations necessary to fill 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

LPPIRG01 -7-V2.1
•The pyrgeometer must be mounted in an easy-to-reach location in order to clean the
silicon window regularly. At the same time, make sure that no buildings, construc-
tions, trees or obstructions exceed the horizontal plane where the pyrgeometer lies.
If this is not possible, select a site where obstructions do not exceed 10°.
•In compliance with ISO TR9901 standard and WMO recommendations, when the
pyrgeometer is used without the white shade disk, it 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. In any case,
it is better to follow this suggestion even when the shade disk is applied.
•For fixing, use the holes on the pyrgeometer body (remove the shade disk to access
the holes and reposition it after mounting) or the suitable accessories (see the fig-
ures below). In order to allow an accurate horizontal positioning, the pyrgeometer is
equipped with a levelling device: the adjustment is made by means of the two level-
ling screws that allow adjusting the pyrgeometer inclination.
•It is preferably to thermally insulate the pyrgeometer from its mounting bracket en-
suring, at the same time, a good electrical contact to ground.
Fig. 3.2: fixing holes and levelling device
Fixing holes ∅6 mm
Levelling device

LPPIRG01 -8-V2.1
Fig. 3.3: fixing accessories

LPPIRG01 -9-V2.1
4ELECTRICAL CONNECTIONS
The pyrgeometer has a 8-pole connector and uses the CPM12AA8PG... (LPPIRG01) or
CPM12-8D... (LPPIRG01S) optional cables in UV resistant PTFE, with 8-pole connector
on one side and open wires on the other side.
The metallic housing of the pyrgeometer 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
pyrgeometer, connect the wire of the cable corresponding to the
housing to ground ( ).
The wire of the cable corresponding to the housing depends on the model: white wire
in LPPIRG01 and black wire (cable shield) in LPPIRG01S.
4.1 LPPIRG01 CONNECTIONS
The pyrgeometer LPPIRG01 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 pyr-
geometer output signal absolute value does not exceed 4 mV. In order to better exploit
the pyrgeometer features, the readout instrument should have 1 µV resolution.
To determine the pyrgeometer temperature, the NTC resistance must be read.
Connector Function Color
1
Vout (+)
Red
2
Vout (-)
Blue
3
Housing
White
4
NTC
Green
5
Cable shield
Brown
6
Not connected
7
Not connected
8
NTC
Black
Fig. 4.1: LPPIRG01connections
CPM12AA8PG… cable
Sensor M12
male connector
Datalogger
or
converter/amplifier
with Vor mA output
Red [1]
Blue [2]
Green [4]
White [3]
Connect to ground only if it is not possible to
ground locally the case of the pyrgeometer
Black [8]
Brown [5]
Ohmmeter

LPPIRG01 -10 -V2.1
4.2 LPPIRG01S CONNECTIONS
The pyrgeometer LPPIRG01S has RS485 Modbus-RTU output and requires 5…30 Vdc
external power supply. It is to be connected to a power supply and to a PLC, a data
logger or a RS485/USB or RS485/RS232 converter for PC as shown in fig. 4.2. The
RS485 output is not isolated.
Connector Function Color
1
Power supply negative (GND)
Blue
2
Power supply positive (+Vdc)
Red
3
Not connected
4
RS485 A/-
Brown
5
RS485 B/+
White
6
Housing
Shield (Black)
7
Not connected
8
Not connected
Fig. 4.2: LPPIRG01S connections
Before connecting the pyrgeometer to the RS485 network, set the address and the com-
munication parameters, if different from the factory preset (see chapter 6).
Pyrgeometer
Surge
Protector
Housing
RS485
output
Power supply
Power supply
5…30 Vdc
Red
Blue
Brown
White
CPM12-8D… cable
Sensor M12
male connector
PLC, data logger or
RS485/USB or
RS485/RS232
converter for PC
Other sensors with
RS485 output
Termination
Termination
Shield
Red
Connect to ground only if it is not possible
to ground locally the case of the pyranometer

LPPIRG01 -11 -V2.1
5MEASUREMENT IN THE MODEL WITH ANALOG OUTPUT
Measure the NTC resistance RNTC (Ω) and calculate the pyrgeometer temperature TB(K)
by using the formula 3:
1
TB= a+ blog(RNTC) + clog(RNTC)3(3)
Where:
a= 10297.2 x 10-7
b= 2390.6 x 10-7
c= 1.5677 x 10-7
The temperature is expressed in Kelvin.
Table 5.1 indicates the correspondence between TBand RNTC for temperature values
between -25 °C and +58 °C. To obtain the temperature value in Kelvin, add 273.15 to
the temperature value in degrees Celsius in the table.
TAB. 5.1: correspondence between pyrgeometer temperature and NTC resistance
TB(°C) RNTC (Ω) TB(°C) RNTC (Ω) TB(°C) RNTC (Ω)
-25 103700 3 25740 31 7880
-24 98240 4 24590 32 7579
-23 93110 5 23500 33 7291
-22 88280 6 22470 34 7016
-21 83730 7 21480 35 6752
-20 79440 8 20550 36 6499
-19 75390 9 19660 37 6258
-18 71580 10 18810 38 6026
-17 67970 11 18000 39 5804
-16 64570 12 17240 40 5592
-15 61360 13 16500 41 5388
-14 58320 14 15810 42 5193
-13 55450 15 15150 43 5006
-12 52740 16 14520 44 4827
-11 50180 17 13910 45 4655
-10 47750 18 13340 46 4489
-9 45460 19 12790 47 4331
-8 43290 20 12270 48 4179
-7 41230 21 11770 49 4033
-6 39290 22 11300 50 3893
-5 37440 23 10850 51 3758
-4 35690 24 10410 52 3629
-3 34040 25 10000 53 3505
-2 32470 26 9605 54 3386
-1 30980 27 9228 55 3386
0 29560 28 8868 56 3271
1 28220 29 8524 57 3161
2 26950 30 8195 58 3055

LPPIRG01 -12 -V2.1
Once the pyrgeometer temperature TBin Kelvin and the thermopile output signal Uemf
in µV (measured with a multimeter) are known, irradiation EFIR ↓(W m-2) is obtained
from the formula 4:
EFIR ↓= Uemf
C+ σTB4(4)
Where:
σ= Stefan-Boltzmann constant (5.6704 x 10-8 W m-2 K-4);
TB= sensitivity of the instrument expressed in µV/(Wm-2) and shown in the label on
the pyrgeometer (and in the calibration report).

LPPIRG01 -13 -V2.1
6RS485 MODBUS-RTU OUTPUT
Before connecting the pyrgeometer to the RS485 network, an address must be assigned
and the communication parameters must be set, if different from the factory preset.
6.1 SETTING THE COMMUNICATION PARAMETERS
Connect the pyrgeometer to the PC in one of the following two ways:
A. By using the optional CP24 cable, with built-in RS485/USB converter. In this con-
nection mode, the sensor is powered by the PC USB port. To use the cable, it is
necessary to install the related USB drivers in the PC.
B. By using the supplied 8-pole M12 female connector or the optional CPM12-8D…
cable and a generic RS485/USB or RS485/RS232 converter. In this connection mode,
it is necessary to power the pyrgeometer separately. If a RS485/USB converter is
used, it is necessary to install the related USB drivers in the PC.
NOTES ON THE INSTALLATION OF UNSIGNED USB DRIVER: before installing unsigned USB driver into
operating systems starting from Windows 7, it is necessary to restart the PC by disabling the driver
signing request. If the operating system is 64-bit, even after installation the request of driver
signing have to be disabled each time the PC is restarted.
Procedure:
1. Start with the pyrgeometer not powered (if the CP24 cable is used, disconnect one
end of the cable).
2. In the PC, start a serial communication program. Set the Baud Rate to 57600 and
set the communication parameters as follows (the pyrgeometer is connected to a
COM type port):
Data Bits: 8
Parity: None
Stop Bits: 2
In the program, set the COM port number to which the pyrgeometer will be con-
nected.
3. Switch the pyrgeometer on (if the CP24 cable is used, connect both ends of the cable).
Power supply
or
CPM12-8D… cable
Red
Blue
Brown
White
Pyrgeometer
connector
CP24 cable
Pyrgeometer
connector

LPPIRG01 -14 -V2.1
4. Within 10 seconds from the pyrgeometer power on, send the @command and press
Enter.
Note: if the pyrgeometer does not receive the @command within 10 seconds from
power on, the RS485 MODBUS mode is automatically activated. In such a case, it is
necessary to switch off and on again the pyrgeometer.
5. Send the command CAL USER ON.
Note: the command CAL USER ON is disabled after 5 minutes of inactivity.
6. Send the serial commands given in the following table to set the RS485 MODBUS
parameters:
Command
Response
Description
CMAnnn
&|
Set RS485 address to nnn
Ranging from 1 to 247
Preset on 1
CMBn
&|
Set RS485 Baud Rate
n=0 ⇒9600
n=1 ⇒19200
Preset on 1 ⇒19200
CMPn
&|
Set RS485 transmission mode
n=0 ⇒8-N-1 (8 data bits, no parity, 1 stop bit)
n=1 ⇒8-N-2 (8 data bits, no parity, 2 stop bits)
n=2 ⇒8-E-1 (8 data bits, even parity, 1 stop bit)
n=3 ⇒8-E-2 (8 data bits, even parity, 2 stop bits)
n=4 ⇒8-O-1 (8 data bits, odd parity, 1 stop bit)
n=5 ⇒8-O-2 (8 data bits, odd parity, 2 stop bits)
Preset on 2 ⇒8-E-1
CMWn
&|
Set receiving mode after RS485 transmission
n=0 ⇒Violate protocol and go in Rx mode right after Tx
n=1 ⇒Respect protocol and wait 3.5 characters after Tx
Preset on 1
⇒
Respect the protocol
7. You can check the parameters setting by sending the following serial commands:
Command
Response
Description
RMA
Address
Read RS485 address
RMB
Baud Rate
(0,1)
Read RS485 Baud Rate
0 ⇒9600
1 ⇒19200
RMP
Tx Mode
(0,1,2,3,4,5)
Read RS485 transmission mode
0 ⇒8-N-1
1 ⇒8-N-2
2 ⇒8-E-1
3 ⇒8-E-2
4 ⇒8-O-1
5 ⇒8-O-2
RMW
Rx Mode
(0,1)
Read receiving mode after RS485 transmission
0 ⇒Violate protocol and go in Rx mode right after Tx
1 ⇒Respect protocol and wait 3.5 characters after Tx
Note: it is not required to send the CAL USER ON command to read the settings.

LPPIRG01 -15 -V2.1
6.2 READING THE MEASURES WITH THE MODBUS-RTU PROTOCOL
In MODBUS mode, you can read the values measured by the pyrgeometer through the
function code 04h (Read Input Registers). The following table lists the quantities avail-
able with the appropriate register address:
Number
Address
Quantity
Format
1 0 Temperature in °C (x10) 16-bit Integer
2 1 Temperature in °F (x10) 16-bit Integer
3 2 Solar radiation in W/m216-bit Integer
4 3 Status register:
bit0=1 ⇒solar radiation measurement error
bit2=1 ⇒configuration data error
bit3=1 ⇒program memory error
16-bit Integer
5 4 Average values of the last 4 measurements 16-bit Integer
6 5 Signal generated by the sensor in µV/10
[e.g.: 816 means 8160 µV, the resolution is 10 µV]16-bit Integer
Note: Register address = Register number - 1, as defined in the Modbus standard.
OPERATING MODE: the pyrgeometer enters RS485 MODBUS-RTU mode after 10 seconds
from power on. In the first 10 seconds from power on the pyrgeometer does not reply
to requests from the MODBUS master unit. After 10 seconds, it is possible to send
MODBUS requests to the pyrgeometer.

LPPIRG01 -16 -V2.1
7MAINTENANCE
In order to grant measurements high accuracy, it is important to keep the silicon win-
dow clean. Consequently, the more the dome will be kept clean, the more measure-
ments will be accurate.
You can wash it using water and standard papers for lens. If necessary, use pure ETHYL
alcohol. After using alcohol, clean again the silicon window with water only.
Because of the high temperature changes between day and night, some condensation
might appear inside the pyrgeometer (especially on the silicon window). In this case
the performed reading is wrong. To minimize the condensation, the pyrgeometer is
provided with a cartridge containing dessicant material (silica-gel). The efficiency of the
silica-gel crystals decreases over time while absorbing humidity. Silica-gel crystals are
efficient when their color is yellow, while they turn white/translucent as soon as
they lose their efficiency. Read instructions at chapter 3 about how to replace the silica-
gel crystals. Silica-gel typical lifetime goes from 2 to 6 months depending on the envi-
ronment where the pyrgeometer works.
Hail of particular intensity/size may damage the silicon window; therefore, it is recom-
mended to check the status of the window after an intense storm with hail.
To exploit all the pyrgeometer features, it is highly recommended that the calibration
be checked annually.

LPPIRG01 -17 -V2.1
8TECHNICAL SPECIFICATIONS
Sensor Thermopile
Typical sensitivity 5÷10 µV/Wm-2
Impedance 33÷45 Ω
Measuring range -300÷+300 W/m2
Viewing angle 160°
Spectral range (50%)
(transmission of the silicon window) 5.5÷45 µm
Operating temperature -40÷80 °C
Output Analog in µV/Wm-2 (LPPIRG01)
Digital RS485 Modbus-RTU (LPPIRG01S)
Power supply 5÷30 Vdc (LPPIRG01S)
Connection 8-pole M12 connector
Dimensions Fig. 3.2
Weight 0.9 kg
Accuracy of levelling device < 0.1°
Protection degree IP 67
MTBF > 10 years
Technical Specifications According to ISO 9060:2018
Response time (95%) < 28 s
Zero offset (type B)
a) response to a 5 K/h change in am-
biente temperature <±4W/m2
Long-term instability (1 year) <±1.5%
Non-linearity <±1%
Spectral selectivity < ±5%
Temperature response < 3 %
Tilt response <±2%

LPPIRG01 -18 -V2.1
9SAFETY INSTRUCTIONS
General safety instructions
The instrument has been manufactured and tested in accordance with the safety stand-
ard EN61010-1:2010 “Safety requirements for electrical equipment for measurement,
control and laboratory use” and has left the factory in perfect safety technical condi-
tions.
The instrument proper operation and operating safety can be ensured only if all stand-
ard safety measures as well as the specific measures described in this manual are fol-
lowed.
The instrument proper operation and operating safety can be ensured only in the cli-
matic conditions specified in this manual.
Do not use the instruments in places where there are:
•Corrosive or flammable gases.
•Direct vibrations or shocks to the instrument.
•High-intensity electromagnetic fields, static electricity.
User obligations
The instrument operator shall follow the directives and regulations below that refer to
the treatment of dangerous materials:
•EEC directives on workplace safety.
•National law regulations on workplace safety.
•Accident prevention regulations.

LPPIRG01 -19 -V2.1
10 ORDERING CODES
LPPIRG01 Pyrgeometer. Complete with shade disk, cartridge for silica-gel
crystals, 2 spare sachets, levelling device, M12 8-pole connector
and Calibration Report. CPM12AA8PG… cable has to be or-
dered separately.
LPPIRG01SPyrgeometer. Complete with shade disk, cartridge for silica-gel
crystals, 2 spare sachets, levelling device, M12 8-pole connector
and Calibration Report. RS485 Modbus-RTU output. Power sup-
ply 5…30 Vdc. CPM12-8D… cable has to be ordered separately.
LPSP1UV-resistant shade disk.
LPS1 Fixing bracket for the pyrgeometer, suitable for ∅40 ÷ 50 mm
mast. Installation on horizontal or vertical mast.
HD2003.79K Kit to mount the pyrgeometer on ∅40 mm clamping. To install the
pyranometer on a transverse mast.
HD2003.85K Kit with adjustable height to mount the pyrgeometer on a ∅40 mm
mast.
CPM12AA8PG.2 Cable with 8-pole M12 connector on one end, open wires on the
other end. Length 2 m.
CPM12AA8PG.5 Cable with 8-pole M12 connector on one end, open wires on the
other end. Length 5 m.
CPM12AA8PG.10 Cable with 8-pole M12 connector on one end, open wires on the
other end. Length 10 m.
CPM12-8D.2 Cable with 8-pole M12 connector on one end, open wires on the
other end. Length 2 m.
CPM12-8D.5 Cable with 8-pole M12 connector on one end, open wires on the
other end. Length 5 m.
CPM12-8D.10 Cable with 8-pole M12 connector on one end, open wires on the
other end. Length 10 m.
CP24 PC connecting cable for the RS485 MODBUS parameters configura-
tion of the LPPIRG01S pyrgeometer. With built-in RS485/USB con-
verter. 8-pole M12 connector on instrument side and A-type USB
connector on PC side.
LPSG Cartridge to contain desiccant silica-gel crystals, complete with O-
ring and cap.
LPG Pack of 5 sachets of silica-gel crystals.
DELTA OHM metrology laboratories LAT N° 124 are ISO/IEC 17025 accredited by AC-
CREDIA for Temperature, Humidity, Pressure, Photometry / Radiometry, Acoustics
and Air Velocity. They can supply calibration certificates for the accredited quanti-
ties.

LPPIRG01 -20 -V2.1
NOTES