GHM Delta OHM LPPYRA12 User manual

Operating manual
Pyran
ometer
LPPYRA
12
www.deltaohm.com
English
Keep for future reference.
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LPPYRA12 -2-V2.2
TABLE OF CONTENTS
1INTRODUCTION.................................................................................................... 3
2WORKING PRINCIPLE........................................................................................... 4
3INSTALLATION ..................................................................................................... 5
3.1 MOUNTING THE SHADOW RING ................................................................................6
3.2 POSITIONING THE INSTRUMENT FOR THE DIFFUSE RADIATION MEASUREMENT ...........................7
4ELECTRICAL CONNECTIONS................................................................................ 11
4.1 LPPYRA12 CONNECTIONS ..................................................................................11
4.2 LPPYRA12AC CONNECTIONS...............................................................................12
4.3 LPPYRA12AV CONNECTIONS............................................................................... 12
4.4 LPPYRA12S CONNECTIONS................................................................................. 13
4.5 LPPYRA12S12 CONNECTIONS .............................................................................14
5MEASUREMENT IN THE MODELS WITH ANALOG OUTPUT....................................15
5.1 LPPYRA12....................................................................................................15
5.2LPPYRA12AC................................................................................................15
5.3 LPPYRA12AV................................................................................................15
6RS485 MODBUS-RTU OUTPUT............................................................................. 16
6.1 SETTING THE COMMUNICATION PARAMETERS.............................................................. 16
6.2 READING THE MEASURES WITH THE MODBUS-RTU PROTOCOL..........................................18
7SDI-12 OUTPUT .................................................................................................. 19
8MEASUREMENT CORRECTION ............................................................................. 23
9MAINTENANCE.................................................................................................... 26
10 TECHNICAL SPECIFICATIONS............................................................................. 27
11 SAFETY INSTRUCTIONS...................................................................................... 28
12 ORDERING CODES .............................................................................................. 29

LPPYRA12 -3-V2.2
1INTRODUCTION
LPPYRA12 pyranometer measures the irradiance on a flat surface (W/m2). Thanks to
the shadow-ring, LPPYRA12 measures the diffuse solar radiation eliminating the con-
tribution of direct irradiance.
LPPYRA12 is equipped with a Spectrally Flat Class B (First Class) pyranometer (LPPY-
RA02) in accordance with ISO 9060:2018 and with the criteria of the WMO “Guide to
Meteorological Instruments and Methods of Observation”.
The pyranometer is available in the following versions:
•LPPYRA12: PASSIVE
The passive version can be connected to the instruments
D09847 and HD31 by using VP 472 SICRAM module.
•LPPYRA12AC: ACTIVE with 4..20 mA CURRENT output
•LP PYRA12AV: ACTIVE with 0..1 or 0..5 or 0..10 V VOLTAGE output to be de-
fined when ordering.
•LPPYRA12S: With RS485 Modbus-RTU output.
•LPPYRA12S12: With SDI-12 output.
The pyranometer is supplied factory calibrated and with a calibration report. The cali-
bration is carried out in accordance with the ISO 9847:1992 (type IIc) standard: ”Cal-
ibration of field pyranometers by comparison to a reference pyranometer”. The pyra-
nometer is calibrated by comparison with the reference sample calibrated annually at
WRC (World Radiation Center).

LPPYRA12 -4-V2.2
2WORKING PRINCIPLE
LPPYRA12 pyranometer is based on a thermopile sensor. The thermopile sensitive sur-
face is coated with a black matt paint, which allows the pyranometer not to be selec-
tive at different wavelengths. The pyranometer spectral range is determined by the
transmission of the two glass domes type K5.
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, LPPYRA12 is equipped with two concentric domes
having 50 mm and 32 mm outer diameter. The domes protect the thermopile from the
dust, which might change spectral sensitivity if it lies on the black surface.
The shadow ring prevents the direct solar radiation to reach the sensor the whole day
long, so that only the diffuse solar radiation will be measured. Because the elevation
of the sun changes day by day, it is necessary to change the height of the shad-
ow ring at least every two days.
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 LPPYRA12 (version with mV output)
Thermopile
Surge
Protector
Connector pins
Housing
To cable shield

LPPYRA12 -5-V2.2
3INSTALLATION
Before installing the pyranometer, refill the cartridge containing silica-gel crystals. Sil-
ica gel absorbs humidity in the dome chamber and prevents, in particular climatic
conditions, condensation on the internal walls of the domes and measurement altera-
tion.
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 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 (if not, silica gel life will be reduced).
9. Position the shade disk and screw it with the screws.
10. The pyranometer 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

LPPYRA12 -6-V2.2
•The pyranometer must be mounted in an easy-to-reach location in order to clean
the dome regularly and adjust the height of the shadow ring. At the same time,
make sure that no buildings, constructions, trees or obstructions exceed the hori-
zontal 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.
•The pyranometer must be located far from any kind of obstruction, which might al-
ter the measurement of diffused light.
•In order to allow an accurate horizontal positioning, the pyranometer is equipped
with a levelling device: the adjustment is made by means of the levelling screws
that allow adjusting the pyranometer inclination.
3.1 MOUNTING THE SHADOW RING
LPPYRA12 is made up of two parts: the pyranometer and the shadow ring.
Fig. 3.2: LPPYRA12 dimensions and description
To make the transport easier, the shadow ring is disassembled in the following pieces:
•Base (composed of three spokes).
•Shadow ring with “L” profile.
•Sliding bars with graduated scale.
•Pillar + crossbar + pyranometer support + goniometer (factory assembled and
aligned).
Mounting Instructions:
1. Screw the three spokes of the base to the pillar.
2. Screw the two sliding bars to the shadow ring.
3. Insert the sliding bars of the ring in the two slots at the crossbar ends (if correct-
ly mounted, the ring axis crosses the pyranometer thermopile center).
Levelling device
Screw with ring nut
Pillar
Crossbar
Graduated
sliding bar
Base
Pyranometer
support
Goniometer
Pyranometer
Shadow ring

LPPYRA12 -7-V2.2
3.2 POSITIONING THE INSTRUMENT FOR THE DIFFUSE RADIATION MEASUREMENT
The shadow ring particular geometry allows intercepting the solar direct radiation dur-
ing the whole day without adjustments.
The base of the instrument has to be mounted parallel to the ground by adjusting the
screw with ring nut and with the aid of the levelling device integrated in the instrument.
The shadow ring has to be positioned in such a way that its axis be parallel to the
earth axis. To do this, follow two separate steps: first align the shadow ring along the
North-South axis and then adjust the ring tilt.
Fig. 3.3: positioning the instrument
Aligning the shadow ring along the North-South axis:
1. Wait for solar midday.
2. On the goniometer where the pyranometer is mounted there is a groove, rotate the
shadow ring base until the sunbeams pass through the groove from both sides of
the goniometer.
Fig. 3.4: shadow ring North-South alignment
As you get closer to the equator, this method involves an increasing uncertainty. For
installations in sites nearby the equator, it is suggested to use a map to align the
shadow ring along the North-South axis.
Shadow ring axis
Earth axis
North Pole
South Pole
Equator
Solar radiation
Sunrays

LPPYRA12 -8-V2.2
Adjusting the shadow ring tilt:
1. Check that the sliding bars and the long side of the pyranometer support be parallel
(instruments are supplied factory aligned).
2. Mount and fix the pyranometer to the goniometer.
3. Position the goniometer in such a way to read on its scale the latitude of the instal-
lation site.
Fig. 3.5: shadow ring tilt adjustment
4. Rotate the crossbar (after loosening the screw that locks it) until the pyranometer
is parallel to the ground. Use the levelling device on the pyranometer body.
5. If the operations have been carried out properly, the shadow ring axis will be paral-
lel to the earth axis.
By now you just have to adjust the height of the sliding bars (loosening the locking
screws) until the pyranometer big dome appears completely in the shade. To confirm
that installation has been performed correctly, you can compare the reading on the
sliding bar scale with the value listed in tables 1A and 1B. If the values match, the py-
ranometer and the shadow ring have been correctly installed.
The shadow ring position has to be adjusted at least once every two days.
Angle reading

LPPYRA12 -9-V2.2
TABLE 1A
VALID ONLY FOR LPPYRA12 (no AC/AV/S/S12 versions)
The table shows the values to which the graduated sliding bars must be set for the
different solar declinations and for the two hemispheres.
Solar
declination Date
day/month
Value to be set on the
sliding bars (mm) if
installed in the
Northern hemisphere
Value to be set on the
sliding bars (mm) if
installed in the
Southern hemisphere
-23.26 21/12 101 121
-22 10/1 3/12 96 116
-20 21/1 22/11 87 107
-18 29/1 13/11 77 97
-16 5/2 6/11 68 88
-14 11/2 31/10 58 78
-12 17/2 25/10 49 69
-10 23/2 19/10 39 59
-8 28/2 14/10 29 49
-6 5/3 8/10 19 39
-4 10/3 3/10 10 30
-2 15/3 28/9 0 20
0 21/3 23/9 10 10
+2 26/3 18/9 20 0
+4 31/3 12/9 30 10
+6 5/4 6/9 39 19
+8 10/4 2/9 49 29
+10 16/4 27/8 59 39
+12 22/4 21/8 69 49
+14 28/4 15/8 78 58
+16 4/5 9/8 88 68
+18 12/5 1/8 97 77
+20 20/5 23/7 107 87
+22 31/5 12/7 116 96
+23.26 21/6 121 101

LPPYRA12 -10 -V2.2
TABLE 1B
VALID FOR LPPYRA12AC / LPPYRA12AV / LPPYRA12S / LPPYRA12S12
The table shows the values to which the graduated sliding bars must be set for the
different solar declinations and for the two hemispheres.
Solar
declination Date
day/month
Value to be set on the
sliding bars (mm) if
installed in the
Northern hemisphere
Value to be set on the
sliding bars (mm) if
installed in the
Southern hemisphere
-23.26 21/12 92 130
-22 10/1 3/12 87 125
-20 21/1 22/11 78 116
-18 29/1 13/11 68 106
-16 5/2 6/11 59 97
-14 11/2 31/10 49 87
-12 17/2 25/10 40 78
-10 23/2 19/10 30 68
-8 28/2 14/10 20 58
-6 5/3 8/10 10 48
-4 10/3 3/10 1 39
-2 15/3 28/9 9 29
0 21/3 23/9 19 19
+2 26/3 18/9 29 9
+4 31/3 12/9 39 1
+6 5/4 6/9 48 10
+8 10/4 2/9 58 20
+10 16/4 27/8 68 30
+12 22/4 21/8 78 40
+14 28/4 15/8 87 49
+16 4/5 9/8 97 59
+18 12/5 1/8 106 68
+20 20/5 23/7 116 78
+22 31/5 12/7 125 87
+23.26 21/6 130 92

LPPYRA12 -11 -V2.2
4ELECTRICAL CONNECTIONS
LPPYRA12, LPPYRA12AC and LPPYRA12AV have a 4-pole connector and use the
CPM12AA4... optional cables in UV resistant PTFE, with 4-pole connector on one side
and open wires on the other side.
LPPYRA12S and LPPYRA12S12 have a 8-pole connector and use the CPM12-8D...
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 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 ( ).
The wire of the cable corresponding to the housing depends on the model: white wire
in LPPYRA12 and LPPYRA12AC, black wire (cable shield) in LPPYRA12S and LPPY-
RA12S12. In LPPYRA12AV the housing is not connected directly to the connector.
4.1 LPPYRA12 CONNECTIONS
The pyranometer LPPYRA12 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 py-
ranometer output signal does not exceed 20 mV. In order to better exploit the pyra-
nometer features, the readout instrument should have 1 µV resolution.
Connector Function Color
1
Vout (+)
Red
2
Vout (-)
Blue
3
Housing
White
4
Cable shield
Black
Fig. 4.1: LPPYRA12 connections
CPM12AA4… cable
Sensor M12
male connector
Datalogger
or
converter/amplifier
withVormA output
Red [1]
Blue [2]
Black [4]
White [3]
Connect to ground only if it is not possible to
ground locally the case of the pyranometer

LPPYRA12 -12 -V2.2
4.2 LPPYRA12AC CONNECTIONS
The pyranometer LPPYRA12AC has 4…20 mA output and requires 10…30 Vdc exter-
nal 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
White
4 Cable shield Black
Fig. 4.2: LPPYRA12AC connections
4.3 LPPYRA12AV CONNECTIONS
The pyranometer LPPYRA12AV has 0…1 V, 0…5 V or 0…10 V output (depending on
the ordered output) and requires external power supply: 10…30 Vdc for 0…1 V and
0…5 V outputs, 15…30 Vdc for 0…10 V output. It is to be connected to a power sup-
ply and an instrument with voltage input as shown in fig. 4.3. The load resistance of
the instrument reading the signal must be ≥100 kΩ.
Connector Function Color
1
Output positive (+Vout)
Red
2
Output negative (-Vout)
Power supply negative (GND)
Blue
3
Power supply positive (+Vdc)
White
4
Cable shield
Black
Fig. 4.3: LPPYRA12AV connections
CPM12AA4… cable
Sensor M12
male connector
Power supply
10…30 Vdc
Red [1]
Blue [2]
Black [4]
White [3]
Connect to ground only if it is not possible to
ground locally the case of the pyranometer
Instrument with
4…20mAinput
CPM12AA4… cable
Sensor M12
male connector
Powersupply
Red [1]
Blue [2]
Black [4]
White [3]
Instrument
with
voltage input
15…30Vdc for 0…10V output
10…30 Vdc for 0…1/5V output

LPPYRA12 -13 -V2.2
4.4 LPPYRA12S CONNECTIONS
The pyranometer LPPYRA12S 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.
4.4. 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. 4.4: LPPYRA12S connections
Before connecting the pyranometer to the RS485 network, set the address and the
communication parameters, if different from the factory preset (see chapter 6).
Pyranometer
Surge
Protector
Housing
RS485
output
Power supply
Power supply
5…30 Vdc
Red
Blue
Brown
White
CPM12-8D… cable
Pyranometer M12
male connector
PLC, data logger or
RS485/USB or
RS485/RS232
converter for PC
Other sensors with
RS485 output
Termination
Termination
Shield
Connect to ground only if it is not possible
to ground locally the case of the pyranometer

LPPYRA12 -14 -V2.2
4.5 LPPYRA12S12 CONNECTIONS
The pyranometer LPPYRA12S12 has SDI-12 output and requires 7…30 Vdc external
power supply. It is to be connected to a power supply and to an acquisition system
(data logger) as shown in fig. 4.5.
Connector Function Cable color
1 Power supply negative (GND)
SDI-12 output negative
Blue
2 Power supply positive (+Vdc) Red
3
Not connected
4
Not connected
5
SDI-12 output positive
White
6
Housing
Shield (Black)
7
Not connected
8
Not connected
Fig. 4.5: LPPYRA12S12 connections
More SDI-12 sensors can be connected in parallel. The distance between a sensor and
the acquisition system (data logger) should not exceed 60 m.
Due to its low power consumption (< 200 µA), LPPYRA12S12 is particularly suitable
for battery/solar panel-powered data acquisition systems.
Before connecting the instrument to an SDI-12 network containing other sensors, set
the address by using the proper SDI-12 command (see chapter 7).
Data logger
input
Pyranometer
Surge
Protector
Housing
SDI-12
output
Power supply
Pyranometer M12
male connector
CPM12-8D… cable
Power supply
Other SDI-12
sensor
Other SDI-12
sensor
Shield
Connect to ground only if it is not possible to
ground locally the case of the pyranometer

LPPYRA12 -15 -V2.2
5MEASUREMENT IN THE MODELS WITH ANALOG OUTPUT
Below are the ways to calculate the global irradiance in the models with analog output
LPPYRA12, LPPYRA12AC and LPPYRA12AV.
5.1 LPPYRA12
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 calibra-
tion 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 LPPYRA12AC
The 4…20 mA output signal corresponds to the 0…2000 W/m2(0…4000 W/m2 – order-
ing code LPPYRA12AC4) irradiance 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) if f.s.= 2000 W/m2
Ee= 250 •(Iout - 4) if f.s.= 4000 W/m2
where:
Eeis the irradiance expressed in W/m2;
Iout is the current expressed in mA absorbed by the pyranometer.
5.3 LPPYRA12AV
The output signal (0…1 V, 0…5 V or 0…10 V depending on the version) corresponds to
the 0…2000 W/m2(0…4000 W/ m2– ordering code LPPYRA12AV4) irradiance range.
The irradiance Eeis obtained by measuring with a multimeter the output voltage Vout of
the sensor and applying the following formula:
Ee= 2000 •Vout for the version 0…1 V with f.s.= 2000 W/m2
Ee= 4000 •Vout for the version 0…1 V with f.s.= 4000 W/m2
Ee= 400 •Vout for the version 0…5 V with f.s.= 2000 W/m2
Ee= 800 •Vout for the version 0…5 V with f.s.= 4000 W/m2
Ee= 200 •Vout for the version 0…10 V with f.s.= 2000 W/m2
Ee= 400 •Vout for the version 0…10 V with f.s.= 4000 W/m2
where:
Eeis the irradiance expressed in W/m2;
Vout is the output voltage expressed in V measured by the multimeter.

LPPYRA12 -16 -V2.2
6RS485 MODBUS-RTU OUTPUT
Before connecting the pyranometer 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 pyranometer 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 pyranometer separately. If a RS485/USB con-
verter 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 pyranometer 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 pyranometer 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 pyranometer will be con-
nected.
3. Switch the pyranometer on (if the CP24 cable is used, connect both ends of the
cable).
Power supply
or
CPM12-8D… cable
Red
Blue
Brown
White
Pyranometer
connector
CP24 cable
Pyranometer
connector

LPPYRA12 -17 -V2.2
4. Wait until the pyranometer transmits the &character, then send (within 10 sec-
onds from the pyranometer power on) the @command and press Enter.
Note: if the pyranometer 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 pyranometer.
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.

LPPYRA12 -18 -V2.2
6.2 READING THE MEASURES WITH THE MODBUS-RTU PROTOCOL
In MODBUS mode, you can read the values measured by the pyranometer through
the function code 04h (Read Input Registers). The following table lists the quantities
available with the appropriate register address:
Number
Address
Quantity
Format
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 pyranometer enters RS485 MODBUS-RTU mode after 10 sec-
onds from power on. In the first 10 seconds from power on the pyranometer does not
reply to requests from the MODBUS master unit. After 10 seconds, it is possible to
send MODBUS requests to the pyranometer.

LPPYRA12 -19 -V2.2
7SDI-12 OUTPUT
The LPPYRA12S12 pyranometers are compatible with version 1.3 of SDI-12 protocol.
The protocol communication parameters are: Baud rate = 1200. Data bits = 7, Parity
= Even, Stop bits = 1.
The communication with the instrument is performed by sending a command in the
following form:
<Address><Command>!
with <Address> = address of the instrument the command is sent to
<Command> = type of operation requested to the instrument
The instrument reply is as follows:
<Address><Data><CR><LF>
with <Address> = address of the instrument which replies
<Data> = information sent by the instrument
<CR> = ASCII character Carriage Return
<LF> = ASCII character Line Feed
The sensors come with a factory address preset to 0. The address can be modified by
using the proper SDI-12 command reported in the following table.
The following table reports the SDI-12 commands available. For consistency with SDI-
12 standard documentation, the instrument address is indicated in the table with the
letter a.
SDI-12 Commands
Command Instrument reply Description
a! a<CR><LF> Verifies the presence of the
instrument.
aI! allccccccccmmmmmmvvvssssssss<CR><LF>
with:
a = address of the instrument (1 character)
ll = SDI-12 compliant version (2 characters)
cccccccc = manufacturer (8 characters)
mmmmmm = instrument model (6 characters)
vvv = firmware version (3 characters)
ssssssss = serial number (8 characters)
⇒
Example of response:
013DeltaOhmLP-PYRA0016051518
with:
0 = instrument address
13 = SDI-12 version 1.3 compliant
DeltaOhm = manufacturer’s name
LP-PYR = instrument model
A00 = firmware version A.0.0
16051518 = serial number
Requests for information
from the instrument.
aAb!
Where:
b =new
address
b<CR><LF>
Note: if the b character is not an acceptable ad-
dress, the instrument responds with a instead of b.
Modification of the instru-
ment address.

LPPYRA12 -20 -V2.2
Command Instrument reply Description
?! a<CR><LF> Request of the address of
the instrument. If more than
one sensor is connected to
the bus, a conflict occurs.
TYPE M(START MEASUREMENT)AND TYPE C(START CONCURRENT MEASUREMENT)COMMANDS
Irradiance, signal internal level and internal temperature (if available)
aM!
aC! atttn<CR><LF> with:ttt =number of seconds necessary for the in-
strument to make the measure available
(3 characters)
n =number of detected variables (1 character
for aM!, 2 characters for aC!)
Note: ttt = 000 means datum immediately available.
Request to execute the
measurement.
aD0! a+n+w…w+v…v+t…t<CR><LF>
with:
n = content of the status register
w…w = irradiance in W/m2
v…v = signal internal level in mV
t…t =internal temperature in the set unit of
measurement (default °C) if the NTC tem-
perature sensor is present, otherwise the
fixed value 25 °C
⇒
Example of response: 0+0+228.7+3.294+25.0
probe address = 0
content of the status register = 0
irradiance = 228.7 W/m2
signal internal level = 3.294 mV
internal temperature or fixed value = 25.0 °C
Note: the status register normally contains zero; a
value different from zero indicates an error condi-
tion.
Reads the measurement.
Irradiance and internal temperature (if available)
aM1!
aC1! atttn<CR><LF> with:ttt =number of seconds necessary for the in-
strument to make the measure available
(3 characters)
n =number of detected variables (1 character
for aM1!, 2 characters for aC1!)
Note: ttt = 000 means datum immediately available.
Request to execute the
measurement.
aD0! a+w…w+t…t<CR><LF>
with:
w…w = irradiance in W/m2
t…t =internal temperature in the set unit of
measurement (default °C) if the NTC tem-
perature sensor is present, otherwise the
fixed value 25 °C
⇒
Example of response: 0+228.7+25.0
probe address = 0
irradiance = 228.7 W/m2
internal temperature or fixed value = 25.0 °C
Reads the measurement.