EKO MS-40S User manual

INSTRUCTION MANUAL
MS-40
MS-40S
Pyranometer
ISO9060:2018 Class C
ISO9060:1990 Second Class

EKO INSTRUMENTS CO., LTD. - Pyranometer MS-40/40S - Instruction Manual Ver. 4
Pg. 2
1. Index
1. Index 2
2. Important User Information 3
2-1. Contac t I nformation 3
2-2. Warr ant y a n d Lia b ility 3
2-3. About O perati n g Manua l 4
2-4. E n v iron m e n t 4
2-5. I SO/IEC 17 0 25 5
2-6. C E Declar ation 6
3. Safety Information 7
3-1. G e n eral War nings 7
4. Introduction 9
4-1. I ntroduc tio n 9
4-2. P ackage C ontents 10
5. Getting Started 11
5-1. P ar ts Descript i o n s 11
5-2. S e tup 13
5-3. M e asuring S olar I rradi a nce 19
6. Maintenance & Troubleshooting 21
6-1. M a intenance 21
6-2. C alibr at i on and M easur em ent Uncer t a i nty 23
6-3. Troub leshoot ing 24
7. Specification 25
7-1. S p ec ific ations 25
7-2. D im ensio ns 27
7-3. O u tput Ca b l es 28
7-4. Accessori es List 28
APPENDIX 29
A-1. Radiom etr ic Term s 29
A-2. P yranom eter Characteris t ics 30
A-3. Configurator Softwar e [ M S -4 0 S] 31
A-4. Communicat ion S pec if ic a t ions [ MS-40S Mo d bus RTU] 35
A-5. C omm unic a t ion S pecif ic a t ions [ M S -40S SDI-12] 43
A-6. Recali br ation 44

EKO INSTRUMENTS CO., LTD. - Pyranometer MS-40/40S - Instruction Manual Ver. 4
Pg. 3
2. Important User Information
Thank you for using EKO Products.
Reading this manual is recommended prior to installation and operation of the product. Keep this
manual in safe and handy place for whenever it is needed.
For any questions, please contact us at below:
2-1. Contact I nformati on
EKO INSTRUMENTS CO., LTD.
Asia, Oceania Region
https://eko-asia.com
[email protected]
EKO INSTRUMENTS Co., Ltd.
1-21-8 Hatagaya, Shibuya-ku
Tokyo, 151-0072 Japan
Tel: +81 [3] 3469-6713
Fax: +81 [3] 3469-6719
Europe, Middle East, Africa, South America Region
https://eko-eu.com
[e-mail]
EKO INSTRUMENTS Europe B.V.
Lulofsstraat 55, Unit 28,
2521 AL, Den Haag, The Netherlands
Tel: +31 [0]70 3050117
Fax: +31 [0]70 3840607
North America Region
https://eko-usa.com
[e-mail]
EKO INSTRUMENTS USA Inc.
111 North Market Street, Suite 300
San Jose, CA 95113 USA
Tel: [phone]
Fax: [phone]
2-2. Warrant y an d Liability
For warranty terms and conditions, please contact EKO Instruments or your distributer for further details.
EKO guarantees that the product delivered to customer has been tested to ensure the instrument meets its
published specifications. The warranty included in the conditions of delivery is valid only if the product has
been installed and used according to the instructions provided in this operating manual.
In case any manufacturing defect[s] will occur, the defected part[s] will be repaired or replaced under
warranty; however the warranty will not be applicable if:
➢Any modification or repair has been done by other than EKO service personnel.
➢The damage or defect is caused by disrespecting the specifications mentioned on the product
brochure or instruction manual.

EKO INSTRUMENTS CO., LTD. - Pyranometer MS-40/40S - Instruction Manual Ver. 4
Pg. 4
2-3. About Op erati ng Manual
Copy Rights Reserved by EKO INSTRUMENTS CO., LTD. Making copies of whole or part of this document
without permission from EKO is prohibited.
This manual was issued: 2019/7/30
Version Number: 4
2-4. Environment
1. WEEE Directive 2002/96/EC
[Waste Electrical and Electronic Equipment]
In August of 2005, the European Union [EU] implemented the EU WEEE Directive 2002/96/EC and later the
WEEE Recast Directive 2012/19/EU requiring Producers of electronic and electrical equipment [EEE] to
manage and finance the collection, reuse, recycling and to appropriately treat WEEE that the Producer places
on the EU market after August 13, 2005. The goal of this directive is to minimize the volume of electrical and
electronic waste disposal and to encourage re-use and recycling at the end of life.
EKO products are subject to the WEEE Directive 2002/96/EC. EKO Instruments has labeled its branded
electronic products with the WEEE Symbol [figure Trash bin] to alert our customers that products bearing this
label should not be disposed of in a landfill or with municipal or household waste in the EU.
If you have purchased EKO Instruments branded electrical or electronic products in the EU and are intending
to discard these products at the end of their useful life, please do not dispose of them with your other
household or municipal waste. Disposing of this product correctly will help save valuable resources and
prevent any potential negative effects on human health and the environment, which could otherwise arise
from inappropriate waste handling.
2. RoHS Directive 2002/95/EC
EKO Instruments has completed a comprehensive evaluation of its product range to ensure compliance with
RoHS Directive 2002/95/EC regarding maximum concentration values for substances. As a result all products
are manufactured using raw materials that do not contain any of the restricted substances referred to in the
RoHS Directive 2002/95/EC at concentration levels in excess of those permitted under the RoHS Directive
2002/95/EC, or up to levels allowed in excess of these concentrations by the Annex to the RoHS Directive
2002/95/EC.

EKO INSTRUMENTS CO., LTD. - Pyranometer MS-40/40S - Instruction Manual Ver. 4
Pg. 5
2-5. ISO/IEC 17 025
EKO Instruments Co. Ltd. calibration laboratory is accredited by Perry Johnson Laboratory Accreditation, Inc.
[PJLA] to perform pyranometer and pyrheliometer calibrations in accordance with the requirements of
ISO/IEC17025, which are relevant to calibration and testing.
EKO is a unique manufacturer who can offer calibration service for pyranometers and pyrheliometers
in-house. Based on the applied calibration methods EKO provides the best quality solar sensor calibrations
compliant to the international standards defined by ISO/IEC17025 / 9847 [Indoor method] and ISO9059
[Outdoor method] [Certification: L13-94-R2 / www.pjlabs.com]
ISO/IEC17025 provides a globally accepted basis for laboratory accreditation that specifies the management
and technical requirements. With calibrations performed at the EKO Instruments laboratory we enable our
customers to:
・ Clearly identify the applied calibration methods and precision
・ Be traceable to the World Radiation Reference [WRR] through defined industrial standards:
ISO9846 Calibration of a pyranometer using a pyrheliometer
ISO9847 Calibration of field pyranometer by comparison to a reference pyranometer
ISO9059 Calibration of field pyrheliometers by comparison to a reference pyrheliometer
・ Obtain repeatable and reliable calibration test results through consistent operations
Our clients will obtain a highly reliable data by using an ISO/IEC17025 calibrated sensor. Our accredited lab is
regularly re-examined to ensure that they maintain their standards of technical expertise.

EKO INSTRUMENTS CO., LTD. - Pyranometer MS-40/40S - Instruction Manual Ver. 4
Pg. 6
DECLARATION OF CONFORMITY
We: EKO INSTRUMENTS CO., LTD
1-21-8 Hatagaya Shibuya-ku,
Tokyo 151-0072 JAPAN
Declare under our sole responsibility that the product:
Product Name : Pyranometer
Model No. : MS-40, MS-40S
To which this declaration relates is in conformity with the following
harmonized standards of other normative documents:
Harmonized standards:
EN 61326-1:2006 Class A [Emission]
EN 61326-1:2006 Class A [Immunity]
Following the provisions of the directive:
EMC-directive: 89/336/EEC
Amendment to the above directive: 93/68/EEC
Date: April 4 , 2019
Position of Authorized Signatory: General Manager of R & D Department
Name of Authorized Signatory: Shuji Yoshida
Signature of Authorized Signatory:
2-6. CE Declaration

EKO INSTRUMENTS CO., LTD. - Pyranometer MS-40/40S - Instruction Manual Ver. 4
Pg. 7
3. Safety Information
EKO Products are designed and manufactured with consideration for safety; however, please make
sure to read and understand this instruction manual thoroughly to be able to operate the instrument
safely in the correct manner.
WARNING
CAUTION
Attention to user; pay attention to the instructions given on the
instruction manual with this sign.
HIGH
VOLTAGE
WARNING
High voltage is used; pay special attention to instructions given in
this instruction manual with this sign to prevent electric leakage
and/or electric shocks.
3-1. Ge neral Warnings
1. Setup
➢The installation base or mast should have enough load capacity for the instrument to be mounted.
Fix the pyranometer securely to the base or mast with bolts and nuts; otherwise, the instrument
may drop due to gale or earthquake, which may lead to unexpected accidents.
➢Make sure the instrument and the cables are installed in a location where they will not get soaked.
➢When using this instrument by connecting to a measuring instrument, make sure to connect the
shield cable to either the signal ground terminal on the measuring instrument side or GND [the
reference potential on the single end input side]. Noise may be included in the measurement data.
➢Although this product is tested to meet EMC Directive compliance requirements, it may not fully
satisfy its primary specification/performance when using this product near following locations
where strong electromagnetic wave is generated. Please pay attention to the installation
environment.
Outdoor: High voltage power line, power receiver/distribution facility, etc.
Indoor: Large-size chiller, large rotation device, microwave, etc.
➢Do not use this product in environment where corrosive gas, such as ammonia and sulfurous acid
gas, are generated. It may cause malfunction.
➢Do not install in area that cause salt damages. It may cause malfunction by paint peeling off or
corrosion. When installing in area with risk of salt damages, make sure to take following
measures:
1. Wrap the connector with self-fusing tape.
2. Change the fixing screw to bolt screw made of aluminum.
3. Run the cables in resin pipe or metal pipe treated with salt-resistant paint such as molten zinc
plating.
4. Periodically clean.

EKO INSTRUMENTS CO., LTD. - Pyranometer MS-40/40S - Instruction Manual Ver. 4
Pg. 8
➢Do not use this instrument in vacuum environment.
➢If the cable and main unit are in risk for getting damaged by birds and small animals, protect the
cable and the main unit by using:
1. Reflective tape
2. Repellent
3. Cable duct
4. Installing bird-spike
2. Handing
➢Be careful with glass dome when handling instruments. Strong impact to this part may damage the
glass and may cause injuries by broken glass parts.
➢When carrying the MS-40 with sunscreen attached, always hold the instrument from the bottom.
Holding only the sunscreen part may lead to dropping the sensor as it comes off from the
sunscreen.
➢When using the 0 to1V, please prepare the precision resister 100Ω. If 0-1V output is not selected as
a purchase option, 0-1V output is off. Or the setting can be changed with the 485 / USB conversion
cable and dedicated software.
3. Power Supply [MS-40S]
➢Make sure to ground the power supply. When grounding is insufficient, it may cause not only
measurement error due to noise, but also cause electric shock and leakage accidents.
➢Check the voltage and types of specified power supply before connecting this instrument. When
improper power supply is connected, it may cause malfunction and/or accident.
➢Use this instrument with 0.5A fuse connected to the power supply line in series. Without connecting
the fuse, it has risks of generating heat and fire due to large-current flowing by the power supply
when internal damage on the electronics will occurs.

EKO INSTRUMENTS CO., LTD. - Pyranometer MS-40/40S - Instruction Manual Ver. 4
Pg. 9
4. Introduction
4-1. Introduction
The MS-40 sensor is perfectly suited measuring the solar energy in horizontal or tilted measurement
configurations. It is fully compliant with the “Spectrally flat Pyranometer of Class C” of ISO9060: 2018
standard. The MS-40 Pyranometer is sensitive within the entire spectral range from 285 to 3000nm. It can be
applied within the most demanding applications for solar radiation measurements.
The S-model has smart electronics, which provided advanced measurement functions with different industrial
signal outputs (MODBUS 485 RTU, SDI-12, 4-20mA, configurable 0-10mA / 0-1V with optional precision
shunt resistor 100Ω) and on-board sensors for remote diagnostics of the sensor temperature, relative
humidity and tilt position.
The MS-40 can be used in combination with the optional MV-01 [ventilator + heater unit] to reduce dew,
condensation and accumulation of dusts and snow on glass dome. The ventilation unit with heater is
recommended when the sensor will be deployed in harsh climate regions.
Each MS-40 is calibrated and tested at EKO upon manufacture against EKO’s reference sensors, which are
fully traceable to the WRR [World Radiometric Reference] maintained at the PMOD/WRC
[Physikalisch-Meteorologisches Observatorium Davos/World Radiation Center] in Davos, Switzerland.
Besides, EKO provides a unique calibration service for pyranometers and pyrheliometers compliant to the
international standards defined by ISO/IEC17025/9847/9059 [Outdoor calibration method]. When an ISO/
IEC17025 calibrated sensor is purchased, EKO offers sensor at nearly constant calibration uncertainty. The
Accredited lab is regularly re-examined to ensure that they maintain their standards of technical expertise.
ISO 9060, an international industry standard, was revised to the 2nd edition in 2018. Along with this revision,
the Pyranometers are classified in order of the highest grade "Class A" "Class B" "Class C" and for
Pyranometers that meet the response time and spectral selectivity criteria, "fast response pyranometer" and
"spectrally flat radiometer" are classified as a sub-category.
1. MS-40
The analog MS-40 can be used in traditional sensor networks in combination with a data logger with
high-resolution mV input channels. The sensor has a light-weight anodized aluminum housing and
precision-machined hemispherical glass dome to provide good performance characteristics. The MS-40 is a
perfect balance between cost-effectiveness and quality.
2. MS-40S
The MS-40S with smart sensor technology and onboard diagnostic functions. 4 different output types can be
selected, which is a great benefit for system integrators who work with various industrial standards. This new
Smart transducer will also have additional features such as internal temperature and humidity sensors and a tilt
sensor for remote sensor diagnostics. These additional internal sensors will help the user to monitor the
stability of the irradiance sensors as well as to ensure its proper installation and maintenance practices.
Up to 100 smart sensors can be connected in one network. The signal converter settings can be changed
using the optional RS485 / USB converter cable and the configurator software.

EKO INSTRUMENTS CO., LTD. - Pyranometer MS-40/40S - Instruction Manual Ver. 4
Pg. 10
Category of ISO9060: 2018
“spectrally flat pyranometer of class C”
Key features:
•Outputs (MODBUS 485 RTU, SDI-12, 4-20mA, configurable 0-10mA / 0-1V with external optional 100Ω
precision shunt resistor)
•Wide range of voltage supplies available [DC 5 to 36 V]
•With built-in tilt / role sensor to check the sensor position over time.
•Humidity and temperature sensor to monitor the sensor temperature and condition of the drying agents
(silica gel) inside the sensor body.
4-2. Package Co ntents
Check the package contents first; if any missing item or damage is noticed, please contact EKO immediately.
Table 4-1. Package Contents
Contents
MS-40 / 40S
Pyranometer
○
Output Cable *
○
Sunscreen
○
Calibration Certificate
○
Quick Start Guide
○
Instruction Manual
Not included in the package
[Please download from EKO Website]
Inspection Report
-
Fixing Bolts
[ M5 ] x2
[Bolt Length: 75mm ]
Washers
[ M5 ] x4
Nuts
[ M5 ] x2
* Standard length is 10m for signal cable. For different length of cables [e.g. to meet your application needs]
please contact EKO or your local distributor.

EKO INSTRUMENTS CO., LTD. - Pyranometer MS-40/40S - Instruction Manual Ver. 4
Pg. 11
5. Getting Started
5-1. Parts D escriptions
Each part name and its main function is described below.
Parts Name
A. Glass Dome
B. Detector
C. Body
D. Leveling Screw
E. Cable, Connector
F. Spirit level
G. Silica-gel
H. Sunscreen
Figure 5-1. Pyranometer Parts Name
1. Glass Dome
A glass dome creates a sealed environment for the detector and protects it against the dirt, rain and wind.
Besides the mechanical protection, the optical properties of the glass dome minimize the undesired influence
of long wave radiation on the shortwave radiation: the dome of the EKO pyranometers is only transparent for
radiation emitted by the sun. Hence they block the undesired infrared radiation emitted by the Earth’s
atmosphere. The glass dome of all EKO thermopile pyranometers permit to measure the cosine-weighted
global solar irradiance over the entire hemisphere, i.e. with a field-of-view of 180 degree.
2. Detector
Thermopile detector, which generates a voltage proportional to temperature difference [Seebeck Effect.
When light is irradiated on the sensor, temperature of the detector increases; creating the temperature
difference at cold junction [body part] will generate electromotive force on the thermopile. The pyranometer
will output this electromotive force as voltage, and by measuring this voltage to determine the solar irradiance.
The thermopile detector, which is the heart of the sensor, determines the majority of the measurement
properties [e.g. response time, zero offset B, non-linearity, sensitivity, etc.]. EKO thermopile detectors are very
stable in time due to the black absorber material, which has high absorption and no wavelength dependency
is used on the detector surface.
E
F
A
B
C
G
H
D
Table 5-1. Parts Name

EKO INSTRUMENTS CO., LTD. - Pyranometer MS-40/40S - Instruction Manual Ver. 4
Pg. 12
3. Sunscreen, Body and Spirit Level
The sunscreen prevents excessive body temperature increase generated by direct sun-light. Weather
resistant metal is used for the body, which has resistant against decrease of night-time radiation and heat
radiation, and rain and dusts. The integrated sprit level is used to setup and maintain the sensor in a
horizontally leveled position.
4. Drying agent
Enclosed drying agents inside the sensor body keep the sensor inside dry, prevents condensation of humidity
inside of the glass dome. There is no need to replace the drying agents as they are replaced when sensor is
recalibrated at EKO.
5. Cable and Cable Connector
All pyranometers are shipped with a 10 meter long output cable as standard length*.
Durable materials are used for the cable and connector, and pin terminals are attached at the end of the cable
for easy connection with data logger terminal block.
* If longer cables, round terminals or fork terminals are required, please contact EKO Instruments or your
distributor. [Also see [7. Specification, 7-4. Accessories List] for optional items.]
The connector should be protected by the self-fusing tape when the pyranometers are used in the areas
with the risk of the salt damage.

EKO INSTRUMENTS CO., LTD. - Pyranometer MS-40/40S - Instruction Manual Ver. 4
Pg. 13
5-2. Setu p
In order to obtain representative measurements from pyranometers, several criteria with respect to setup and
mounting of the instruments have to be considered.
The ideal mounting position for pyranometers is a location which has a full hemispheric field-of-view without
any obstructions [such as buildings, trees, and mountain]; however, it might be difficult to find such locations.
Therefore in practice, it is ideal to install in a position which is free from obstructions at 5° above horizon.
The setup location should be easily accessible for periodic maintenance [glass dome cleaning, etc.], and
avoid surrounding towers, poles, walls or billboards with bright colors that can reflect solar radiation onto the
pyranometer. A strong physical impact to the pyranometer can lead to product damage and/or may cause
changes to the sensitivity.
1. Installing at Horizontal or Tilted Positions
1) Check the installation base where the pyranometer has to be mounted and make sure it has two fixing
holes with the appropriate pitch. The pitch sizes of the fixing holes are as follows [in mm]:
Table 5-2. Fixing Hole Pitch and Bolt Size for Pyranometers
MS-40 / MS-40S
Fixing Hole Pitch
65 mm
Fixing Bolt Size
M5 x 75 mm
2) Setup the pyranometer with the signal cable connector facing the nearest Earth’s pole.
In the Northern hemisphere, the connector should be orientated North, in the Southern hemisphere, the
connector should be orientated South. If the signal cable connector is facing towards the sun, the
temperature of the connector increases and may cause measurement error due unwanted
thermoelectric power induced by the connector temperature increase.
3) Remove the sun-screen.
The Sunscreen can be removed by loosening the knurling screw and sliding it towards the spirit level
direction.
*When carrying the MS-40 with sunscreen attached, always hold the instrument from the bottom.
Holding only the sunscreen part may lead to dropping the sensor as it comes off from the sunscreen.
4) Adjust the pyranometer in a horizontal position by using the 2 levelling screws observing the air bubble in
the spirit level while manipulating the levelling screws. The instrument is levelled horizontally if the air
bubble is in the centre ring.
If the pyranometer is not levelled properly, the pyranometer readings are affected by cosine and azimuth
errors. Periodically check the spirit level and adjust the pyranometer’s position if necessary.

EKO INSTRUMENTS CO., LTD. - Pyranometer MS-40/40S - Instruction Manual Ver. 4
Pg. 14
[Installing at Tilted Position]
After the MS-40 is adjusted to horizontal position in levelled surface, install it on tilted mounting position.
*When installing the instrument, do not remove the levelling feet or fixed feet; if the levelling feet are
removed, it may cause abnormal output values due to the thermal effects from the mounting part.
In the case of MS-40S, it is possible to acquire tilt information obtained from the built-in tilt sensor
through Modbus RTU.
5) Fasten the pyranometer to the base with the 2 bolts [included] and put the sunscreen back on the
pyranometer.
2. Wiring
To extend the cable lifetime, make sure that the cables are not exposed to direct sun light or rain/wind by lining
the cable through a cable conduit. Cable vibrations will potentially cause noise in the output signal. Fasten the
cable so that the cable does not swing or move by wind blowing.
Exposure of the signal cable to excessive electromagnetic emissions can cause noise in the output signal as
well. Therefore the cable should be lined at a safe distance from a potential source generating EMC noise,
such as an AC power supply, high voltage lines or telecom antenna.
◼Wiring Procedure
1) Connect the output cable to the pyranometer by inserting the cable connector to the connector on the
body then turn the screw cap.
*Make sure to check the pin layout of the connector before connecting the cable. If the connector cannot
be easily inserted, DO NOT use any force as it will damage the connector. Visually check the pin layout
again before retrying to insert the connector. *Make sure to fasten the screw cap by turning it all the way.
2) Connect the output cable:
2-1. How to Connect MS-40 [See Table 5-3. Wire Color Codes also]
Connect the wires with colors that correspond to each terminal to voltmeter or data logger.
*To prevent noise always connect the shield cable.
Figure 5-2. How to connect MS-40
+
Measuring
Device
-
SG

EKO INSTRUMENTS CO., LTD. - Pyranometer MS-40/40S - Instruction Manual Ver. 4
Pg. 15
2-2. How to Connect MS-40S [See Table 5-4 Wire Color Codes also]
A] How to connect 4-20mA
Connect the output cable, DC power supply [5 to 36 V], and ammeter as shown in the figure
below. Install a fuse [0.5A] in series between the DC power supply [+] and the MS-40S
connection as shown below for over current protection.
* When precision resistors are connected in parallel and acquired at voltage value, keep the
precision shunt resistor maximum value at 150Ω.
Connection for measuring by Current
Figure 5-3A. How to connect 4-20mA output
B] How to connect 0-1V[optional]
The default output is 4-20mA. If 0 to 1V output is not selected as a purchase option, 0 to 1V
output is off. Or the setting can be changed with the 485 / USB conversion cable and dedicated
software.
Connect the output cable, DC power supply [5 to 36 V], precision resistor 100Ω[* please
prepare separately], and voltage measurement device as shown in the figure below. Install a
fuse [0.5A] in series between the DC power supply [+] and the MS-40S connection as shown
below for over current protection.
Connection for measuring by voltage
[Connecting precision resistance in series]
Figure 5-3B. How to connect 4-20mA output
-
+
4-20mA Input
Measurement Device
fuse[0.5A]
Power supply
DC5V to 36V
-
+
0 to 1V Input
Measurement device
+
-
fuse [0.5A]
R
-
Power supply
DC5V to 36V
+
-

EKO INSTRUMENTS CO., LTD. - Pyranometer MS-40/40S - Instruction Manual Ver. 4
Pg. 16
[C] How to connect Modbus RTU
Connect the output cable and DC power [5 to 36 V], RS485 to USB converter or data logging
device as shown in the figure below. Install a fuse [0.5A] in series between the DC power supply
[+] and the MS-40S connection as shown below for over current protection.
[D] How to connect SDI-12
Connect the output cable, DC power supply [12 V], and data logging device as shown in the
figure below. Install a fuse [0.5A] in series between the DC power supply [+] and the MS-40S
connection as shown below for over current protection.
Figure 5-3E. How to connect MS-40S
Power supply
DC12V
Data collection device
SDI-12
+
-
+
-
fuse [0.5A]
When connecting to a PC
When connecting to a Data Logger
Fig. 5-3D. How to connect MS-40S
Power supply
DC5V to 36V
+
-
Data collection device
RS-485 Modbus
-
fuse[0.5A]
+
Fig. 5-3C. How to connect MS-40S
Power supply
DC5V to 36V
+
-
RS485/USB
Converter
+
-
fuse[0.5A]
PC

EKO INSTRUMENTS CO., LTD. - Pyranometer MS-40/40S - Instruction Manual Ver. 4
Pg. 17
2-3. How to Connect Communication with Modbus RTU
MS-40S can connect to a system that communicates with Modbus RTU by using RS-485.
Maximum of 100 units can be connected, and individual address can be assigned.
Connection of MS-40S to the RS-485 communication network is shown below.
Master represents the data logging device [such as PC], and slaves represent devices such as
MS-40S.
Connect the + and – for the master to [A] and [B] for each MS-40S. Also at the end of network,
connect a 120Ω termination resistor.
Modbus address is the last 2 digits of the product serial number. If the last 2 digits are “00”, the
address will be “100”.
[*]Communication errors may occur depending on the connection distance and the number of
connections. In that case, please use RS485 booster or repeater.
2-4. How to Connect Communication with SDI-12
Connect the output cable terminal to voltmeter or data logger with corresponding wire colors
described below. Make sure the cable length between the connecting slave [such as
pyranometers] and data collecting device to be less than 60m.
Shield must be connected, or noise may occur.
Also see 7-3. Output Cable for cable arrangements
Figure 5-5. Communication Connection with SDI-12
Figure 5-4. Communication Connection with Modbus RTU
SDI-12 Data
DC-12V+
Ground
Slave
No.n
Slave
No.1
Slave
No.2
Slave
No. 3
Data collection
Device

EKO INSTRUMENTS CO., LTD. - Pyranometer MS-40/40S - Instruction Manual Ver. 4
Pg. 18
2-5. Wire Assignments
Also see [7-3. Output Cables].
Table 5-3. Wire Color Codes [MS-40]
Table 5-4. Color Codes of cable [MS-40S]
No.
Cable Color
4-20mA
Modbus
SDI-12
0-1V *
1.
Brown
DC 5 to 36V [+]
DC 5 to 36V [+]
DC12V
DC 5 to 36V [+]
2.
White
4-20mA [-]
/ GND
GND
GND
0-10mA[-]
/ 0-1V[-] / GND
3.
Blue
---
RS485/B/+
SDI-12 Data
---
4.
Black
---
RS485/A/－
---
---
5.
Gray
4-20mA [+]
---
---
0-10mA[+]
/ 0-1V[+]
Shield
Shield
FG
FG
FG
FG
*When selecting 0-1V output, a precision resistor is required separately. The output depends on the
accuracy of the resistor.
No.
Cable Color
MS-40
1.
White
mV [+]
2.
Black
mV [-]
Shield
Shield
FG
Figure 5-6. Connector pin number of MS-40S
Each number corresponds to the number in Table 5-4.

EKO INSTRUMENTS CO., LTD. - Pyranometer MS-40/40S - Instruction Manual Ver. 4
Pg. 19
5-3. Measurin g S olar Irradiance
1. Solar Irradiance Measurement
1) In case of MS-40 [mV output]:
Global solar Irradiance [W/m2] can be determined by measuring the output voltage [mV] divided by the
individual sensor sensitivity [μV/W・m-2]. The output voltage is measured by a measuring device such as
voltmeter or data logger. If solar irradiance is measured continuously, it is recommended to use data
logger, which has sufficient recording capacity and calculation function.
Procedure for solar irradiance measurement is described below:
a. Configuration with a Data logger
If the measurement range can be selected on the data acquisition system, select the measurement
range, which can accurately measure the signal over a range of 0 to 20mV. The solar irradiance
assumed that it does not exceed 1,400W/m2 in both horizontal and tilted measurement positions.
The maximum output voltage can be calculated by multiplying the maximum solar irradiance with the
calibration factor [e.g. when the sensitivity of the MS-40 pyranometer is about 10μV/W・m-2 or
0.010mV/W・m-2, the maximum output voltage is about 1,400W/m2 times 0.010mV/W・m-2 = 14mV].
b. Calculate the Solar Irradiance [W/m2].
The solar irradiance in Watts per meter squared [W/m2] is obtained when the output voltage E [μV] is
divided by the sensitivity of the pyranometer S [μV/W・m-2]. This calculation is expressed by the
following formula:
I [W/m2] =
*The sensitivity S for the pyranometer is stated on the calibration certificate and the product label.
2) In Case of MS-40S [4-20mA Output]
a. Configure the Measurement Range
If the measurement range can be selected on the data acquisition system, select the measurement
range, which can accurately measure the signal within a range of 4 to 20mA. The global
broad-band solar irradiance assumed that it does not exceed 1,400W/m2 in both horizontal and
tilted measurement positions. When this is converted into MS-40S output, the result will be 20mA
[default]. The output for the MS-40S [4-20mA output] is set to be 1,600W/m2 at 20mA.
b. Calculate the Solar Irradiance [W/m2]
When the solar irradiance current value is A [mA], the solar irradiance I [W/m2] can be determined
by the following formula:
I [W/m2] =
Sa=0.01 (default setting)
A [mA] - 4
Sa [mA/W･m-2]
E [μV]
S [μV/W･m
-2
]

EKO INSTRUMENTS CO., LTD. - Pyranometer MS-40/40S - Instruction Manual Ver. 4
Pg. 20
3) MS-40S [0-1VOutput]
a. Setup the measurement range on the measuring device.
If the measurement range can be selected, chose the range which can measure between 0 to 1V
accurately.
Same for installing either in slope or horizontally, maximum solar irradiance is considered at
1,400W/m2, thus it is setup [default] so that the output of MS-40S [0-1V conversion] should be
1,600W/m2 at 1V.
b. Calculate the Solar Irradiance [W/m2]
When the solar irradiance voltage value is V [V], the solar irradiance I [W/m2] can be determined by
the following formula:
I [W/m2] =
Sv=1/1,600 (default setting)
4) MS-40S [Modbus RTU Output, SDI-12 Output]
When using the digital output (Modbus or SDI-12) by default the irradiance conversion is performed
on-board and is one of the measurement parameter within the data string.
2. Integration of Measurement Value:
In continuous operation mode the pyranometer is usually connected to a programmable data logger system.
Hence, sampling rates and data reduction methods can be defined right at the beginning of the data
acquisition process.
The response time that is given in the specifications of the EKO pyranometers states the amount of time,
which is necessary to reach 95% of the final measurement value. It is also possible to define a 63.2%
response [which is equal to 1-1/e]. This time constant, represented by the symbol τ, is 3 times smaller than the
values specified by EKO. The recommended[1] sampling rate for pyranometers is smaller than τ. So, for EKO
pyranometers, the sampling rates that have to be programmed in the data logger systems should not exceed
the values as given in Table 7-1.
Performing averaging and/or integration of measurement data can be meaningful to, e.g., reduce the data
volume or to meet application-specific requirement. Note that shorter sampling rates allow to use shorter
averaging/integration times [example for MS-40: <10 second sampling rate, 1 minute averaging period]. It
could also be meaningful to store not only average values, but to keep track of all statistical values during the
averaging period, namely: average, integral, minimum and maximum values, and standard deviation.
As a general recommendation, the averaging/integration period should be as short as possible, but long
enough to reduce the data volume to store the processed data safely.
[1]“Guide to Meteorological Instruments and Methods of Observation”, WMO reference document No. 8.
Examples:
The total daily radiant energy in Joule per meter squared [J/m2] is obtained by integrating the solar irradiance
over time. To calculate the total daily radiant energy in Joule per meter square [J/m2], multiply the averaged
solar irradiance I [W/m2] by the averaging interval period [s]. Then sum-up the total data number [n] of
averaged data points in one day.
Its physical unit is expressed with [J/m2] and can be calculated with J = W・S
V [V]
Sv [V/W･m-2]