senseca LPSD18 Sunshine Duration Sensor Instruction Manual

: August 29, 2024
: senseca

Table of Contents

senseca LPSD18 Sunshine Duration Sensor
Product Usage Instructions
Introduction
Technical specifications
Operating principle

senseca LPSD18 Sunshine Duration Sensor

Product Usage Instructions

Operating Principle
The LPSD18 Sunshine Duration sensor measures both status and sunshine duration. It utilizes an array of photodiodes arranged in a specific geometry to ensure accurate measurements in various weather conditions.

Installation
The sensor can be installed on a mast or flat base using appropriate fixing accessories. Ensure proper power supply and connections according to the electrical requirements.

Electrical Connections
Follow the guidelines provided in the manual for correct electrical connections to ensure accurate readings and safe operation.

RS485 Modbus-RTU Output
If using the RS485 Modbus-RTU output, make sure to configure the settings as needed for data communication.

FAQ

What is the purpose of the Sunshine Duration sensor?
The sensor measures both status and sunshine duration, providing valuable data for various applications such as agriculture, photovoltaic systems, and building automations.

Can the sensor be used in harsh climates?
Yes, the sensor is equipped with a heating element to prevent condensation and ice formation, making it suitable for harsh climate conditions.

What are the available output options for the LPSD18 sensor?
The LPSD18 sensor is available with RS485 Modbus-RTU, SDI-12,voltage-free contact, analog 0-1 V, and digital voltage outputs depending on the model.

Introduction

The Sunshine Duration sensor LPSD18 measures status and sunshine duration. The WMO (World Meteorological Organization) defines the sunshine duration as the time during which the direct solar radiation exceeds the level of 120 W/m2.
The radiation measurement is performed with an array of photodiodes arranged in a particular geometry which allows to obtain an accurate measurement in any weather conditions. This solution avoids the use of mechanical moving parts and ensures high reliability over time.

The instrument, besides indicating the presence of sun as required by the WMO, measures also direct radiation (SRD), therefore it can be used as a low-cost alternative to a pyrheliometer, which use is bound to a solar tracker.
LPSD18 is equipped with a heating element separately powered and galvanically isolated, which prevents the formation of condensation on the glass surface onto which the sensitive elements are placed. For harsh climates, the above- mentioned versions are available with a second heating element (option R, LPSD18.xR), which prevents the formation of ice and prevents snow from settling.

The instrument is available in three versions, which differ in the type of output:

| OUTPUT|

Heating

---|---|---

Model

| RS485

Modbus- RTU

|

SDI-12

| Voltage-free contact| Analog

0…1 V

With option R

in the code

Voltage-free contact: closed ⇒ SRD ≥ 120 W/m2, open ⇒ SRD < 120 W/m2
Analog output: 0…1 V ⇒ 0…2000 W/m2
Digital voltage output: 1V ⇒ SRD ≥ 120 W/m2, 0V ⇒ SRD < 120 W/m2

The instrument does not need any positioning adjustment during the year and it can be installed on a mast or placed on a flat base using proper fixing optional accessories.
The application fields are multiple: from the agronomy (agricultural science) to the study the growth of crops, to photovoltaic systems for verifying their performance, to building automations for automatic opening/closing of blinds, shutters and, in general, to all those areas where it is necessary to monitor the presence of sunlight.

Technical specifications

Sensitive elements	16 Silicon photodiodes
Spectral range	360…1100 nm
Direct radiation SRD measuring range	0…2000 W/m2
Accuracy of the measurement of direct radiation	Better than 90% on the

monthly total
Accuracy of the measurement of the sunshine duration sensor| Better than 90% on the monthly total
Response time| <1 ms
Threshold value| 120 W/m2
Sunshine duration resolution| 1 s
Power supply

Consumption

| 7…30 Vdc

5mA @ 12V

Heating system

Anti-condensation device consumption Antifreeze device consumption

| 12…15 Vdc

1 W @ 12 V

5 W @ 12 V ON for internal Temp. < 6 °C,

OFF for internal Temp. > 10 °C

Internal temperature Measuring range Accuracy| ****

-40…+80 °C

± 0.5 °C

· Galvanically isolated contact closed = SRD ≥ 120 W/m2 open = SRD < 120 W/m2

LPSD18.2| · RS485 MODBUS-RTU

· Analog output 0…1 V (0…2000 W/m2)

· Digital output 0…1 V

1 V = SRD ≥ 120 W/m2

0 V = SRD < 120 W/m2

LPSD18.3| · SDI-12

· Galvanically isolated contact closed = SRD ≥ 120 W/m2 open = SRD < 120 W/m2

Operating principle

The Sunshine Duration LPSD18 is based on the use of 16 sensors arranged in such a way that, in the presence of sun, at least one of the photo-detectors is exposed to sunlight directly from the sun (besides the diffusion component).
Those sensors which are not directly illuminated by the sun are used for the measurement of the diffused light that is subtracted from the measurement of the sensor which sees the sun directly to get direct radiation.
The cylindrical glass protects the sensors and the internal circuits of the instrument from the weather and at the same time provides an excellent transparency to sun-light.
In order to avoid the formation of condensation inside the instrument, in addition to the heating element, the LPSD18 is supplied with a cartridge that must be loaded with desiccant material in colloidal silica (Silica-gel).

Installation

Before installing the sunshine duration sensor, refill the cartridge containing silica-gel crystals.
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:

Unscrew the silica gel cartridge using a coin.
Remove the cartridge perforated cap.
Open the sachet containing silica gel (supplied with the sunshine duration sensor).
Fill the cartridge with the silica gel crystals.
Close the cartridge with its own cap, paying attention that the sealing O-ring be properly positioned.
Screw the cartridge to the sunshine duration sensor body using a coin.
Check that the cartridge is screwed tightly (if not, silica gel life will be reduced).

The figure below shows the operations necessary to fill the cartridge with the silica gel crystals.

The sunshine duration sensor should be installed in a place easy to be reached for the periodical cleaning of the glass and the maintenance. At the same time, it should be avoided that buildings, trees or obstructions of any kind exceed the horizontal plane on which the sunshine duration is placed. It is acceptable to choose a location where obstacles in the path of the sun from sunrise to sunset is less than 5° from the horizontal plane of the sunshine duration sensor. It should be also checked that there are no re-flective elements that may alter the measure.

The LPSD18 does not need any positioning adjustment during the year.

Adjustable supports are available to fit the sensor to the position of the sun to the lati-tude of the place of installation:

Installation on the base LPSD18.O. The base allows the inclination of the sensor up to 80° (with graduated scale) respect to the vertical. Two adjustable feet and one fixed foot allow the sensor horizontal levelling.
Installation on a vertical Ø 40 mm mast by using the LPSD18.VK support. The support allows the inclination of the sensor up to 80° (with graduated scale) respect to the vertical and the rotation of the sensor on the horizontal plane.

Before orienting the Sunshine Duration Sensor to its final position, place it vertically and adjust the base (for installation on a plane) or support (for installation on a ø 40 mm mast) feet so that the level on the upper side of the instrument is perfectly levelled.

Orient the Sunshine Duration Sensor so that the index of the graduated scale of the support matches the value (90° – Latitude) and the top (where the spirit level is placed) is directed towards the NORTH pole, if used in the northern hemisphere, or towards south, if used in the southern hemisphere.

The angle that instrument axis should make with respect to the ground is equal to the latitude of the installation site, this way the axis of the instrument will be parallel to the earth axis North-South.

Electrical connections
The Sunshine Duration Sensor has an 8-pole connector and uses the CP18… optional cables with 8-pole connector on one side and open wires on the other side.

Connector pin N°| Function| CP18… cable

wire N°/colour

---|---|---
LPSD18.1[R]
1| Power supply negative| 12/Black + 7/Violet + 6/Pink ()
2| Power supply positive| 1/Red + 2/Blue + 4/Grey-Pink ()
3| Heating ()| 3/Yellow
4| RS485 A/-| 9/White
5| RS485 B/+| 5/Red-Blue
6| Volt-free contact output| 8/Grey
7| Heating ()| 10/Brown
8| Volt-free contact output| 11/Green
LPSD18.2[R]

1

| Power supply negative

0-1 V analog output negative 0-1 V digital output negative

| ****

12/Black + 7/Violet + 6/Pink (**)

(*) The connection of the heating is not polarized; the two wires can be reversed.
(**) Wires shorted on the connector pin.

RS485 Modbus-RTU output

LP SD18.1[R] and LP SD18.2[R] are equipped with a RS485 Modbus-RTU output. The Modbus-RTU protocol is active after 5 seconds from power on.
Before connecting the sensor to the RS485 network, an address must be assigned and the communication parameters must be set, if different from the factory preset.

Setting the communication parameters

Connect the sensor to the PC by using the supplied 8-pole M12 free connector or the op-tional CP18… cable and a RS485/USB or RS485/RS232 converter. If a RS485/USB con-verter is used, it is necessary to install the related USB drivers in the PC.

Procedure:

Start with the sensor not powered.
In the PC, start a serial communication program. Set the Baud Rate to 57600 and set the communication parameters as follows (the sensor 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 sensor will be connected.
Switch the sensor on.
Wait until the sensor transmits the & character, then send (within 5 seconds from the sensor power on) the @ command and press Enter.
Note: if the sensor does not receive the @ command within 5 seconds from power on, the RS485 MODBUS mode is automatically activated. In such a case, it is nec-essary to switch off and on again the sensor.
Send the command CAL USER ON.
Note: the command CAL USER ON is disabled after 5 minutes of inactivity.
Send the serial commands given in the following table to set the RS485 Modbus parameters:
Command| Response| Description
---|---|---
CMAnnn| &|| Set address to nnn Ranging from 1 to 247

Preset on 1

CMBn| &|| Set Baud Rate

n=0 Þ 9600

n=1 Þ 19200

Preset on 1 Þ 19200

CMPn| &|| Set parity and stop bits

n=0 Þ 8N1 (no parity, 1 stop bit) n=1 Þ 8N2 (no parity, 2 stop bits) n=2 Þ 8E1 (even parity, 1 stop bit) n=3 Þ 8E2 (even parity, 2 stop bits) n=4 Þ 8O1 (odd parity, 1 stop bit) n=5 Þ 8O2 (odd parity, 2 stop bits)

Preset on 2 Þ 8E1

CMWn| &|| Set waiting time after transmission

n=0 Þ Immediate reception (violates protocol) n=1 Þ Waiting 3.5 characters (respects protocol)

Preset on 1 Þ Waiting 3.5 characters

You can check the parameters setting by sending the following serial commands:

Command	Response	Description
RMA	Address	Read address
RMB	Baud Rate

(0,1)

| Read Baud Rate

0 ⇒ 9600

1 ⇒ 19200

RMP| Tx Mode

(0,1,2,3,4,5)

| Read parity and stop bits

0 ⇒ 8N1

1 ⇒ 8N2

2 ⇒ 8E1

3 ⇒ 8E2

4 ⇒ 8O1

5 ⇒ 8O2

RMW| Rx Mode

(0,1)

| Read waiting time after transmission

0 ⇒ Immediate reception (violates protocol)

1 ⇒ Waiting 3.5 characters (respects protocol)

Note: it is not required to send the CAL USER ON command to read the settings.

Reading the measures with the Modbus-RTU protocol Below is the list of registers.

Input Registers

Address	Quantity	Format
0	Internal temperature °C [x10]	16-bit integer
1	Internal temperature °F [x10]	16-bit integer
2	Direct radiation (SRD, “Direct Sunshine”) in W/m2	16-bit integer
3	Status register

Bit0=1 ⇒ error in the measure of radiation Bit1=1 ⇒ error in the measure of temperature Bit2=1 ⇒ data memory error

Bit3=1⇒ program memory error

| 16-bit integer
4| Number of seconds in the last minute with radiation higher than 120 W/m2 (number between 0 and 60)| 16-bit integer
5| Number of tens of seconds in the last 10 minutes with radia- tion ³ 120 W/m2 (number between 0 and 60: for each interval of 10 s, in the last 10 minutes, is counted a 1 if SRD ³ 120 W/m2 for at least 5 s)

For a higher resolution use the register number 5.

| 16-bit integer
6| Status of the sun presence/absence contact 0 = SRD < 120 W/m2 (open contact)

1 = SRD ³ 120 W/m2 (closed contact)

For the numbering of the sensors see the following figure. To identify the sensors, the reference is the square mark at the top when the sensor is installed.

Change of the heating activation temperature
The temperature below which the heating turns on can be changed by writing the value in the Holding Register with address 2. The value must be set in tenths of degrees between -450 (-45.0 °C) and 700 (+70.0 °C).
The modification of the Holding Register with address 2 changes only the value in the RAM memory, the change is therefore cancelled in case of instrument power supply failure. To make the change permanent, write the hexadecimal value FF00 in the Coil Register with address 2.

To check if the permanent storage has been completed successfully, verify that the Holding Register with address 1 contains the value 0.

Coils

Address	Datum
2	Permanent storage of the heating activation temperature.

Holding Registers

Address	Datum	Format
0	Indicator of the correct interpretation of the last Modbus command sent.

If 0, the command has been executed correctly. If 1, command execution errors occurred.

| 16-bit integer
1| Indicator of the correct permanent storage of heating activa- tion temperature.

If 0, the temperature has been stored correctly. If 1, storage errors occurred.

| 16-bit integer
2| Heating activation temperature in °C [x10].| 16-bit integer

CHECK OF THE CORRECT INTERPRETATION OF THE MODBUS COMMANDS: in order to check if the last Modbus command sent to the instrument has been interpreted correctly, veri-fy that the Holding Register with address 0 contains the value 0.

SDI-12 output

LPSD18.3 is equipped with an SDI-12 communication interface compliant with the version 1.3 of the 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>!
with

= address of the instrument the command is sent to = type of operation requested to the instrument

The instrument reply is as follows:

< Address>
with

= address of the instrument which replies

= information sent by the instrument = ASCII character Carriage Return = 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	Verifies the presence of the instrument.
aI!	allccccccccmmmmmmvvvssssssss 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)

Þ Example of response: 013DeltaOhmLPSD1810013201518

with:

0 = instrument address

13 = SDI-12 version 1.3 compliant DeltaOhm = manufacturer’s name LPSD18 = instrument model

100 = firmware version A.0.0 13201518 = serial number

| Requests for information from the instrument.
aAb!

Where:

b =new

address

| b

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.
---|---|---
?!| a| Request of the address of the instrument. If more than one sensor is connected to the bus, a conflict occurs.
T YPE M ( START MEASUREMENT ) AND TYPE C ( START CONCURRENT MEASUREMENT ) COMMANDS
Insolation status
aM!

aC!

| atttn

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 of detection of the insolation status (presence or absence of sun).
aD0!| a+x

with: x = 0 if SRD < 120 W/m2, x = 1 if SRD ≥ 120

W/m2

Þ Example of response: 0+0

The instrument with address 0 measures SRD < 120 W/m2

| Reads the status of insola- tion (presence or absence of sun).
Direct Solar Radiation
aM1! aC1!| atttn

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 for performing the measurement of direct so- lar radiation (SRD) in W/m2.
aD0!| a+rrrr

with: rrrr = SRD with resolution 1 W/m2

Þ Example of response: 0+0135

The instrument with address 0 measures SRD = 135 W/m2

| Reads the measurement of direct solar radiation (SRD) in W/m2.
State and duration of sunshine

aM2! aC2!| atttn

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 aM2!, 2 characters for aC2!)

Note: ttt = 000 means datum immediately available.

| Request for detecting sta- tus and lasting of insola- tion.
aD0!| a+x+mm+dd+nnnnn with:

x = 0 if SRD < 120 W/m2, x = 1 if SRD ≥ 120

W/m2

mm = number of seconds in the last minute with x=1

dd = number of tens of seconds in the last 10 minutes with x=1 (dd=0…60: for each interval of 10 s, a 1 is added if x=1 for at least 5 s)

nnnnn =circular counter of the measuring cycles number.

Þ Example of response: 0+1+25+12+00048

The instrument with address 0 measures x=1, in the last minute there have been 25 s with x=1, in the last 10 min there have been from 60 to 120 s with x=1, 48 measuring cycles have elapsed since the counter reset.

| Reads status and lasting of isolation.
Internal temperature and heating status
aM3! aC3!| atttn

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 aM3!, 2 characters for aC3!)

Note: ttt = 000 means datum immediately available.

| Request of detecting the internal temperature and the heating status.
aD0!| a+nn.d+n

with:nn.d = internal temperature in °C

n = 0 when heating OFF, n = 1 when heating ON

Þ Example of response: 0+15.3+0

the instrument with address 0 measures 15.3 °C of internal heating and the heater is switched off.

| Reads the internal tempera- ture and the heating status.
T YPE R ( CONTINUOUS MEASUREMENTS ) COMMANDS
aR0!| a+x

with: x = 0 if SRD < 120 W/m2, x = 1 if SRD ≥ 120

W/m2

| Reads the status of insola- tion (presence of absence of sun).
aR1!| a+rrrr

with: rrrr = SRD with resolution 1 W/m2

| Reads the measure of the

direct solar radiation (SRD) in W/m2

aR2!| a+x+mm+dd+nnnnn with:

x = 0 if SRD < 120 W/m2, x = 1 if SRD ≥ 120

W/m2

mm = number of seconds in the last minute with x=1

dd = number of tens of seconds in the last 10 minutes with x=1 (dd=0…60: for each interval of 10 s, a 1 is added if x=1 for at least 5 s)

nnnnn =circular counter of the measuring cycles number

| Reads status and lasting of insolation.
---|---|---
aR3!| a+nn.d+n

with:nn.d = internal temperature in °C

n = 0 when heating OFF, n = 1 when heating

ON

| Reads internal tempera- ture and status of heating

In addition to the above-mentioned commands, the sensor also implements the corre-sponding commands with CRC, that require to add a 3-character CRC code at the end of the reply before . The format of these commands is obtained from the pre-vious by adding the letter C: aMC!, aMC1!, aMC2!, aMC3!, aCC!, aCC1!, aCC2!, aCC3!.

For more information about the SDI-12 protocol, visit the website “www.sdi-12.org“.

Maintenance

In order to grant measurements high accuracy, it is important to keep the protective glass clean.
You can wash it using water and microfiber cloths for lens. If necessary, use pure ETHYL alcohol. After using alcohol, clean again the protective glass with water only and dry it thoroughly.

In order to minimize the condensation, the sensor is provided with a heating element and a cartridge containing dessicant material (silica-gel). The efficiency of the silica-gel crystals decreases over time while absorbing humidity. Silica-gel crystals are effi-cient when their color is yellow, while they turn white/translucent as soon as they lose their efficiency. Read instructions on chapter Errore. L’origine riferimento non è stata trovata. about how to replace the silica-gel crystals. Silica-gel typical lifetime goes from 2 to 6 months depending on the environment where the sensors works.

Safety instructions

The instrument proper operation and operating safety can be ensured only in the cli-matic conditions specified in this manual and if all standard safety measures as well as the specific measures described in this manual are followed.

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:

EU directives on workplace safety.
National law regulations on workplace safety.
Accident prevention regulations.

Accessories ordering codes

CP18… Cable with 8-pole M12 connector on one end, open wires on the other end. Length 5 m (CP18.5) or 10 m (CP18.10).
LPSD18.O Base for installation of the sunshine duration sensor on a horizontal plane. Two adjustable feet and one fixed foot. Allows the inclination of the sensor up to 80° (with graduated scale) from the vertical, to suit the position of the sun to the latitude of the place of installation.
LPSD18.VK Support for installation of the sunshine duration sensor on a mast Ø 40 mm. Allows the inclination of the sensor up to 80° (with graduated scale) from the vertical, to suit the position of the sun to the latitude of the place of installation. It allows the rotation of the sensor on a horizontal plane.
LPSG Cartridge for containing crystals of silica gel with O-ring.
LPG Pack of 5 cartridges of the silica-gel.

WARRANTY

The manufacturer is required to respond to the “factory warranty” only in those cases provided by Legislative Decree 6 September 2005 – n. 206. Each instrument is sold after rigorous inspections; if any manufacturing defect is found, it is necessary to contact the distributor where the instrument was purchased from. During the warranty period (24 months from the date of invoice) any manufacturing defects found will be repaired free of charge. Misuse, wear, neglect, lack or inefficient maintenance as well as theft and damage during transport are excluded. Warranty doesnot apply if changes, tampering or unauthorized repairs are made on the product. Solutions, probes, electrodes and microphones are not guaranteed as the improper use, even for a few minutes, may cause irreparable damages.

The manufacturer repairs the products that show defects of construction in accordance with the terms and conditions of warranty included in the manual of the product. For any dispute, the competent court is the Court of Padua. The Italian law and the “Convention on Contracts for the International Sales of Goods” apply.

TECHNICAL INFORMATION
The quality level of our instruments is the result of the continuous product development. This may lead to differences between the information reported in the manual and the instrument you have purchased.
We reserve the right to change technical specifications and dimensions to fit the product requirements without prior notice.

DISPOSAL INFORMATION
Electrical and electronic equipment marked with specific symbol in compliance with 2012/19/EU Directive must be disposed of separately from household waste.
European users can hand them over to the dealer or to the manufacturer when purchasing a new electrical and electronic equipment, or to a WEEE collection point designated by local authorities. Illegal disposal is punished by law.
Disposing of electrical and electronic equipment separately from normal waste helps to preserve natural resources and allows materials to be recycled in an environmentally friendly way without risks to human health.

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Via Marconi, 5
35030 Selvazzano Dentro (PD)
ITALY
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