Hukseflux

Thermal Sensors

USER MANUAL SR30-M2-D1
Digital Class A pyranometer with heating
and tilt sensor
compliant with IEC
61724-1 Class A

Copyright by Hukseflux | manual v2304 | www.hukseflux.com | info@hukseflux.com

Cautionary statements
Cautionary statements are subdivided into four categories: danger, warning, caution andnotice according to the severity of the risk.
DANGER
Failure to comply with a danger statement will lead to death or serious
physical injuries.

WARNING
Failure to comply with a warning statement may lead to risk of death orserious physical injuries.

CAUTION
Failure to comply with a caution statement may lead to risk of minor ormoderate physical injuries.

NOTICE
Failure to comply with a notice may lead to damage to equipment or may
compromise reliable operation of the instrument.

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Contents
Cautionary statements
Contents
List of symbols
Introduction
1
Ordering and checking at delivery
1.1
Ordering SR30-M2-D1
1.2
Included items
1.3
Quick instrument check2
Instrument principle and theory
2.1
Why a “spectrally flat” pyranometer?
2.2
Operating modes: use of power - heating
2.3
Overview of remote diagnostics
2.4
Use of the tilt sensor
3
Specifications of SR30-M2-D1
3.1
Specifications of SR30-M2-D1
3.2
Dimensions of SR30-M2-D1
4Standards and recommended practices for use
4.1
Classification standards
4.2
General use for solar radiation measurement
4.3
Specific use for outdoor PV system performance testing
4.4
Specific use in meteorology and climatology
4.5
General use for sunshine duration measurement
5
Installation of SR30-M2-D1
5.1
Site selection and mechanical installation
5.2
Installation of the sun screen
5.3
Installation of optional mounts
5.4
Electrical installation
5.5
Internal protection
5.6
Connecting to an RS-485 network
5.7
Electrical isolation, grounding and shield connection
5.8
Cabling requirements
5.9
A PC as RS-485 master6
Communication with SR30-M2-D1
6.1
PC communication: Hukseflux Sensor Manager software
6.2
Network communication: getting started
6.3
Changing the device address and serial communication settings
7
Use of remote diagnostics
7.1
Recommendations
7.2
Sensor body temperature
7.3
Tilt angle
7.4
Internal relative humidity
7.5
Heater current
7.6
Ventilator current
7.7
Ventilator speed

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8
Making a dependable measurement
8.1
The concept of dependability
8.2
Reliability of the measurement
8.3
Repair and maintenance
8.4
Uncertainty evaluation
9
Maintenance and trouble shooting
9.1
Recommended maintenance and quality assurance
9.2
Trouble shooting
9.3
Calibration and checks in the field
9.4
Data quality assurance
10
Appendices10.1 Appendix on tools for SR30-M2-D1
10.2 Appendix on spare parts for SR30-M2-D1
10.3 Appendix on the ventilator
10.4 Appendix on standards for classification and calibration
10.5 Appendix on calibration hierarchy
10.6 Appendix on meteorological radiation quantities
10.7 Appendix on ISO and WMO classification tables
10.8 Appendix on ISO 9060:1990 classification no longer valid
10.9 Appendix on definition of pyranometer specifications
10.10 Appendix on terminology / glossary
10.11 Appendix on function codes, register and coil overview
10.12 Appendix on electromagnetic compatibility (EMC) testing
10.13 EU declaration of conformity

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List of symbols
Quantities

SymbolUnit

Sensitivity
Temperature
Solar irradiance
Plane of Array irradiance
Solar radiant exposure
Time in hours
Tilt angle relative to horizontal
Relative humidity
Pressure

S
T
E
Gi
H
h
θh
RH
p

V/(W/m2)
°C
W/m2
W/m2
W∙h/m2h°%barTemperature coefficient
Temperature coefficient
Temperature coefficient

a
b
c

1/°C²
1/°C
-

(see also appendix 10.6 on meteorological quantities)
Subscripts
extended RS-485 common mode range
DC isolation voltage (instrument body to signal ground)
heater power

Vcm, max
Viso
Pheater

Acronyms
ASTM
CRC
GHI
IEC
ISO
LSW
MSW
POA
PV
RPM
SCADA
WMO

American Society for Testing and Materials
Cyclic Redundancy Check
Global Horizontal IrradianceInternational Electrotechnical Commission
International Organization for Standards
Least-Significant Word
Most-Significant Word
Plane of Array
Photovoltaic
Rounds-per-MinuteSupervisory Control And Data Acquisition
World Meteorological Organization

Modbus® is a registered trademark of Schneider Electric, licensed to the Modbus Organization, Inc.

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Introduction
Welcome to the next level in solar radiation monitoring! The all-digital heated SR30-M2-D1
pyranometer offers the highest accuracy and highest data availability: it outperforms
pyranometers equipped with traditional ventilation systems.
After introduction in 2017, SR30 was rapidly recognised as the ideal instrument for use in
PV system performance monitoring, and is increasingly used in meteorological networks
as well.
SR30 is an ISO 9060 spectrally flat Class A pyranometer. It measures the solar radiation
received by a plane surface, in W/m2, from a 180 o field of view angle. SR30 offers
several advantages over competing pyranometers:• The first pyranometer compliant in its standard configuration with the IEC 61724-1
Class A requirements• Heated for best data availability: RVH TM (Recirculating Ventilation and Heating)technology outperforms traditional pyranometer ventilation• Lowest total cost of ownership: supported by a worldwide calibration organisation• Spectrally flat: WMO compliant, also suitable for Plane of Array, diffuse, and albedo
measurement

Figure 0.1 SR30 digital spectrally flat Class A pyranometer with heating and tilt sensor.
NOTICE
This manual supports model SR30-M2-D1, the successor of SR30-D1.
Need support for the discontinued SR30-D1? Please refer to its separate manual.

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SR30 offers several advantages over competing pyranometers:

PV System performance monitoring: IEC 61724-1 Class A compliant
SR30 complies, without the need for additional accessories, with IEC requirements. It
includes heating for dew and frost mitigation. The instrument has 2 heating modes;
normal at < 3 W, and medium at < 0.65 W power.

Lowest total cost of ownership
Customers prefer Hukseflux pyranometers for their unsurpassed measurement accuracy
and their lowest total cost of ownership. Total costs are mainly determined by costs of
installation, on-site inspections, servicing and calibration:
•

•

•
•

pyranometers must be calibrated every 2 years. Such recalibration is considered goodpractice for any measuring instrument and is required by ISO, IEC and WMO
standards covering PV system performance - and meteorological monitoring. Cost ofrecalibration, however, can be high. Hukseflux’ worldwide calibration network will
help you reduce these costs. Learn more about Hukseflux pyranometer calibration
services.
low demand on infrastructure: SR30’s RVHTM (Recirculating Ventilation and Heating)technology requiresless than 3 W power, compared to 10 W for traditional ventilation
systems.
reduction of unnecessary on-site inspection by remote diagnostics.
reduction of unnecessary repair costs using a dome protector (see below).

Supplied with dome protector
Damaged domes used to be a significant cause of pyranometer malfunction. The DP01
dome protector:• mitigates the risk of damage to the pyranometer dome
• reduces unnecessary repair costs
We recommend to use DP01 during initial transport and installation at the measurementsite. After that, DP01 can be stored. It is used again, typically every 2 years, when thepyranometer is removed and sent to an external laboratory for calibration.
Using DP01 is easy. The protector is mounted with a double snap fit connection to thepyranometer. To remove the DP01, press both sides of the protector.
Please do not forget to remove DP01 before you start measuring.
More information about the DP01.

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Figure 0.2 SR30 is supplied with a DP01 dome protector.

Calibrated tilt angle measurement
SR30 includes a tilt sensor. This is very practical for remote checks of instrument
installation.
For PV systems with single-axis trackers, IEC 61724-1 Class A systems also require a tilt
angle measurement.
The IEC suggested option to measure tilt by counting motor steps does not detect tracker
faults, which is one of its purposes. Also, counting steps will not lead to the required 1 ˚accuracy (Clause 10.1). Every SR30 tilt sensor is individually calibrated and temperaturecompensated between -30 and +50 ˚C, resulting in a high accuracy of < 1 ˚.

“Spectrally flat” as required for PV monitoring and meteorology
The new ISO 9060 defines pyranometer classes A, B and C. The standard also adds a
new subclass, called “spectrally flat”. The vast majority of users need to use instrumentsof the spectrally flat subclass; only spectrally flat instruments measure with highaccuracy, also when a cloud obscures the sun, or when the irradiance includes reflectedradiation. These situations occur for example when you measure Global Horizontal
irradiance (GHI) under partly or fully cloudy skies, when you measure Plane of Array

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(POA), albedo or net-radiation. Instruments of just class A, B or C, and not spectrally
flat, only measure accurately under clear sky conditions.
Using "spectrally flat" instruments is essential because this ensures:
•
•
•
•
•

you can measure accurately not only horizontally under clear-sky conditions, but also
general GHI, POA, albedo and net radiation
you comply with WMO requirements
you can use the normal standardised ISO and WMO calibration procedures
you can also measure separately the diffuse component only (creating a
diffusometer) with a shadow ring or shading ball, using the same instrument model
you can perform uncertainty evaluations with negligible (zero) spectral errors

See Section 2.1 in this manual for a more detailed explanation.

Heated for high data availability
High data availability is attained by heating of the outer dome by ventilating air between the innerand outer dome. This space forms a closed circuit together with the instrument body; ventilated air
is not in contact with ambient air. RVH TM - Recirculating Ventilation and Heating - technology,
developed by Hukseflux, mitigates dew and frost and is as effective as traditional ventilation
systems, without the maintenance hassle and large footprint. The instrument has 2 heating

modes; normal at < 3 W, and medium at < 0.65 W power.
••

low power consumption:
SR30-M2-D1 requires less than 3 W, compared to 10 W for traditional ventilation
systems
low maintenance:
SR30-M2-D1 does not require filter cleaning or replacement

The dome of the SR30 pyranometer is heated by ventilating the area between the innerand outer dome. RVH TM is much more efficient than traditional ventilation, where most of
the heat is carried away with the ventilation air. Recirculating ventilation is as effective insuppressing dew and frost deposition at less than 3 W as traditional ventilation is at 10
W. RVH TM technology keeps domes and sensor in perfect thermal equilibrium, which also
leads to a reduction of zero offsets.

Environmental impact
We analysed the environmental impact of SR30 by comparison to externally ventilated
pyranometers ( SR20 + VU01). SR30’s impact is lower due to:••lower power consumption during use
lower transport volume when first installed and when recalibrated every 2 years

Take a look at our environmental impact analysis.
As a user reduce environmental impact by:••

nearby calibration, minimising transport
power heaters only if needed

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Liabilities covered: test certificates
As required by ISO 9060 for Class A classification, each SR30 is supplied with calibrationand test results:••••

sensitivity
directional response
temperature response
tilt sensor response (0 to 90 o)

Figure 0.2 Heated to counter frost anddew deposition: clear difference between
a non-heated pyranometer (back) and
SR30 with RVH TM technology (front).

Liabilities covered: test certificates

Figure 0.3 SR30 includes a digital tilt
angle measurement, very practical for
remote checks of instrument orientation.
The image shows two SR30’s in PV systemmonitoring, one measuring in Plane of Array(POA).

Improved electronics
Model SR30-M2-D1 is the successor of the popular SR30-D1 and offers improved
electronics design over its predecessor.

Operation in 3 power modes
Heater and ventilation may be remotely switched on and off. The instrument has 2
heating modes; normal at < 3 W, and medium at < 0.65 W power. Operation without
heating is also possible, in the low power mode at < 0.1 W. With decreasing power the
mitigation of dew and frost will become weaker. However, overall performance in all 3
modes will comply with the ISO 9060 Class A classification.

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Remote sensor diagnostics
Besides solar radiation, SR30 outputs sensor diagnostics, including:
•
•
•
•
•
•
•

instrument temperaturetilt angle
ventilator speed (RPM)
internal humidity
internal pressure
ventilator current
heater current

Remote diagnostics permits real-time status monitoring, reducing the need for(un)scheduled field inspections.

Suggested use
Suggested use for SR30:• PV system performance monitoring• scientific meteorological observations

Diffuse radiation measurement
With its outstanding zero offset specification and the fact that it is spectrally flat, SR30 isalso the instrument of choice for high-accuracy diffuse radiation measurement.

Communication with a PC: Hukseflux Sensor Manager software
For communication between a PC and SR30, the Hukseflux Sensor Manager software canbe downloaded. It allows the user to plot and export data, and change the SR30 Modbus
address and its communication settings. Also, the digital outputs may be viewed forsensor diagnostics.
See our separate Sensor Manager user manual.

Figure 0.4 Improved Sensor Manager software allows the user to change the Modbus
address and communication settings.

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SR30 design
SR30 pyranometer employs a state-of-the-art thermopile sensor with black coatedsurface, two domes and an anodised aluminium body. SR30 offers a digital output via
Modbus RTU over 2-wire RS-485. The pyranometer dome is heated by ventilating thespace between the inner and outer dome using RVH TM - Recirculating Ventilation andHeating - technology.

Options for mounting and levelling
There are several mounting options available for SR30: a levelling mount and a tube
levelling mount. They allow for simplified mounting, levelling and instrument exchange
on either a flat surface or a tube.

Figure 0.5 Optional levelling mount (picture on the left); a practical spring-loaded mountfor easy mounting, levelling and instrument exchange on flat surfaces, and the optional
tube mount (picture on the right) including spring-loaded levelling upper clamp, lower
clamp for tube mounting and two sets of bolts.

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Spring-loaded levelling
When opting for one of the levelling mounts, SR30 is easily mounted and levelled using
the mount’s spring-loaded centre bolt and SR30’s adjustable levelling feet.

Figure 0.6 Optional levelling mount allows spring-loaded levelling.

Figure 0.7 Hukseflux PMF series pyranometer mounting fixtures can be used for easy
installation of pyranometers. On the left, PMF01 pyranometer mounting fixture with one
SR30, and on the right PMF02 with two SR30 pyranometers. Both fixtures allow mounting in
Plane of Array for PV system performance monitoring and meteorological applications.

See also
•
•
•
•
•
•
•
•

SRA30 albedometer consisting of two SR30’s
SR05, an economical solution often used for monitoring small scale PV systems
PMF series mounting fixtures
consult our pyranometer selection guide
introduction of SR30 on our YouTube channel
environmental impact analysis of SR30
why ventilate and heat pyranometers
view our complete range of solar sensors

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Cabling
The standard cable length is 5 m. Optionally cables of 10 and 20 m are supplied. It isgood practice to keep cables as short as possible; see chapter on cabling requirements.

Figure 0.8 SR30 standard cable with M12-A female connector on sensor end. On the
opposite end (not visible), the cable is terminated with removed sheath over 0.15 m;
stranded copper conductors with plastic insulators, stripped ends with ferrules. Its length is
5 metres standard and it is available in 10 and 20 metres too.
SR30 is designed for use in SCADA (Supervisory Control And Data Acquisition) systems,
supporting Modbus RTU (Remote Terminal Unit) protocol over RS-485. In these networks
the sensor operates as a Modbus RTU slave. SCADA systems are often implemented inphotovoltaic solar energy (PV) systems and meteorological networks. Using SR30 in a
network is easy. Once the Modbus address and communication settings have been
configured and connected to a power supply, the instrument can be used in RS-485
networks. The user should have sound knowledge of the Modbus communication protocol
when installing sensors in a network.

Recommended practice for use
The instrument should be used in accordance with the recommended practices of ISO,WMO and ASTM. See chapter 4 for more detailed recommendations.

Recalibration
The recommended calibration interval of pyranometers is 2 years. The registers
containing the applied sensitivity and the calibration history of SR30 are fully accessible
for users. This allows the user to choose his own local calibration service. Learn more
about Hukseflux pyranometer calibration services.

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1 Ordering and checking at delivery
1.1

Ordering SR30-M2-D1

The standard configuration of SR30-M2-D1 is with 5 metres cable.
Common options are:••••longer cable; 10 and 20 metreslevelling mount. Specify article number LM01
tube levelling mount with set of bolts. Includes LM01. Specify article number TLM01
set of 10 dome protectors DP01

Table 1.1.1 Ordering codes for SR30.
VERSIONS OF SR30 (part numbers)
SR30-M2-D1

SR30-M2-D1-LM01

SR30-M2-D1-TLM01

digital spectrally flat Class A (secondary standard)
pyranometer, with heating, internal ventilation, tilt sensor
and Modbus over RS-485 output
digital spectrally flat Class A (secondary standard)
pyranometer, with heating, internal ventilation, tilt sensor,
Modbus over RS-485 output and with levelling mount, forspring-loaded levelling and mounting SR30 on a surface
digital spectrally flat Class A (secondary standard)
pyranometer, heating, internal ventilation, tilt sensor,
Modbus over RS-485 output and with tube levelling mount,for spring-loaded levelling and mounting SR30 on a tube

CABLES FOR SR30
with M12-A female connector on sensor end, and on the opposite end cable terminatedwith removed sheath over 0.15 m; stranded copper conductors with plastic insulators,
stripped ends with ferrules.
‘-05’ after SR30 part number
standard cable length: 5 m‘-10’ after SR30 part number
cable length: 10 m‘-20’ after SR30 part number
cable length: 20 m
CABLE WITH CONNECTOR PAIR
with male and female M12-A connectors
C07E-20
SET OF 5 DOME PROTECTORS
DP01 set of 5

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cable length: 20 m
in bag containing 5 pieces DP01

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1.2

Included items

Arriving at the customer, the delivery should include:
pyranometer SR30-M2-D1
sun screen
dome protector
cable of the length as ordered
product certificate matching the instrument serial number, including:o calibration certificate
o temperature response test reporto directional response test reporto tilt sensor test report• any other options as ordered
•
•
•
•
•

For SR30-M2-D1-LM01, also
• spring-loaded levelling mountFor SR30-M2-D1-TLM01, also
• spring-loaded levelling mount• lower clamp to mount SR30 to a tube or mounting rod• 2 sets of bolts for different tube diameters
Please store the certificates in a safe place.
The latest version of the Hukseflux Sensor Manager can be downloaded via
www.hukseflux.com/downloads

1.3

Quick instrument check

A quick check of the instrument can be done by connecting it to a PC and installing the
Sensor Manager software. See the chapters on installation and PC communication for
directions. Please note that a separate power supply is required; the sensor cannot be
powered from a USB port.
1. At power-up, the signal may have a temporary output level different from zero; anoffset. Let this offset settle down; it is a normal part of the power-up procedure.
2. Take the dome protector off. Check if the sensor reacts to light: expose the sensor toa strong light source, for instance a 100 W light bulb at 0.1 m distance. The signal should
read > 100 W/m2 now. Darken the sensor either by putting something over it orswitching off the light. The instrument irradiance output should go down and within one
minute approach 0 W/m2.
3. Inspect the bubble level, compare to the tilt angle output.
4. Verify heater current, ventilator speed, internal humidity.
5. Inspect the instrument for any damage.
6. Check the instrument serial number as indicated by the software against the label on
the instrument and against the certificates provided with the instrument.

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2 Instrument principle and theory
5

3

1

6

7

8

9

10

4

2

11

12
13

14

15

Figure 2.0.1 Overview of SR30:
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
(11)
(12)
(13)
(14)
(15)

cable (standard length 5 metres, optional longer cable)
connector
sun screen
bubble levelbubble level windowouter dome
inner dome
thermal sensor with black coatinginternal ventilation vents
quick release system of sun screen
instrument bodylevelling feet
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SR30’s scientific name is pyranometer. A pyranometer measures the solar radiation
received by a plane surface from a 180 ° field of view angle. This quantity, expressed in
W/m2, is called “hemispherical” solar radiation. The solar radiation spectrum extends
roughly from (285 to 3000) x 10-9 m. By definition a pyranometer should cover thatspectral range with a spectral selectivity that is as “flat” as possible.
In an irradiance measurement by definition the response to “beam” radiation varies withthe cosine of the angle of incidence; i.e. it should have full response when the solar
radiation hits the sensor perpendicularly (normal to the surface, sun at zenith, 0 ° angle
of incidence), zero response when the sun is at the horizon (90 ° angle of incidence, 90 °zenith angle), and 50 % of full response at 60 ° angle of incidence. A pyranometershould have a so-called “directional response” that is as close as possible to the ideal
cosine characteristic (older documents mention the term “cosine response” instead).
In order to attain the proper directional and spectral characteristics, SR30’s main
components are:•a thermal sensor with black coating. It has a flat spectrum covering the (200 to
50 000) x 10-9 m range, and has a near-perfect directional response. The coating
absorbs all solar radiation and, at the moment of absorption, converts it to heat. The
heat flows through the sensor to the sensor body and from the sensor body to theenvironment. The thermopile sensor generates a voltage output signal that is
proportional to the solar irradiance.

•

in case of SR30, the analogue thermopile voltage is converted by the instrument
electronics to a digital signal. In this process the temperature dependence of thethermopile is compensated. SR30 uses high-end conversion electronics with a verysmall temperature dependence and excellent long-term stability.

•a glass dome. This dome limits the spectral range from (285 to 3000) x 10-9 m(cutting off the part above 3000 x 10-9 m), while preserving the 180 ° field of view
angle. Another function of the dome is that it shields the thermopile sensor from theenvironment (convection, rain).

•a second (inner) glass dome: For a spectrally flat Class A pyranometer, two domes
are used, and not one single dome. This construction provides an additional “radiation
shield”, resulting in a better thermal equilibrium between the sensor and inner dome,
compared to using a single dome. The effect of having a second dome is a strong
reduction of instrument thermal offsets.

•a heater and ventilator: in order to reduce dew deposition and frost on the outer dome
surface, SR30 has a built-in heater and ventilator. The heater is attached to the sensor
body. The ventilation air circulates inside the body and between the domes. The
combination of ventilation and heating keeps the domes in thermal equilibrium with thethermopile sensor and above dew point. When ventilation is [ON], zero offsets are verylow.

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•

a tilt sensor: this sensor measures tilt with a ± 1 ° uncertainty and a short-term
resolution, or detection limit, of 0.1 °. This is sufficient to monitor incidents thatchange the instrument tilt.

Pyranometers can be manufactured to different specifications and with different levels of
verification and characterisation during production. The ISO 9060:2018 standard, “Solarenergy - specification and classification of instruments for measuring hemispherical solarand direct solar radiation”, distinguishes between 3 classes; spectrally flat Class A(highest accuracy), Class B (second highest accuracy) and Class C (third highest
accuracy).

relative spectral content /response [arbitrary units]

From class C to class B and from class B to class A, the achievable accuracy improves
roughly by a factor 2.

1.2
1

solar radiation

0.8

pyranometer
response

0.6
0.4
0.2
0
100

1000

10000

wavelength [x 10-9 m]

Figure 2.0.2 Spectral response of the pyranometer compared to the solar spectrum. The
pyranometer only cuts off a negligible part of the total solar spectrum.

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deviation from ideal cosine response [%]

4

South

3
West

2
1

East
0

0

20

40

60

-1

80
North

-2
-3
-4

zenith angle [°]ISO 9060
specification
limit
specification limit
secondarystandard
spectrally flat
Class Apyranometerpyranometer

Figure 2.0.3 Directional response of an SR30 pyranometer of 4 azimuth angles,
compared to spectrally flat Class A limits.

2.1 Why a “spectrally flat” pyranometer?
ISO 9060:2018 defines classes A, B and C. The standard also defines a subclass, called"spectrally flat". The vast majority of users need to use instruments of the spectrally flat
subclass; only spectrally flat instruments measure with high accuracy, also when a cloud
obscures the sun, or when the irradiance includes reflected radiation. These situations
occur when measuring Global Horizontal Irradiance (GHI) under partly or fully cloudy
skies, Plane of Array (POA) and albedo or net-radiation. Instruments of class A, B or C
that are not spectrally flat only measure accurately under clear skies in a horizontal
position.
Compliance with the spectrally flat subclass also means the instrument complies withWMO guide and keeps continuity with the 1990 version of ISO 9060. The classification"spectrally flat" may be added to the name of the class if the instrument fulfils spectral
criteria as in the WMO guide and ISO 9060:1990 (the preceding version of the same
standard dating from 1990) “secondary standard pyranometers” (i.e. spectral selectivity(350 to 1500) x 10-9 m: < ± 3 % with 2 % guard band).
The spectral error of ISO 9060:2018 is defined as "Clear sky global horizontal irradiancespectral error". This error is valid under a clear sky. This is not the common spectrum innormal application in solar renewable energy and it is also not the common spectrum inmeteorological application. Even for frequently occurring situations, for example when aSR30-M2-D1 manual v2304

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cloud obscures the direct sun or under a cloudy sky, the measurement error with anormal class A, B or C pyranometer is undefined. This is why almost all users need a"spectrally flat" pyranometer, for which this error is negligible.
To conclude, specifying "spectrally flat" is essential because this ensures:
•

•

•

•

•

•

you can measure accurately not only clear sky (with direct solar radiation) GHI in ahorizontal position, but also when a cloud obscures the sun, blue sky diffuse only,
cloudy sky diffuse, reflected, Plane of Array, POA, for Photovoltaic solar panels,
albedo or net radiation for meteorology.
you comply with WMO: spectrally flat Class A and B instruments comply with the
WMO spectral requirements of high quality pyranometers as well as with the WMO
network requirement to measure not only global horizontal, but also reflectedradiation. Normal Class A and B instruments do not comply with WMO requirements.
you can use the normal standardised ISO and WMO calibration procedures, and canbenefit from relatively low-cost indoor calibrations. For normal class A, B and C
instruments this is not possible.
you comply with the WMO Guide to Meteorological Instruments and Methods ofObservation, and the preceding ISO 9060 version of 1990, attain continuity of
performance and specifications.
you can also measure separately the diffuse component only (creating a
diffusometer) for example with a shadow ring or shading ball, using the same
instrument model.
you can perform uncertainty evaluations with negligible (zero) spectral errors under
all conditions, because they are calibrated out.

Figure 2.1.1 Heating: how it’s done: recirculating ventilation and heating between the
inner- and outer dome forming a closed circuit with the body is much more powerefficient than traditional ventilation systems.

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2.2

Operating modes: use of power - heating

A unique feature of SR30 is its built-in heater. In practice, this is as effective against dew
and frost deposition as using traditional ventilation systems.
The heater is attached to the sensor body. Heat is generated inside the sensor body. The
ventilator circulates air inside the body and between the domes. The combination ofventilation and heating keeps the domes in thermal equilibrium with the sensor and theentire instrument above dew point. When ventilation is [ON], zero offsets are very low.
There are 3 power modes: normal, medium and low power mode. The normal andmedium power mode are “heated” in the sense that in these modes power consumption
is sufficient to mitigate dew and frost. In the low power mode, power consumption is not
sufficient to mitigate dew and frost.
In normal power mode, both heater and ventilator are [ON], in medium power mode,
only the ventilator is [ON], in low power mode both are [OFF]. Table 2.1.1 gives an
overview of these settings and our recommendations for use.
Table 2.2.1 Possible user scenarios for the heater and ventilator.
power
mode

heaterstatusventilator
statuspower
consumption(at 12 VDC)
< 3.0 Wdew andfrost
mitigation
excellent

Normal

[ON]

[ON]

N/A

[ON]

[OFF]

Medium

[OFF]

[ON]

< 0.65 W

not under
extremeconditions

Low

[OFF]

[OFF]

< 0.1 Wnocomment

factory default
recommended settings
do not use thesesettings, spectrally flat
Class A specifications will
not be met
this mode offers themost accurate
measurement results
because the sensitivity tothermal fluctuations of
the environment issmallerrecommended over the[OFF] [OFF] setting,because it reduces thethermal sensor offset
spectrally flat Class A
performance is also
guaranteed with thesesettings

Heating when used in combination with ventilation does not affect the classification
specifications and the measurement accuracy.

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When using the heater without ventilation, spectrally flat Class A specifications will not be
met, because of a heating-induced offset.
In case that there is no danger of deposition of dew or frost, the medium power mode
(using the ventilator but not the heater) offers the most accurate measurements overshort time intervals. Averages on the minute time scale produce the same result as in
the normal power mode. The measurement in medium power mode is less sensitive tothermal shocks (rapid changes of the sensor body temperature) and is less noisy.
The nominal ventilator power is about 0.5 W and the heater power is 1.5 W, see section
7.5 for more detail. With around 0.1 W power to the electronics and efficiency variations
over temperature and operating voltage the total operation power consumption is < 3 W.
NOTICEDo not use SR30 with heater [ON] and ventilator [OFF].
This is not a valid operating mode. ISO 9060:2018 spectrally flat class A
specifications will not be met in this operating mode.

2.3

Overview of remote diagnostics

Besides the digital output measuring irradiance in W/m2, SR30 has several internalsensors providing outputs which may be used for remote diagnostics. Remote monitoringof the instrument’s condition helps improve the accuracy and reliability of themeasurement. It also allows to improve preventive maintenance and effective trouble
shooting. Chapter 7 gives recommendations on how to use these diagnostics. Chapter 6
contains details on the register structure, needed for reading the remote diagnostics
output.
A brief overview of the diagnostic signals:
•
•
•
•
•
•
•

tilt angle
sensor body temperatureinternal humidity
internal pressure
ventilator speed
ventilator current
heater current

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2.4

Use of the tilt sensor

SR30 is equipped with an internal tilt sensor. The tilt measurement serves to monitor
slow, long-term changes as well as incidents that cause the instrument to move. The
absolute accuracy of the sensor depends on temperature and is not as high as that of the
bubble level. The bubble level remains the reference for horizontal installation. The shortterm resolution, or detection limit, of the tilt sensor is sufficiently high for monitoring
possible incidents. Table 2.4.1 gives recommendations for using the tilt sensor.
Table 2.4.1 Recommendations for use of the tilt sensor.
Application

Requiredaccuracy±1°

Reference

Remarks

tilt sensor

tilt measurement is sufficiently accurate

Horizontal
installation
Short-term incident
monitoring± 0.1 °

bubble level± 0.1 °

tilt sensor output,
immediately after
installation

Long-termmonitoring±1°

tilt sensor output,
immediately after
installation

tilt measurement is not sufficiently
accurate
after levelling with the bubble level, store“tilt angle” register. This stored
measurement is the reference formonitoring incidents.
for short-term incident monitoring, markchanges or generate a warning if the tilt
sensor measurement exceeds 0.2 °/ min.
for long term monitoring, mark changes orgenerate a warning if the tilt sensor
measurement exceeds 1 °.

Tilted installation

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3 Specifications of SR30-M2-D1
3.1

Specifications of SR30-M2-D1

SR30-M2-D1 measures the solar radiation received by a plane surface from a 180 o field ofview angle. This quantity, expressed in W/m2, is called “hemispherical” solar radiation.
SR30 offers irradiance in W/m2 as a digital output. SR30-M2-D1 must be used in combination
with a suitable power supply and a data acquisition system which uses the Modbus RTU
communication protocol over an RS-485 connection. When operated in one of the valid
operating modes, the instrument is classified as spectrally flat Class A according to ISO 9060
and compliant with IEC 61724-1 requirements for use in Class A monitoring systems.
NOTICE
This manual supports model SR30-M2-D1, the successor of SR30-D1.
Need support for the discontinued SR30-D1? Please refer to its separate manual.

Table 3.1.1 Specifications of SR30-M2-D1 (continued on next pages).
SR30-M2-D1 CLASSIFICATIONS
ISO classification (ISO 9060:2018)
spectrally flat Class A pyranometer
ISO classification (ISO 9060:1990)
secondary standard pyranometer
WMO performance level (WMO-No. 8, high quality pyranometerseventh edition 2008)
LIST OF CLASSIFICATION CRITERIA OF ISO 9060*
Response time (95 %)Zero offset a (response to 200 W/m2
net thermal radiation)- in normal power mode
- in medium power mode
- in low power mode
Zero offset b (response to 5 K/hchange in ambient temperature)
Zero offset c (total zero offset)- in normal power mode
- in medium power mode
- in low power mode
Non-stability
Non-linearity
Directional response
Directional response test of individual
instrument
Spectral selectivity
Clear sky global irradiance spectral error
Temperature response
Temperature response test of
individual instrument

SR30-M2-D1 manual v2304

3s< 2 W/m2< 2 W/m2< 5 W/m2< ± 2 W/m2
zero offset a + zero offset b + 1 W/m2
< 5 W/m2< 5 W/m2< 8 W/m2< ± 0.5 % change per year
< ± 0.2 % (100 to 1000 W/m2)< ± 10 W/m2
report included for 0 to 95° angle of incidence< ± 3 % ((0.35 to 1.5) x 10-6 m)< ± 0.5 %< ± 0.4 % (-30 to +50 °C)
report included

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Tilt response
Additional signal processing error< ± 0.2 % (0 to 90 ° at 1000 W/m2)
none (signal processing errors are included in otherspecifications)*For the exact definition of pyranometer ISO 9060 specifications, see the appendix.

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IEC 61724-1:2017 COMPLIANCE
IEC 61724-1:2017 compliance

SR30-M2-D1 manual v2304

meets Class A PV monitoring system requirements forsolar irradiance and tracker tilt angle measurements

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Table 3.1.1 Specifications of SR30 (continued on next pages).

SR30-M2-D1 ADDITIONAL SPECIFICATIONS
Spectral range(20 % transmission points)
Field of view angle
Technology employed
Heating
Ventilation
Dome protector
Standard operating mode
Max. power consumption
Output definition
Recommended data request interval
Measurement range
Zero offset steady state
Measurand
Measurand in SI radiometry units
Irradiance resolution
Uncertainty of the measurement

WMO estimate on achievable accuracy
for daily sums (see appendix for adefinition of the measurement conditions)
WMO estimate on achievable accuracy
for hourly sums (see appendix for adefinition of the measurement conditions)
Optional measurandMeasurement function / optional
programming for sunshine duration
Measurand
Sensor temperature measurement
uncertainty
Sensor temperature resolution
Measurand
Tilt measurement uncertainty
Tilt measurement range
Tilt sensor detection limit
Tilt sensor characterisation of individual
instrument
Levelling (see options)Levelling accuracy
Instrument tilt measurement uncertainty(285 to 3000) x 10-9 m
180 °Recirculating Ventilation and Heating (RVH TM)
includedincludedincluded (model DP01)
heater and ventilator [ON], normal power mode
< 3.0 W at 12 VDC
running average over 4 measurements, refreshed
every 0.1 s
1 s, storing 60 s averages-400 to 4000 W/m2
< ± 1 W/m2 (-40 to + 80 °C)
hemispherical solar radiation
irradiance in W/m2
0.05 W/m2
statements about the overall measurement
uncertainty can only be made on an individual basis.
see the chapter on uncertainty evaluation
2%

3%

sunshine duration
programming according to WMO guide paragraph
8.2.2
sensor body temperature± 0.5 °C
7.8 x 10-3 °C
sensor tilt angle± 1 ° (0 to 90 o tilt, -30 to + 50 °C)
0 to 180 °< 0.1 ° (smallest meaningfully detectable change in atime interval of < 10 min)report included (0 to 90 o tilt, -30 to + 50 °C)
bubble level and adjustable levelling feet are included< 0.1 ° bubble entirely in ring
± 1 ° (0 to 90 °)Table 3.1.1 Specifications of SR30-M2-D1 (started on previous pages).
Measurand

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sensor internal relative humidity

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Humidity sensor accuracy
Humidity sensor hysteresis
Measurand
sensor uncertainty
Measurand
Measurand
MeasurandStandards governing use of the
instrument± 3 % RH (for RH between 0 and 80 %)± 1 % RH
sensor internal pressure± 4 mbarheater current
ventilator current
ventilator speed in RPM
IEC 61724-1; Photovoltaic system performancemonitoring – guidelines for measurement, dataexchange and analysis
ISO/TR 9901:1990 Solar energy -- Field
pyranometers -- Recommended practice for use
ASTM G183 - 15 Standard Practice for Field Use of
Pyranometers, Pyrheliometers and UV Radiometers

MECHANICAL
Chassis connector
Mounting (see options)

Desiccant
Desiccant replacement
Ventilator replacement
Body material
Dome material
Gross weight including 5 m cable
Net weight including 5 m cable
ENVIRONMENT

M12-A male connector, 5-pole
2 x M5 bolt at 46 mm centre-to-centre distance on
north-south axis, requires 4 mm hex key
1x M6 bolt, centered
two bags of silica gel, 2 x 1 g< 5 year interval, typically replaced during calibration,
ask the manufacturer for instructions< 5 year interval,
ask the manufacturer for instructions
anodised aluminium
optical glass, N-BK7
approx. 1 kg
approx. 0.5 kg

Rated operating temperature range
IP protection classHEATING AND VENTILATION-40 to +80 °C
IP67Heater voltage
Rated heater current range
Nominal heater resistanceNominal heater power
Rated ventilator speed
ELECTRICAL

5 V (independent of supply voltage)
0.250 to 0.375 A
17 Ω
1.5 W
5000 to 10 000 RPM (uncontrolled)

Supply voltage range
8 to 30 VDC
Operating power<3W
OPERATION IN NORMAL POWER MODE
Heater and ventilator settings
Dew and frost mitigation
Zero offset aheater [ON] and ventilator [ON]yes
< 2 W/m2

Table 3.1.1 Specifications of SR30-M2-D1 (started on previous pages)

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Supply voltage range
8 to 30 VDCPower consumption< 3.0 W at 12 VDC
OPERATION IN MEDIUM POWER MODE
Heater and ventilator settings
Dew and frost mitigation
Zero offset a
Supply voltage range
Power consumption
OPERATION IN LOW POWER MODE

heater [OFF] and ventilator [ON]yes
2 W/m28 to 30 VDC< 0.65 W at 12 VDC

Heater and ventilator settings
Dew and frost mitigation
Zero offset a
Supply voltage range
Power consumption
CALIBRATION

heater [OFF] and ventilator [OFF]no5 W/m28 to 30 VDC< 0.1 W at 12 VDC

Calibration traceability
Calibration hierarchy

to WRR
from WRR through ISO 9846 and ISO 9847, applying
a correction to reference conditions
indoor calibration according to ISO 9847, Type IIc< 1.2 % (k = 2)
Hukseflux issues calibration certificates with content
limited as per ISO/IEC 17025-7.8.1.3. Such acertificate contains the calibration result, an
uncertainty, a description of the calibration procedureand the traceability. As an option, a certificate
including name and contact information of thecustomer may be ordered.
2 years
20 °C, normal incidence solar radiation, horizontal
mounting, irradiance level 1000 W/m2, heater andventilator [ON]based on experience the instrument sensitivity will notchange during storage. During use under exposure tosolar radiation the instrument “non-stability”
specification is applicable.
sensitivity adjustment and writing the calibration
history data via a PC using the Hukseflux Sensor
Manager software. Please refer to the Hukseflux
Sensor Manager manual for instructions.

Calibration method
Calibration uncertainty
Calibration certificate

Recommended recalibration interval
Reference conditions

Validity of calibration

Adjustment after re-calibration

DIGITAL COMMUNICATION
Digital output

SR30-M2-D1 manual v2304

irradiance in W/m²
instrument body temperature in °C
instrument internal humidity in %instrument internal pressure in Pa
instrument tilt angle in °ventilator speed in RPM
ventilator current in A
heater current in A

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Table 3.1.1 Specifications of SR30-M2-D1 (started on previous pages).
Hardware interface
Communication protocol
Transmission mode
BAUD rate settings
Data bits
Parity bits
Stop bits
Default serial settings
Default device address
RS-485 common mode range
INTERNAL PROTECTION MEASURESPower supply surge protection
Power supply TVS surge protection
standoff voltage(VDC[+] to VDC[-], Vs, max)
Power supply TVS surge protection peakpulse power capability
Power supply reverse polarity protection
RS-485 surge protection
RS-485 TVS surge protection standoff
voltage([data+]/[data-] to signal ground, Vcm,
max)
RS-485 TVS surge protection peak pulse
power capability
Pyranometer body DC isolation voltage(instrument body to signal ground, Viso)

2-wire (half-duplex)
RS-485
Modbus
RTU
9600, 19200, 38400, 115200
Eight
None, even, odd
One
19200 bits/s, eight data bits, even parity, one stop bit(19200 8E1)
1
± 12 VTVS diodes± 30 V

600 W
included
TVS diodes± 12 V

350 W
400 V

CABLE REQUIREMENTS
Recommended cable length
Maximum cable length
CABLE SPECIFICATIONS

≤5m
20 m

Standard cable length (see options)Standard cable conductors
Cable diameter
Cable connector
Connector protection class
Cable termination

5m
5 × 24 AWG
4.8 x 10-3 m
M12-A straight female connector, 5-pole
IP67removed sheath over 0.15 m; stranded copper
conductors with plastic insulators, stripped ends withferrulesreplacement cables with connector can be orderedseparately from Hukseflux

Cable replacement

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Table 3.1.1 Specifications of SR30-M2-D1 (started on previous pages).
OPTIONS
Longer cable: 10 or 20 metre length
Cable with M12-A female connector on
one end and stripped on other end(conductors stripped over 0.15 m withferrules)Cable with connector pair, 20 m length
Cable with male and female M12-A
connectors
calibration certificate including name andcontact information of the customer
ACCESSORIES

option code = total cable length

Levelling mount, for spring-loaded
levelling and mounting SR30 on asurfacemountable on flat surface
allowing tilt adjustment to 3.4 orequires 4 mm hex key or 10 mm spanner forconnecting to SR30
requires two M5 bolts and hex key for mounting to asurface (not included)
2 x M5 at 46 x 10-3 m centre to centre distance
option code = LM01
mountable on tubes Ø 25 to Ø 40 mm
one spring-loaded levelling mount, one clamp for tube
mounting and two sets of bolts (two M5x30 and two
M5x45) included
allowing tilt adjustment to 3.4 orequires 4 mm hex key for mounting and 4 mm hex
key or 10 mm spanner for connecting to SR30
option code = TLM01
PMF series mounting fixtures
Hukseflux Sensor Manager software, version v2021 orhigher. For the latest software and a dedicatedSensor Manager user manual, please checkhttps://www.hukseflux.com/downloads

Tube levelling mount, for spring-loaded
levelling and mounting SR30 on a tube

Other mounting options
Software for use with a PC

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option code = C07E-20 for 20 metres

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Dimensions of SR30-M2-D1

95

3.2

M5 (2x)

Ø 92

M6

105

46
Ø 68

Ø 25 - Ø 40 mm

Figure 3.2.1 Dimensions of SR30-M2-D1 in x 10-3 m. Mounts are optional.

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4 Standards and recommended practices foruse
Pyranometers are classified according to the ISO 9060 standard and the WMO-No. 8
Guide. Depending on the application, the instrument may be used in accordance with therecommended practices of ISO, IEC, WMO and / or ASTM.

4.1

Classification standards

Table 4.1.1 Standards for pyranometer classification. See the appendix for definitions ofpyranometer specifications, and a table listing the specification limits.
STANDARDS FOR INSTRUMENT CLASSIFICATIONISO STANDARD

EQUIVALENTASTM STANDARD

WMO

ISO 9060:2018
Solar energy -- specification andclassification of instruments formeasuring hemispherical solar anddirect solar radiation

Not available

WMO-No. 8; Guide toMeteorological Instruments
and Methods of Observation,
chapter 7, measurement ofradiation, 7.3 measurementof global and diffuse solar
radiation

4.2

General use for solar radiation measurement

Table 4.2.1 Standards with recommendations for instrument use in solar radiation
measurement.
STANDARDS FOR INSTRUMENT USE FOR HEMISPHERICAL SOLAR RADIATIONISO STANDARD

EQUIVALENTASTM STANDARD

WMO

ISO/TR 9901:2023
Solar energy -- pyranometers -Recommended practice for use

ASTM G183 - 15
Standard Practice for Field
Use of Pyranometers,
Pyrheliometers and UVRadiometers

WMO-No. 8; Guide toMeteorological Instruments
and Methods of Observation,
chapter 7, measurement ofradiation, 7.3 measurementof global and diffuse solar
radiation

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4.3

Specific use for outdoor PV system performance testing

Pyranometers are used for monitoring PV power plant efficiency, in order to measureincoming solar radiation independently from the PV system. Pyranometers can be placedin two positions:• Plane of Array (POA), parallel to the PV panels, for measurement of the in-plane
irradiance (also noted as Gi in IEC 61724-1)• horizontally, for measurement of the global horizontal irradiance (E, also noted as GHI
in IEC 61724-1)
SR30 also includes a tilt sensor. For PV systems with single-axis trackers, IEC 61724-1
Class A systems also require a tilt angle measurement.
The IEC suggested option to measure tilt by counting motor steps does not detect tracker
faults, which is one of its purposes. Also, counting steps will not lead to the required 1 ˚accuracy (Clause 10.1). Every SR30 tilt sensor is individually calibrated and temperaturecompensated between -30 and +50 ˚C, resulting in a high accuracy of < 1 ˚.
Table 4.3.1 Standards with recommendations for instrument use in PV system
performance testing.
STANDARDS ON PV SYSTEM PERFORMANCE TESTING
IEC / ISO STANDARD

EQUIVALENT ASTM STANDARD

IEC 61724-1; Photovoltaic system performancemonitoring – guidelines for measurement, dataexchange and analysis
SR30 complies, in its standard configuration,with the IEC 61724-1:2021 requirements ofClass A PV monitoring systems for solar
irradiance and tracker tilt angle measurements

ASTM E2848-13; Standard Test Method for
Reporting Photovoltaic Non-Concentrator
System Performance

COMMENT: IEC 61724-1 allows use ofpyranometers or reference cells according toIEC 60904-2 and -6. For IEC 61724-1,
pyranometer calibration uncertainty must be
better than 2 % (paragraph 8.2.2), tiltalignment within 1 ˚ tilt (paragraph 8.2.8).
Tracker tilt measurement shall be perfomedwith ± 1˚ accuracy.

COMMENT: confirms that a pyranometer is thepreferred instrument for outdoor PV testing.
Specifically recommends a “first class” (nowspectrally flat class B in ISO 9060:2018)
pyranometer (paragraph A 1.2.1.)

COMMENT: equals JISC 8906 (JapaneseIndustrial Standards Committee)

4.4

Specific use in meteorology and climatology

The World Meteorological Organization (WMO) is a specialised agency of the United
Nations. It is the UN system's authoritative voice on the state and behaviour of the

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earth's atmosphere and climate. WMO publishes WMO-No. 8; Guide to Meteorological
Instruments and Methods of Observation, in which a table is included on “level of
performance” of pyranometers. Nowadays, WMO conforms itself to the ISO classification
system.
In case there is no danger of deposition of dew and frost, the medium power mode
(using the ventilator but not the heater) offers the most accurate measurements overshort time intervals. Averages on the minute time scale produce the same result as in
the standard operating mode. The measurement is less sensitive to rapid changes of the
instrument temperature (thermal shock) resulting in less noise on the irradiance reading.

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4.5

General use for sunshine duration measurement

According to the World Meteorological Organization (WMO, 2003), sunshine duration
during a given period is defined as the sum of that sub-period for which the direct solar
irradiance exceeds 120 W/m2. WMO has approved the “pyranometric method” toestimate sunshine duration from pyranometer measurements (Guide to Meteorological
Instruments and Methods of Observation, Part I: Measurement of Meteorological
Variables; WMO-No.8; 2008; chapter 8). This implies that a pyranometer may be used,in combination with appropriate software, to estimate sunshine duration. Ask for ourapplication note.
Table 4.5.1 Standards with recommendations for instrument use in sunshine duration
measurement.
STANDARDS FOR INSTRUMENT USE FOR SUNSHINE DURATIONWMO
Guide to Meteorological Instruments and Methods of Observation, Part I: Measurement ofMeteorological Variables; WMO-No. 8; 2008; chapter 8, measurement of sunshine duration,section 8.2.2 Pyranometric Method

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5 Installation of SR30
5.1

Site selection and mechanical installation

Table 5.1.1 Recommendations for installation of pyranometers (continued on nextpage).
Location

the horizon should be as free from obstacles as
possible. Ideally, there should be no objects between
the course of the sun and the instrument.

Mechanical mounting / thermal insulationpreferably, use the optional spring-loaded levelling
mount for mounting to a flat surface, or use theoptional tube mount.
if not using the optional tube mount, use connection
by bolts to the bottom plate of the instrument. A
pyranometer is sensitive to thermal shocks, i.e. rapidchanges of the sensor body temperature. Do notmount the instrument with the body in direct thermal
contact to the mounting plate (so always use thelevelling feet also if the mounting is not horizontal),
do not mount the instrument on objects that become
very hot (black coated metal plates).

Instrument mounting with 2 bolts(without optional levelling mount)

2 x M5 bolt at 46 x 10-3 m centre to centre distanceon north-south axis, connection from below under thebottom plate of the instrument.

Instrument mounting with one bolt(without optional levelling mount)

1 x M6 bolt at the centre of the instrument,
connection from below under the bottom plate of the
instrument.

Performing a representative
measurement

the pyranometer measures the solar radiation in theplane of the sensor. Some measurements require thepyranometer to be installed in a tilted or inverted
position. The sensor bottom plate is parallel to theblack sensor surface and should be mounted parallelto the plane of interest.
In case a pyranometer is not mounted horizontally orin case the horizon is obstructed, therepresentativeness of the location becomes animportant element of the measurement. See thechapter on uncertainty evaluation.

Levellingin case of horizontal mounting, use the bubble level
and levelling feet.
after levelling horizontally (using the bubble level)
immediately store the tilt sensor output, and use thisvalue as the reference for monitoring both short-termand long-term changes.

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Table 5.1.1 Recommendations for installation of pyranometers (started on previous page).
Cable lengths

do not directly connect cables longer than 20 meters
to SR30. Whenever connection to a longer cable isrequired, connect the instrument to that cable througha suitable isolated interface (i.e. power and signal
isolation, e.g. through an isolated DC-DC converter
and an optically isolated RS-485 interface).

Cable ducts

use grounded metal cable ducts whenever possible,
however, do not run the cabling in a cable duct withhigh-power or noise emitting cabling. If possible, usea signal cable duct.

Electrical design, grounding of the bodyand cable shieldmechanical installation cannot be separated fromelectrical installation; pay special attention toelectrically grounding the body and cable shield of the
instrument, see next sections.

Tilted installationin most cases, for tilted installation, the tilt sensor
provides a sufficiently accurate measurement. The
register “tilt angle” can be used for verification of thetilt angle.

Instrument orientation

when installing in a horizontal orientation, byconvention: with the cable exit pointing to the nearest
pole, so the cable exit should point north in thenorthern hemisphere, south in the southernhemisphere.
when installing in a tilted orientation; keep theconnector pointing down to minimise humidity
ingress.

Installation height

SR30-M2-D1 manual v2304

in case of inverted installation, WMO recommends an
installation height above the surface between 1 and
2 m, reducing the effect of shadows and in order toobtain good spatial averaging (see also: Guide toInstruments and Methods of Observation: Volume I:
Measurement of Meteorological Variables; WMO No.8;
2018 edition; Section 7.3.3.4; p.266)

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5.2

Installation of the sun screen

The quick release system of SR30’s sun screen allows for easy and secure mounting andremoval of the sun screen on the sensor. SR30’s bubble level can be inspected at all
times, even with the sun screen installed: a small window allows to see the bubble level.
Installation and removal of the connector can be done after removal of the sun screen.
The quick release system consists of a spring loaded lever opposite the bubble level
window of the SR30 sun screen. The bottom of the handle can be pulled out gently. Oncethe handle is pulled out and fully released, as shown in the figure below, the sun screen
can be lifted off manually for removal. Installing the sun screen is easy too: pull out thebottom of the quick release system handle so it is fully released, place the screen on
SR30 and, once it is positioned properly, press the handle of the quick release system
until it is locked.

Figure 5.2.1 SR30’s sun screen with quick release system and bubble level window.

Figure 5.2.2 Installation of SR30’s sun screen

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5.3

Installation of optional mounts

5.3.1 Levelling mountThe optional levelling mount, for simplified mounting and levelling of SR30 on a flat surface
such as a platform or bracket, is easy to use. It can be fitted to SR30 using the mount’s
spring-loaded centre bolt and a 4 mm hex key or a 10 mm spanner. It can be mounted ona flat surface by inserting two M5 bolts (not included) in the designated holes.

Figure 5.3.1.1 Optional spring-loaded levelling mount for SR30.
The preferred way to connect the mount to SR30 and lock its connection, is by using a 4mm hex key via the bottom part of the levelling mount (see Figure 5.3.1.2). If thebottom part is not accessible, the connection between SR30 and the mount can be madeby using a 10 mm spanner (see Figure 5.3.1.3). The spanner may be used as well tolock, or unlock, when SR30 is already fitted to the mount (See Figure 5.3.1.4). In allcases, ensure the legs of SR30 fit into one of the small ledges of the levelling mount.
Locking is in place, when the nut of the spring-loaded centre bolt is turned all the way
towards SR30’s bottom panel.

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Figure 5.3.1.2 Bottom of SR30 levelling mount. Preferred (un)locking with 4 mm hex key.

Figure 5.3.1.3 SR30 levelling mount seen from above: (un)locking with a 10 mm spanner.

Figure 5.3.1.4 SR30 levelling mount seen from the side: (un)locking with a 10 mm spanner.

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The levelling mount is spring-loaded. Once SR30 is connected and locked to the levelling
mount, SR30 can be levelled by the user, judging the bubble level. Levelling is done byfastening or loosening SR30’s two adjustable levelling feet by hand. SR30’s static footremains fixed. Fasten or loosen both legs so that the instrument is level, judging by the
bubble level.

Figure 5.3.1.5 SR30 locked on its optional levelling mount: by fastening (on the left) or
loosening (on the right) SR30’s two adjustable feet, SR30 can be levelled, judging by the
bubble level. SR30’s static foot remains fixed. In all cases, ensure the legs of SR30 fit into oneof the small ledges of the levelling mount. Locking is in place, when the nut is turned all theway against the bottom plate of SR30.

5.3.2 Tube levelling mount
SR30 may also be mounted on a tube or a mounting rod using SR30’s optional tube mount.

Figure 5.3.2.1 SR30 mounted with its optional tube levelling mount on a tube.

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The tube mount option includes the levelling mount, described in the previous paragraph,a lower clamp for tube mounting and two sets of bolts for tube diameters 25 to 40 mm(tube not included). Installation requires a 4 mm hex key.

Figure 5.3.2.2 Optional tube levelling mount; installation requires a 4 mm hex key.

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5.4

Electrical installation

For reliable operation it is important to follow the installation instructions andrecommendation in this section carefully.
The wiring of SR30 is explained in Figures 5.4.1 and 5.4.2 and Table 5.4.1. On a coarse
level SR30 can be viewed as having three electrical ports: a DC power port, a signal port
and an enclosure port. The DC power port consists of the VDC [+] and VDC [-]connections used to power the instrument. The signal port consists of the RS-485[data+], [data-] and signal ground connections used for communication with the sensor.
The enclosure port consists of the sensor body and the cable shield connection. An
installation that is robust to electromagnetic interference aims to electrically isolate twoof these three ports. In addition, refer to the section “INTERNAL PROTECTION
MEASURES” in Table 3.1.1 for the maximum voltages between different parts of the
instrument as indicate in the diagram in Figure 5.4.1 and to Appendix 10.12 for a list of
all EMC testing performed.
A cable shield protects the conductors from electromagnetic interference and provides anelectrical connection to the instrument body. The instrument body is made of aluminium
and is electrically conducting. By mounting the instrument on a grounded conducting
platform, the instrument can be grounded. Since the shield is connected to the body, thisalso means that the shield is connected to the same ground. The instrument should
preferably be grounded at a single reference point. For more details please refer to thesections on “Internal protection” and “Electrical isolation, grounding and shieldconnection”.
Internally the instrument electronics are isolated from the body and the shield. To reduce
the effect of electrical interference on the sensor signal the electronics is capacitively
attached to the body. This capacitive coupling limits the maximum rated isolation voltage
between the electronics and the body, or, equivalently, between the cable shield and thepower supply and RS-485 wiring. The rated maximum isolation voltage is listed in the“Specifications” chapter.
The instrument must be powered by an external power supply that provides an operating
voltage in the specified range and that can source sufficient current to power the instrument.
To communicate with the instrument, the instrument must be connected to an RS-485
network. The connection consists of two differential signal wires (white and grey) and asignal ground wire (blue). See the “Connecting to an RS-485 network” section for moredetails on how to setup an RS-485 network.
NOTICE
This manual supports model SR30-M2-D1, the successor of SR30-D1.
Need support for the discontinued SR30-D1? Please refer to its separate manual.

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NOTICE
When SR30-D1 is installed using the recommended SR30-M2-D1 wiring scheme,
SR30-D1 RS-485 communication will NOT function reliably.
NOTICE
When SR30-M2-D1 is installed using the recommended SR30-D1 wiring scheme,
users will NOT benefit from improved signal integrity.

Figure 5.4.1 Electrical connections of SR30-M2-D1.
Table 5.4.1 Cable and connector connections of SR30-M2-D1.
PIN*

WIRE

SR30-M2-D1

1

Brown

VDC [+]

4Black

VDC [−]

3Blue

RS-485 signal ground

2

White

RS-485 [data+], B’ or B

5

Grey

RS-485 [data−], A’ or A-

Yellowcable shield / body*numbering as indicated in Figure 5.4.2
2
3

5

1

4

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Figure 5.4.2: Schematic of the M12-A connector layout of SR30-M2-D1, indicating the
PIN numbers.

5.5Internal protection

SR30 electronics are internally protected to improve reliability and reduce the risk ofdamage. See the Specifications chapter for the full list of protection levels. The following
protection measures are in place on the power supply wiring:• overvoltage protection• reverse polarity protection• surge protection (against voltage spikes)
and on the RS-485 signal wiring:• overvoltage protection• extended common mode range (Vcm, max, with respect to the RS-485 specification)• surge protection (against voltage spikes)
NOTICEThe RS-485 interface is not internally isolated from the power supply. Voltage
levels must not exceed the rated voltage to avoid damage.
Internally the instrument body is capacitively coupled to the instrument electronics to
reduce noise on the measurement signal. Please refer to the Specification chapter for the
maximum rated DC isolation voltage between the instrument body and the instrument
electronics (Viso).

5.6

Connecting to an RS-485 network

SR30 has an RS-485 hardware interface and uses the Modbus RTU protocol to handle thedata communication. The RS-485 standard, officially known as TIA/EIA-485, describes
the electrical interface (signal levels, timing, etc.) for a data communication system. Thissection explains how to integrate the SR30 in a RS-485 network, starting with a general
overview, followed by installation advice.

5.6.1 RS-485 network
SR30 is designed for use in a two-wire (half-duplex) RS-485 network. In such a network,
SR30 acts as a slave device, responding to data requests from the master device. An RS485 network (or bus), consists of a twisted wire pair for data transmission plus a signal
ground wire. The three channels are known as:• RS-485 [data+], B’ or B
• RS-485 [data-], A’ or A
• RS-485 signal ground

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RS-485 uses differential signalling for data transmission. This means that the logic states
are encoded in the electrical potential difference between the [data+] and [data-] lines,
whereas on a single-ended interface it would be encoded in the potential of the data linewith respect to the signal ground. When designed and installed correctly, RS-485
provides a robust reliable communication channel in electrically noisy environments.
An example of the topology of an RS-485 2-wire network is shown in Figure 5.6.1.1. The
network has a linear setup with side branches, called stub lines, to the connected devices(nodes) and line termination resistors at each end to reduce the effect of reflecting
signals.

Figure 5.6.1.1 Typical topology of a two-wire (half-duplex) RS-485 network. Figure
adapted from: Modbus over serial line specification and implementation guide v1.02(www.modbus.org). Neither the power supply nor any isolators that might be required areshown in this figure.
Line termination must be installed at both ends of the bus between the [data+] and[data-] lines. According to the RS-485 standard, termination resistors have a value of120 Ω and no more and no less than two line termination resistors should be installed ina single network. Failure to install line termination resistors may lead to signal reflections
which could compromise signal integrity. Placing more than two line termination resistorscauses excessive loads on the RS-485 bus which may compromise signal integrity andmay lead to damage to equipment.
NOTICELine termination is required at both ends of the bus between the [data+] and[data-] lines. Two, and no more and no less than two termination resistors

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should be placed (see also: MODBUS over serial line specification andimplementation guide v1.02, section 3.4.5, page 27).
To minimise noise on the network when no transmission is occurring, a so-called fail-safebiasing circuit can be installed. To do so, pull-up and pull-down resistors have to beinstalled on the [data+] and [data-] lines, respectively. For some devices the use of failsafe biasing is required for the devices to work. Typical values for both resistors are in
the range from 650 to 850 Ω. On the [data+] line this resistor is connected to a +5 VDC
supply and on the [data-] line to the signal ground. This will keep the data lines in a welldefined state when none of the connected devices is controlling the bus.
NOTICE
Fail-safe biasing (line polarization) may be required to minimize noise(see also: MODBUS over serial line specification and implementation guidev1.02, section 3.4.6, page 28).
Stub lines in the network should be avoided or kept as short as possible to avoid signal
reflection in these un-terminated line elements. The lower the BAUD rate of the serial
communication, the longer any stub lines can be without causing problems. Never use
stub lines longer than 20 metres.
NOTICEDo not use stub lines (derivations) longer than 20 metres (see also: MODBUS
over serial line specification and implementation guide v1.02, section 3.4.3,
page 27).

5.7

Electrical isolation, grounding and shield connection

Pyranometers are sensitive equipment. Electrical isolation and grounding need carefulconsideration when installing and operating SR30. The appropriate choice of electricalisolation and grounding of the pyranometer depends on the local situation. It is theusers’ responsibility to evaluate their situation and choose the best possible way of
isolating and grounding the instrument. Failure to do so may lead to damage toequipment or unreliable operation.
When designing the installation, the following should be taken into account:• SR30 has limited or no on-board electrical isolation between the instrument power
supply (DC power port), signal wiring (signal port) and body (enclosure port).
• the cable shield (yellow wire) is electrically connected to the SR30 body• the SR30 metal body is anodised. This forms a thin insulating encapsulation of themetal. As a consequence, the instrument may or may not become electrically.
connected to its mounting platform. Furthermore, corrosion, build-up of debris, etc.
may deteriorate the quality of the grounding connection over time. It is important toverify that the instrument is electrically connected to its mounting platform when the

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application requires this. The user must verify the state of the electrical connection
between the instrument and the mounting platform immediately after installation andlater on at regular intervals.
• the levelling mount and tube levelling mount are anodised. When mounting SR30 to amounting platform using the levelling or tube levelling mount, the instrument may or
may not become electrically connected to its mounting platform. The user must verify
the state of the electrical connection between the instrument and the mounting
platform through the levelling or tube levelling mount immediately after installationand later on at regular intervals.
WARNING
The SR30 instrument body, levelling mount and tube levelling mount are
anodised. When mounting SR30 to a mounting platform the instrument may or
may not become electrically connected to that mounting platform. The user mustverify the state of the electrical connection.

WARNING
Grounding or isolation of the instrument may deteriorate over time. Verify
grounding or isolation of the instrument according to the installation
requirements after installation and set up an inspection and maintenance planwith a regular inspection interval.

5.7.1 Spatially extended installations (total cable lengths >5 m)
To avoid exposure of the SR30 to large electrical currents or voltages caused by ground
potential differences, electrical isolation and grounding is an important point of attention
in the installation design. Since there is limited or no on-board electrical isolation
between the instrument power supply, signal wiring and body these can be considered tobe electrically connected for grounding purposes. The cable shield is connected to the
instrument body through the connector housing. In general, but in particular when SR30
is installed in a spatially extend network (distances between nodes greater than 5 m), it
is strongly recommended to use a single point of reference for grounding and otherwiring.
Whenever SR30 is installed in a spatially extended network, preferably the instrument
body is electrically connected to protective earth by bolting it to a grounded mounting
platform, while the instrument is powered from a suitable isolated power supply andconnected to the RS-485 network via a suitable optical isolator. The isolated power
supply and the optical isolator should be installed within 20 metres from the instrument.
In this case, the cable shield (yellow wire) should be left disconnected as it is connectedto the mounting platform via the sensor body. Do not directly connect cables longer than
20 metres to SR30. If longer cables are required, always electrically isolate the power
supply and RS-485 interface.

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NOTICE
Do not directly connect cables longer than 20 metres to SR30. If longer cables
are required always electrically isolate the instrument from that cable.
NOTICE
Ground potential differences may compromise reliable operation of the
instrument. Take special care of grounding and installation when installing SR30
in spatially extended networks.

5.7.2 Spatially compact installations (total cable lengths ≤5 m)
Preferably, the installation should be designed such that it is spatially compact (total
cable lengths/maximum distance between nodes less than 5 m) and the mounting
platform is directly connected to the pyranometer. In that case, it is recommended to
install the pyranometer, the power supply and the RS-485 interface on a single dedicatedmounting platform and use this platform to ground all components. Use cable ties or anelectrically conductive, grounded cable duct to fix the cable to the mast in order tominimize the impact of electromagnetic disturbances. An example is a point-to-point
network were a single SR30 is directly connected to a datalogger using the standard 5 m
cable supplied with the pyranometer, with no other nodes on the network.

5.8

Cabling requirements

Whenever using cables longer than 5 metres are used, e.g. 10 metres or 20 metrescables, an isolated interface (power and signal isolation) must be used at the end of thecable.
Do not directly connect cables longer than 20 metres to SR30. Whenever connection to alonger cable is required, connect the instrument to that cable through a suitable isolated
interface (i.e. power and signal isolation, e.g. through an isolated DC-DC converter andan optical isolator).
Preferably, use short cables with a length of 5 m or less. When extending cables isunavoidable the following must be considered:• The wire gauge (AWG) of the power wires, the corresponding electrical resistance of
those wires and the resulting voltage drop. If the voltage drop is too large proper
sensor operation may be impaired.
• The use of longer cables results in more pick-up and thus more noise on the RS-485
network, which can cause communication to fail. To reduce this effect, use wellshielded cables with twisted wire pairs.
• Ground potential differences must be considered. Refer to Section 5.7 for more
information on grounding.
• Cables must be suitable for outdoor use.

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5.9

A PC as RS-485 master

SR30 can be accessed and controlled using a Personal Computer (PC). In this case,communication with the sensor is most easily done through the user interface of the
Hukseflux Sensor Manager software. Alternatively, third-party software which supports
the Modbus RTU protocol can be used.
The easiest way to connect to the RS-485 interface is to use a USB-to-RS-485 converter.
On MS Windows these converters are usually auto-configured and a virtual serial port
becomes available on the system. This port can be used by the controlling software tocommunicate with the instrument. Two recommended RS-485 converter models to use
with SR30 are:• Advantech, Adam-4561, 1-port Isolated USB to RS-232/422/485 Converter• Moxa, UPort 1150I, 1-port RS-232/422/485 USB-to-serial converters with opticalisolation protection
NOTICE
When using the popular RS-485 converter solutions manufactured by the FTDI
company, e.g. model USB-RS485-WE-1800-BT using the FT232R chipset, pleaseuse so-called fail-safe biasing resistors as the idle state of these converters isundefined and is likely to cause communication problems.

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6 Communication with SR30
6.1

PC communication: Hukseflux Sensor Manager software

SR30 can be accessed via a PC. In that case, the communication with the sensor can bedone via the user interface offered by the Hukseflux Sensor Manager software or byanother Modbus testing tool.
The Hukseflux Sensor Manager software provides a user interface for communication
between a PC and SR30. It allows the user to locate, configure and test one or more
SR30’s and to perform simple laboratory measurements using a PC. The Hukseflux
Sensor Manager’s most common use is for initial functionality testing and modification of
the SR30 Modbus address and serial communication settings. It is not intended for longterm continuous data acquisition purposes.
The latest Hukseflux Sensor Manager software can be downloaded onwww.hukseflux.com/downloads. For support of the Sensor Manager software, please visit
the Sensor Manager’s online support page, which includes a dedicated user manual for
installing and using the software.
NOTICE
Always use the latest version of the Hukseflux Sensor Manager.

6.2

Network communication: getting started

Once the desired device address and serial communication settings have been set, SR30
can be connected to an RS-485 network and a power supply (see Chapter 5). Installing
an SR30 in an RS-485 network also requires configuring the Modbus communication forthis new Modbus RTU device. This usually consists of defining one or more requests thatcan be broadcast by the master. To read the irradiance the Modbus registers holding thetemperature compensated irradiance (register address 0x0002 and 0x0003) must be
read. See Table 6.2.1.
Table 6.2.1: Key registers for making a measurement.
MODBUS REGISTERSREGISTERADDRESS
2+3

PARAMETER
Irradiance(temperaturecompensated signal)

DESCRIPTION OF
CONTENT
Temperaturecompensated signal
in x 0.01 W/m²

ACCESSR

FORMAT OF
DATA
S32

For diagnostic purposes the Modbus registers containing the sensor body temperature,tilt angle, internal relative humidity, heater (electrical) current, ventilator (electrical)
current and ventilator speed can be read, see Table 6.2.2. For more details on how to
use these diagnostic values, please refer to Chapter 7.

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Table 6.2.2: Key registers for sensor diagnostics.
MODBUS REGISTERSREGISTERADDRESS
6

PARAMETERDESCRIPTION OF
CONTENTIn x 0.01 °C

ACCESSR

FORMAT OF
DATA
S16In x 0.01 %

R

U16

98

Sensor bodytemperature
Humidity

194

Tilt angle

In x 0.01 °

R

U16

196

Fan speed RPM

In x 1 RPM

R

U16

198

Heater current

In x 1 mA

R

U16

199

Fan current

In x 1 mA

R

U16

Typical operation requires the master to request the irradiance data in registers 0x0002
and 0x0003, sensor temperature in register 0x0006, and the sensor serial number inregister 0x0040 every 1 second, and store the 60 second averages. The data format ofregister 0x0002 and 0x0003 combined is a signed 32 bit integer and the temperature in
register 0x0006 is a signed 16 bit integer.
A maximum of five 16 bit Modbus registers may be read in a single request. In case six
or more registers are read in one request, SR30 will not respond. If the user needs thecontent of six or more registers, multiple request cycles must be performed.
A complete list of supported Modbus function codes and Modbus registers and coils canbe found in Appendix 10.12. For more information about the Modbus protocol pleaserefer to the “Modbus protocol specification” and “Modbus Serial Line Protocol and
Implementation Guide” available at www.modbus.org.
NOTICE
32 bit parameters located in two 16 bit Modbus registers must be read in asingle Modbus request to guarantee coherence of these two registers.
NOTICEThe sensor does not distinguish between input registers and holding registers,
nor does it distinguish between coils and discrete inputs.
NOTICE
Each device on the RS-485 network should have the same serial communication
settings.
NOTICE
Each Modbus device on the RS-485 network should have a unique device address.

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6.3

Changing the device address and serial communication
settings

Setting the device address and serial communication settings (BAUD rate and parity) canbe done in different ways:
by connecting the sensor to a PC and using the Hukseflux Sensor Manager;by connecting the sensor to a PC and using another Modbus testing tool. There arelinks to different solutions available at www.modbus.org;
by using the available network user interface software.

•••

To set the device address and serial communication settings using the Hukseflux Sensor
Manager, see the “Hukseflux Sensor Manager” manual.
The registers containing the device address and serial communication settings are listed
in Table 6.3.1. The serial communication settings are listed in Table 6.3.2.
The Modbus device address and serial settings can be manually changed at any time bywriting the new settings to the corresponding addresses. Valid device addresses are 1 to247. For the new settings to become effective the device needs to be restarted, either by
turning the power off and back on again or by performing a soft restart. A soft restartcan be initiated by writing the value 0xFF00 (decimal value 65280) to coil 0x0001(decimal value 0). Refer to the Appendix 10.11 for more information about writing
registers and coils and an overview of all registers and coils.

NOTICE
Each device on the RS-485 network should have the same serial communication
settings.
NOTICE
Each Modbus device on the RS-485 network should have a unique device address.

Table 6.3.1: Registers containing the device address and serial communication settings.
MODBUS REGISTERSREGISTERADDRESS
0

PARAMETER

1

Serialcommunication
settings

Device address

SR30-M2-D1 manual v2304

DESCRIPTION OF
CONTENT
Sensor address in
Modbus network,
default = 1
Sets the serial
communication,
see table 6.3.2,
default = 5

ACCESS
R/W

FORMAT OF
DATA
U16

R/W

U16

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Table 6.3.2: Specification of the serial communication settings in register 0x0001.
SERIAL COMMUNICATION SETTINGSSETTINGNUMBER
1

BAUD RATEDATABITSSTOPBITSPARITY

9600

8

1

none

2

9600

8

1

even

3

9600

8

1

odd

4

19200

8

1

none

5 ( = default)

19200

8

1

even

6

19200

8

1

odd

7

38400

8

1

none

8

38400

8

1

even

9

38400

8

1

odd

10

115200

8

1

none

11

115200

8

1

even

12

11520081odd

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7 Use of remote diagnostics
Remote monitoring of the sensor condition helps improve the accuracy and reliability ofthe measurement. It also allows to improve preventive maintenance and effective trouble
shooting. The following remote diagnostics signals are part of the digital output. It is up
to the user whether or not to use these diagnostics.
Chapter 6 contains details on the register structure, needed for reading the remotediagnostics output.

7.1

Recommendations

For remote diagnostics, we recommend to:• measure and store internal sensor humidity, ventilator speed, ventilator current,
heater current and tilt angle at 24:00 local time.
• monitor short term changes of the sensor tilt, and generate a warning in case ofchanges > 0.2 ° / min, after levelling horizontally (using the bubble level) or at a tilt
(using the tilt sensor), immediately store the tilt sensor output, and use this value as
the reference for monitoring both short-term and long-term changes.
• monitor long-term changes of the sensor tilt, and generate a warning in case ofchanges > 1 ° from the stored value.
• check the sensor temperature against the dewpoint or ambient temperature. The
sensor temperature should normally be higher than the ambient temperature anddewpoint. Whenever the sensor body temperature is below the dewpoint, water
condensation may form on the outside of the pyranometer, including the outer dome,
which can affect the irradiance measurement.
• monitor internal humidity trends on a yearly scale, using nighttime values only, andgenerate a warning if the relative humidity is consistently > 50 % at bodytemperatures < 20 °C.
• monitor ventilator speed and generate a warning if the speed is below 5000 RPM.
• monitor heater current and generate a warning if the current is below 1.0 A.

7.2

Sensor body temperature

SR30’s low temperature dependence and wide rated operating temperature range makes
it ideal for use under a broad range of temperatures from very cold to very hot
conditions. Measurement of the sensors’ temperature is done using a digital sensor
temperature sensor. The sensor signal serves to externally monitor the SR30
temperature and, at the same time, is used by the internal electronics for temperaturecorrection of the measurands. The temperature dependence of the irradiance signal of
every individual instrument is tested. Temperature correction of the irradiance signal isprogrammed into each sensor and is taken care of fully automatically by the internal
electronics. The remaining very small deviation from ideal behaviour is shown on the test
certificate. In combination with a dewpoint measurement, the temperature measurement
can also be used to check that the sensor remains above dewpoint. Whenever the sensor
body temperature is below the dewpoint, water condensation on the outside of the

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pyranometer should be expected and irradiance data may have to be discarded. When
operating SR30 in standard operating mode (heater [ON] and ventilator [ON]) thisshould not normally occur. When operating SR30 in low or medium power operating
mode, water condensation can occur.

7.3

Tilt angle

To allow remote monitoring of the instrument tilt and to assist in the tilted installation of
the instrument, the SR30 features a digital tilt sensor. The tilt sensor measures thegravitational acceleration on three axes and calculates the corresponding zenith tilt angleof the pyranometer. For an accurate, absolute measurement of the tilt angle with respect
to horizontal, the sensor is factory-calibrated relative to the bubble level and using an
independent tilt measurement. Temperature correction coefficients of the tilt
measurement are programmed during production and provided for each individual sensor
on the product certificate. The tilt sensor has an absolute accuracy of ± 1 ° between 0
and 90 ° tilt angle. This accuracy is sufficient for use in PV performance monitoring andinstallation in Plane of Array.

7.4

Internal relative humidity

When the SR30 accumulates too much moisture, the internals of the sensor will getdamaged. Therefore, it is advised to take regular measurements of the internal relative
humidity of the sensor. These measurements are made available in the “humidity”
register. We recommend taking regular measurements of the internal humidity of thesensor. The long-term (yearly) trend in relative humidity will show the slow saturation of
the internal desiccant. The desiccant replacement interval is < 5 years. The relative
humidity levels in the sensor depend both on the absolute temperature and the level ofsaturation of the desiccant and the type of desiccant. The desiccant releases absorbed
water as a function of temperature and saturation level. Because of these effects, theshort-term relative humidity measurement is not a good indicator of the desiccantcondition. The relative humidity levels are preferably measured at low temperatures; werecommend to store measurements taken around midnight (24:00 local time) andmonitor changes on a yearly basis. The combined accuracy of the relative humidity
sensor is approximately 5 % of the reading.

7.5

Heater current

The heater current measurement is an indicative, unverified measurement. Using theheater current reading, an estimation of the heater power can be made. Because thevoltage across the heating element is 5.0 Volt, the heater power is given by:
Pheater [W] = 5.0 [V] x “heater current” [A]Please note that even though the power delivered by the heater is the largest
contributor, dissipation by the ventilator and the electronic circuitry also contribute toheating of the sensor.

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7.6

Ventilator current

The rotation speed of the ventilator can vary significantly with temperature. Thisvariation will also be reflected in the ventilator current. Apart from this, the ventilator
current measurement is an unverified measurement. For these reasons the ventilator
current reading should only be used as a binary [ON]/[OFF] indicator, solely to determine
the actual ventilator state independently.

7.7

Ventilator speed

The fan speed gives the actual rotation frequency of the fan in RPM (revolutions per
minute), irrespective of whether it is switched on or off. The nominal ventilator speed is
7400 RPM at 20 °C. Depending on operating conditions the speed may vary. Especially attemperatures below -10 °C ventilator speed may be significantly lower. When the speed
consistently falls below 5000 RPM, maintenance is required, and replacement of theventilator may be needed. The ventilator replacement interval is < 5 years.

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8 Making a dependable measurement
8.1

The concept of dependability

A measurement with a pyranometer is called “dependable” if it is reliable, i.e. measuring
within required uncertainty limits, for most of the time and if problems, once they occur,can be solved quickly.
The requirements for a measurement with a pyranometer may be expressed by the user
as:
•
•
•

required uncertainty of the measurement (see following paragraphs)
requirements for maintenance and repairs (possibilities for maintenance and repair
including effort to be made and processing time)a requirement to the expected instrument lifetime (until it is no longer feasible torepair)

It is important to realise that the uncertainty of the measurement is not only determinedby the instrument, but also by the way it is used.
In case of pyranometers, the measurement uncertainty as obtained during outdoor
measurements is a function of:
•
•
•
•
•
•

the instrument classthe calibration procedure / uncertainty
the duration of instrument employment under natural sunlight (involving the
instrument stability specification)
the measurement conditions (such as tilting, ventilation, shading, instrument
temperature)
maintenance (mainly fouling)
the environmental conditions*

Therefore, ISO 9060 says, “statements about the overall measurement uncertainty under
outdoor conditions can only be made on an individual basis, taking all these factors into
account”.
* defined by Hukseflux as all factors outside the instrument that are relevant to themeasurement such as the cloud cover (presence or absence of direct radiation), sunposition, the local horizon (which may be obstructed) or condition of the ground (whentilted). The environmental conditions also involve the question whether or not themeasurement at the location of measurement is representative of the quantity thatshould be measured.

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8.2

Reliability of the measurement

A measurement is reliable if it measures within required uncertainty limits for most of thetime. We distinguish between two causes of unreliability of the measurement:••

related to the reliability of the pyranometer and its design, manufacturing, calibration(hardware reliability).
related to the reliability of the measurement uncertainty (measurement reliability),
which involves hardware reliability as well as condition of use.

Most of the hardware reliability is the responsibility of the instrument manufacturer.
The reliability of the measurement however is a joint responsibility of instrument
manufacturer and user. As a function of user requirements, taking into accountmeasurement conditions and environmental conditions, the user will select an instrumentof a certain class, and define maintenance support procedures.
In many situations there is a limit to a realistically attainable accuracy level. This is due
to conditions that are beyond control once the measurement system is in place. Typicallimiting conditions are:•••the measurement conditions, for instance when working at extreme temperatures
when the instrument temperature is at the extreme limits of the rated temperature
range.
the environmental conditions, for instance when installed at a sub-optimalmeasurement location with obstacles in the path of the sun.
other environmental conditions, for instance when assessing PV system performanceand the system contains panels at different tilt angles, the pyranometermeasurement may not be representative of irradiance received by the entire PV
system.

The measurement reliability can be improved by maintenance support. Important aspects
are:
•

•

dome fouling by deposition of dust, dew, rain or snow. Fouling results in undefinedmeasurement uncertainty (sensitivity and directional error are no longer defined).
This should be solved by regular inspection and cleaning.
sensor instability. Maximum expected sensor aging is specified per instrument as its
non-stability in [% change / year]. In case the sensor is not recalibrated, theuncertainty of the sensitivity gradually will increase. This is solved by regular
recalibration.

Another way to improve measurement reliability is to introduce redundant sensors.
••

the use of redundant instruments allows remote checks of one instrument using theother as a reference, which leads to a higher measurement reliability.
in PV system performance monitoring, in addition to instruments measuring in thePlane of Array, horizontally placed instruments are used for the measurement of
global radiation. Global irradiance data enable the user to compare the local climate

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and system efficiency between different sites. These data can also be compared tomeasurements by local meteorological stations.

8.3

Repair and maintenance

Dependability is not only a matter of reliability, but also involves the reaction to
problems; if the processing time of service and repairs is short, this contributes to thedependability.
The main maintenance actions are:••••cleaning of dome
replacement of desiccant
replacement of cabling
replacement of ventilator

For optimisation of dependability a user should:••

design a schedule of regular maintenancedesign a schedule of repair or replacement in case of defects

When operating multiple instruments in a network, Hukseflux recommends keeping
procedures simple and having a few spare instruments to act as replacements duringservice, recalibrations and repair.

8.4

Uncertainty evaluation

The uncertainty of a measurement under outdoor or indoor conditions depends on manyfactors, see paragraph 1 of this chapter. It is not possible to give one figure forpyranometer measurement uncertainty. The work on uncertainty evaluation is acontinuous effort. There are several groups around the world participating instandardisation of the method of calculation. The consensus is that measurement
uncertainty should be evaluated according to the “Guide to Expression of Uncertainty in
Measurement” or GUM).

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8.4.1 Evaluation of measurement uncertainty under outdoor conditions
Hukseflux actively participates in the discussions about pyranometer measurement
uncertainty; we also provide spreadsheets, reflecting the latest state of the art, to assist
our users in making their own evaluation. The input to the assessment is summarised:
1) The formal evaluation of uncertainty should be performed in accordance with ISO 98-3
Guide to the Expression of Uncertainty in Measurement, GUM.
2) The specifications of the instrument, acceptance interval plus guard band, according to
the list of ISO 9060 classification of pyranometers and pyrheliometers are entered aslimiting values of possible errors, to be analysed as type B evaluation of standard
uncertainty per paragraph 4.3.7. of GUM. A priori distributions are chosen as rectangular.
3) A separate estimate has to be entered to allow for estimated uncertainty due to the
instrument maintenance level.
4) The calibration uncertainty has to be entered. Please note that Hukseflux calibration
uncertainties are lower than those of alternative equipment. These uncertainties areentered in measurement equation (equation is usually Formula 0.1: E = U/S), either as
an uncertainty in E (zero offsets, directional response) in U (voltage readout errors) orin S (tilt error, temperature dependence, calibration uncertainty).
5) In uncertainty analysis for pyranometers, the location and date of interest is entered.
The course of the sun is then calculated, and the direct and diffuse components are
estimated, based on a model; the angle of incidence of direct radiation is a major factor
in the uncertainty.
6) In uncertainty analysis for modern pyrheliometers: tilt angle dependence often is so
low that one single typical observation may be sufficient.
7) In case of special measurement conditions, typical specification values are chosen.
These should for instance account for the measurement conditions (shaded / unshaded,ventilated/ unventilated, horizontal / tilted) and environmental conditions (clear sky /cloudy, working temperature range).
8) Among the various sources of uncertainty, some are “correlated”; i.e. present during
the entire measurement process, and not cancelling or converging to zero when
averaged over time; the off-diagonal elements of the covariance matrix are not zero.
Paragraph 5.2 of GUM.
9) Among the various sources of uncertainty, some are “uncorrelated”; cancelling or
converging to zero when averaged over time; the off-diagonal elements of the covariancematrix are zero. Paragraph 5.1 of GUM.
10) Among the various sources of uncertainty, some are “not included in analysis”; thisapplies for instance to non-linearity for pyranometers, because it is already included in
the directional error, and to the tilt response for pyranometers when measuring global
horizontal irradiance.

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Table 8.4.1.1 Estimates of achievable uncertainties of measurements withpyranometers. The estimates are based on the ISO 9060:2018 specification limits,(tolerance intervals including guard bands) and a calibration uncertainty of 1.5 %, forsunny, clear sky days and well maintained stations, without uncertainty loss due to lackof maintenance and due to instrument fouling. The table specifies expanded uncertainties
with a coverage factor of 2 and confidence level of 95 %. Estimates are based on 1 s
sampling. IMPORTANT NOTE: there is no international consensus on uncertainty
evaluation of pyranometer measurements, so this table should not be used as a formalreference.
Pyranometer
class(ISO 9060)
spectrally flat
Class A (SR30)

spectrally flat
Class Aseasonlatitudeuncertainty
minute totals
at solar noon

uncertainty
hourly totals
at solar noon

uncertainty
daily totals

mid-latitude

1.8 %

1.8 %

2.3 %

summerequator

1.8 %

1.8 %

2.3 %

winterpole
mid-latitude

2.5 %
3.5 %

2.5 %
3.6 %

3.3 %
5.1 %

mid-latitude

3.0 %

3.1 %

3.9 %

equator

3.1 %

3.1 %

3.8 %

pole

4.0 %

4.0 %

5.2 %

mid-latitude

5.5 %

5.5 %

8.1 %

mid-latitude

5.3 %

5.4 %

6.9 %

equator

5.4 %

5.4 %

6.7 %

pole

7.1%

7.1 %

9.2 %

mid-latitude

9.7 %

9.9 %

14.6 %

mid-latitude

11.7 %

11.8 %

14.1 %

equator11.8 %

11.8 %

13.7 %

pole

13.8 %

13.8 %

16.7 %

mid-latitude

17.4 %

17.6 %

25.1 %

summerwinterspectrally flat
Class Bsummerwinterspectrally flat
Class C

summerwinter

8.4.2 Calibration uncertainty
New calibration procedures were developed in close cooperation with PMOD World
Radiation Center in Davos, Switzerland. The latest calibration method results in an
uncertainty of the sensitivity of less than 1.2 %, compared to typical uncertainties ofhigher than 1.7 % for this pyranometer class. See the appendix for detailed information
on calibration hierarchy.

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9 Maintenance and trouble shooting
9.1

Recommended maintenance and quality assurance

SR30 can measure reliably at a low level of maintenance in most locations. Usuallyunreliable measurements will be detected as unreasonably large or small measured
values. As a general rule this means that regular visual inspection combined with acritical review of the measured data, preferably checking against other measurements, isthe preferred way to attain a reliable measurement.
The IEC 61724-1 standard covering PV system performance monitoring and the WMO
manual covering meteorological network operation, have stricter requirements thanthose in table 9.1.1. IEC recommends weekly cleaning and inspection for its Class A
systems, and yearly pyranometer re-calibration. WMO recommends daily inspection andcleaning of pyranometers used in meteorological networks.
Table 9.1.1 Recommended maintenance of SR30. If possible, the data analysis andcleaning (1 and 2) should be done on a daily basis. (continued on next page)
MINIMUM RECOMMENDED PYRANOMETER MAINTENANCE
INTERVALSUBJECTACTION1

1 weekdata analysis

compare measured data to maximum possible / maximum
expected irradiance and to other measurements nearby(redundant instruments). Also historical seasonal records canbe used as a source for expected values. Analyse nighttime
signals. These signals may be negative (down to - 5 W/m2 on
clear windless nights), due to zero offset a. In case of use with
PV systems, compare daytime measurements to PV system
output. Look for any patterns and events that deviate fromwhat is normal or expected.
check tilt, internal humidity, internal pressure, ventilator speed
and heater current according to the recommendations in thechapter about remote diagnostics

2

2 weeks

cleaning

use a soft cloth to clean the dome of the instrument,
persistent stains can be treated with soapy water or alcohol3

6 months

inspection

inspect cable quality, inspect connectors, inspect mounting
position, inspect cable, clean instrument, clean cable, inspectlevelling, change instrument tilt angle in case this is out ofspecification, inspect mounting connection electrically (forisolation or conduction), inspect interior of dome forcondensation

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MINIMUM RECOMMENDED PYRANOMETER MAINTENANCE (continued)

5

INTERVALSUBJECTACTION

2 years

recalibration

recalibration by side-by-side comparison to a higher standard
instrument in the field according to ISO 9847. For sensitivity
adjustment and writing the calibration history data via a PC
using the Hukseflux Sensor Manager software, please refer tothe Hukseflux Sensor Manager manual for instructions.
Typically during calibration desiccant is replaced. Ask the
manufacturer for directions.

lifetime
assessment

judge if the instrument should be reliable for another 2 years,
or if it should be replaced

67< 5 years

desiccantreplacement

When necessary have desiccant replaced (see also section
7.4). Contact manufacturer for servicing options.

8< 5 years

ventilator
replacement

When necessary have ventilator replaced (see also sections
7.6 and 7.7). Contact manufacturer for servicing options

parts
replacement

if applicable / necessary, replace the parts that are most
exposed to ageing and weathering; cable, connector, sunscreen.
NOTE: use Hukseflux approved parts only.

9

9.2

Trouble shooting

Table 9.2.1 Trouble shooting for SR30 (continued on next pages)
GeneralInspect the instrument for any damage.
Inspect if the connector is properly attached.
Check the condition of the connectors (on chassis as well as the cable).
Inspect if the sensor receives DC voltage power in the working range.
Inspect the connection of the shield.
Inspect the connection of the sensor power supply.
Inspect the connection of the RS-485 signal ground to the RS-485 interface.
Read out the internal humidity Modbus register. If the reading is > 50 % at 20 °C
for at least 24 hours, the sensor may be leaking, or the desiccant may besaturated. If internal humidity is stored, look at the long-term trend. To
investigate leakage, the user may also read out the internal pressure sensor andsee if the internal pressure correlates (the pressure divided by the temperature
should be approximately constant) with body temperature. This is a sign that theconstruction is closed, not leaking.
Please contact the factory to discuss diagnostics and possible action.

Prepare forindoor testing

Install the Sensor Manager software on a PC. Equip the PC with RS-485
communication. Put DC voltage power to the sensor and establish communication
with the sensor. At power–up the signal may have a temporary output level
different from zero; an offset. Let this offset settle down.

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Not able tocommunicate
with thesensorCheck all physical connections to the sensor and try connecting to the sensor
again.
Check the cable for broken/damaged wires by measuring the electrical resistancefrom pins to cable ends. The electrical resistance should be < 10 Ω. In case of
doubt, try a new cable.
Make sure that all device addresses on the bus are unique.
Check if the correct device address and serial communication settings are being
used. Default settings upon delivery are listed in section 3.1. If settings are notknown use the Hukseflux Sensor Manager. Connect sensor to a PC and perform asearch operation with the Sensor Manager to determine the pyranometer’s device
address and serial communication settings. Note that this may take up to 30
minutes, depending on the search range. If all physical connections are correct,
and communication with the sensor still cannot be established, please contact thefactory to send the sensor to the manufacturer for diagnosis and service.

Does notrespond to arequest for 6
or moreregisters

It is not possible to request more than five 16 bit registers in one request. In caseof requesting six or more registers in just one request, the sensor will not
respond. If six or more registers are to be read, use multiple requests: the sensor
will respond as expected.

The irradiancesignal isunrealisticallyhigh or low

Note that night-time signals may be negative (down to -5 W/m2 on clear windlessnights in standard operating mode), due to zero offset a.
Check if the pyranometer has clean domes.
Check the location of the pyranometer; are there any obstructions that could
explain the measurement result.
Check the orientation / levelling of the pyranometer.
Check if the irradiance signal responds to light: expose the sensor to a strong lightsource, for instance a 100 W light bulb at 0.1 m distance. The signal should read
> 100 W/m2 now. Darken the sensor either by putting something over it orswitching off the light. The instrument voltage output should go down and within
one minute approach 0 W/m2.
Check if the sensitivity programmed into the pyranometer corresponds to thesensitivity on the calibration certificate.
Check if the correct Modbus registers are being read (see section 6.2).
Check if the correct multiplication factor is used in the data processing (irradianceregisters are in 0.01 W/m2).
Check that the most-significant word (MSW) and least-significant word (LSW) of
the irradiance registers are being read in a single Modbus request.
Check the data acquisition by replacing the sensor with a spare sensor with thesame Modbus device address.

The sensor
signal shows
unexpectedvariations

Check the presence of strong sources of electromagnetic radiation (radar, radio).
Check the condition and connection of the shield.
Check the condition of the sensor cable.
Check if the cable is not moving during the measurement.
Check the condition of the connectors (on chassis as well as the cable)

The outerdome showsinternal
condensation

In case there is a minor layer of moisture that is hardly visible: replace thedesiccant and wait a few days to see if the situation improves. Ask the
manufacturer for instructions.

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The innerdome showsinternal
condensation

9.3

Arrange to send the sensor to the manufacturer for diagnosis and service.

Calibration and checks in the field

Recalibration of field pyranometers is typically done by comparison in the field to areference pyranometer. The applicable standard is ISO 9847 “International StandardSolar Energy- calibration of pyranometers by comparison to a reference pyranometer”. At
Hukseflux, an indoor calibration according to the same standard is used.
Hukseflux’ recommendation for re-calibration: if possible, perform calibration indoor bycomparison to an identical reference instrument, under normal incidence conditions.
The accuracy for indoor calibration generally is acceptable for solar energy performancemonitoring, while outdoor calibration in general is not sufficient for that. See ourapplication note why indoor calibration is preferable.
The recommended calibration interval of pyranometers is 2 years. The registers
containing the applied sensitivity and the calibration history of SR30 are accessible forusers. This allows the user to choose his own local calibration service. The same feature
may be used for remotely controlled re-calibration of pyranometers in the field. Ask
Hukseflux for information on ISO and ASTM standardised procedures for field calibration.
For sensitivity adjustment and writing the calibration history data via a PC using the
Hukseflux Sensor Manager software, please refer to the Hukseflux Sensor Manager
manual for instructions.
In case of field comparison; ISO 9847 recommends field calibration to a higher classpyranometer (7.2). Hukseflux suggests to use sensors of the same model and class,because intercomparisons of similar instruments have the advantage that they sufferfrom the same offsets. It is therefore just as good to compare to pyranometers of thesame brand and type as to compare to an instrument of a higher class. ISO requires toperform field calibration during several days; at least 2 days under cloudless conditions.
ISO 9847 sets strict requirements for datasets (solar position), data rejection, outlier
rejection, and statistical analysisd data analysis. Every outdoor must have an individual
uncertainty evaluation, which includes the standard deviation of the data.
Hukseflux’ main recommendations for field intercomparisons are:1) to take normal incidence as a reference and not the entire day, working at zenith
angles < 40 ˚ and irradiance levels > 700 W/m2..
2) to take a reference of the same brand and type as the field pyranometer or apyranometer of a higher class, and
3) to connect both to the same electronics, so that electronics errors (also offsets) areeliminated.
4) to mount all instruments on the same platform, so that they have the same bodytemperature.

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5) to analyse radiation values at normal incidence radiation (possibly tilting theradiometers to approximately normal incidence), if this is not possible to compare 1 hour
totals around solar noon for horizontally mounted instruments.
6) for spectrally flat Class C radiometers, to correct deviations of more than ± 10 %.
Lower deviations should be interpreted as acceptable and should not lead to a revised
sensitivity.
7) for spectrally flat Class B pyranometers, to correct deviations of more than ± 5 %.
Lower deviations should be interpreted as acceptable and should not lead to a revised
sensitivity.
8) for spectrally flat Class A instruments, to correct deviations of more than ± 3 %.
Lower deviations should be interpreted as acceptable and should not lead to a revised
sensitivity.

9.4

Data quality assurance

Quality assurance can be done by:•••analysing trends in solar irradiance signal
plotting the measured irradiance against mathematically generated expected values
comparing irradiance measurements between sites•

monitoring statistics on the data communication quality, e.g. the number of failed
communication events (Modbus CRC fails) per unit time

The main idea is that one should look out for any unrealistic values. There are programson the market that can semi-automatically perform data screening.

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10 Appendices10.1 Appendix on tools for SR30-M2-D1
Table 10.1.1 Specifications of tools for SR30-M2-D1.

Tooling required for opening of the sensor bottom

T10 torx key

Tooling required for mounting and levelling SR30
with the optional (tube) levelling mount

4 mm hex key
and (alternatively) 10 mm spanner

10.2 Appendix on spare parts for SR30-M2-D1
•
•
•
•
•
•
•
•
•
•

levelling feet (set of 2)
static footsun screen for SR30. Specify SCR05.
cable for SR30, with female M12-A connector at sensor end, conductors stripped over
0.15 m with ferrules (5, 10, 20 m). Specify cable length
cable for SR30, 20 m length, with male and female M12-A connectors(order number C07E-20)
levelling mount for SR30, for spring-loaded levelling and mounting SR30 on a surface(order number LM01)
tube levelling mount for SR30, for spring-loaded levelling and mounting SR30 on a
tube (order number TLM01)
lower clamp for tube mountpair of M5x30 bolts for tube mountpair of M5x45 bolts for tube mount

NOTE: Outer dome, bubble level, thermopile sensor and internal sensors of SR30 cannot
be supplied as spare parts. In case of damage to the SR30, after repair the instrument
must be tested to verify performance within specification limits. This is required by ISO
9060. Testing involves verification of the directional response after dome, printed circuitboard and thermal sensor replacement; verification of the temperature response afterthermal sensor and internal sensors replacement and tilt sensor calibration after internalsensors replacement.

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10.3 Appendix on the ventilator
The nominal ventilator speed is 7400 RPM at 20 °C. Depending on operating conditions
the speed may vary. The normal startup time is less than 10 seconds. At temperatures
below -10 °C the startup time may increase to several minutes and the ventilator speed
may drop. The slow startup does not affect the lifetime of the ventilator. Variations of the
fan speed do not affect the instrument performance. The ventilator life expectancy L10% is
70,000 hours and the MTBF (Mean Time Between Failure) is 350,000 hours whencontinuously operated at 40 °C. Therefore a lifetime < 5 years is specified for theventilator under typical operating conditions.
The recommended operation is either continuously [ON] or continuously [OFF]. Switching[ON] and [OFF] frequently (for example daily) reduces the ventilator lifetime. In case theventilator speed is < 5000 RPM at 20 °C consistently, there may be a problem and fan
replacement may be needed. Factors that may negatively impact the fan lifetime are:• long operation at elevated temperatures, especially above +70 °C• frequently (re-)starting the ventilator• excessive mechanical shocks and vibrations

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10.4 Appendix on standards for classification and calibration
Both ISO and ASTM have standards on instrument classification and methods ofcalibration. The World Meteorological Organisation (WMO) has largely adopted the ISOclassification system.
Table 10.4.1 Pyranometer standardisation in ISO and ASTM.
STANDARDS ON INSTRUMENT CLASSIFICATION AND CALIBRATIONISO STANDARD

EQUIVALENT ASTM STANDARD

ISO 9060:2018 Solar energy -- Specificationand classification of instruments for measuring
hemispherical solar and direct solar radiation

not available
Comment: work is in progress on a new ASTM
equivalent standard

ISO 9846:1993 Solar energy -- Calibration ofa pyranometer using a pyrheliometer

ASTM G167 - 15 Standard Test Method for
Calibration of a Pyranometer Using a
PyrheliometerISO 9847:2023 Solar energy -- Calibration ofpyranometers by comparison to a reference
pyranometer

ASTM E824 -10 Standard Test Method forTransfer of Calibration from Reference to Field
Radiometers
ASTM G207 - 11 Standard Test Method for
Indoor Transfer of Calibration from Reference toField Pyranometers

ISO 9059:1990 Solar energy -- Calibration offield pyrheliometers by comparison to areference pyrheliometer

ASTM E816-15 Standard Test Method for
Calibration of Pyrheliometers by Comparison toReference Pyrheliometers10.5 Appendix on calibration hierarchy
Traceability of pyranometer and pyrheliometer sensitivities is to SI via the WorldRadiometric Reference, WRR. WRR is a “consensus standard”.
The distinguishing feature of traceability to WRR is that reference-operating conditions
include the spectrum of natural direct solar radiation (source ISO 9847:2023).
WRR is maintained by the World Radiation Center in Davos Switzerland (PMOD /WRC),using a group if instruments called the World Standard Group (WSG). PMOD/WRC is a
designated institute of the Swiss Federal Office of Metrology, the Swiss signatory of the
CIPM Mutual Recognition Agreement (MRA). PMOD/WRC has an MRA with WMO as well.
Use of WRR is mandatory when working according to the standards of both WMO andISO. ISO 9874 states under paragraph 1.3: the methods of calibration specified are

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traceable to the WRR. The WMO manual states under paragraph 7.1.2.2: the WRR is
accepted as representing the physical units of total irradiance.

See www.pmodwrc.ch

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The Hukseflux standard is traceable to an outdoor WRR calibration. Some small
corrections are made to transfer this calibration to the Hukseflux standard conditions:sun at zenith and 1000 W/m2 irradiance level. During the outdoor calibration the sun istypically at 20 to 40 ° zenith angle, and the total irradiance at a 700 W/m2 level.
Table 10.5.1 Calibration hierarchy for pyranometers.
WORKING STANDARD CALIBRATION AT PMOD / WRC DAVOS

Calibration of working standard pyranometers:
Method: outdoor calibration using the “continuous sun-and-shade method. This working
standard has an uncertainty “uncertainty of standard”. The working standard has beencalibrated under certain “test conditions of the standard”. The working standard has
traceability to WRR world radiometric reference.
CORRECTION OF (WORKING) STANDARD CALIBRATION TO STANDARDISEDREFERENCE CONDITIONSCorrection from “test conditions of the standard” to “reference conditions” i.e. to 20 °C, normal
incidence, horizontal mounting and an irradiance level of 1000 W/m²:
Using known working standard pyranometer properties: temperature response, directional
response, non-linearity, tilt response).
INDOOR PRODUCT CALIBRATION

Calibration of products, i.e. pyranometers:
Method: according to ISO 9847, Type A1, which is an indoor calibration.
This calibration has an uncertainty associated with the method.
CALIBRATION UNCERTAINTY CALCULATION

ISO 98-3 Guide to the Expression of Uncertainty in Measurement, GUM Determination of
combined expanded uncertainty of calibration of the product, including uncertainty of theworking standard, uncertainty of correction, uncertainty of the method (transfer error). The
coverage factor must be determined; at Hukseflux we work with a coverage factor k = 2.

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10.6 Appendix on meteorological radiation quantities
A pyranometer measures irradiance. The time integrated total is called radiant exposure.
In solar energy radiant exposure is often given in W∙h/m2.
Table 10.6.1 Meteorological radiation quantities as recommended by WMO (additional
symbols by Hukseflux Thermal Sensor). POA stands for Plane of Array irradiance. The
term originates from ASTM and IEC standards.
SYMBOLDESCRIPTIONCALCULATION

UNITS

E↓

downward irradianceE↓ = Eg ↓ + El↓

W/m2

H↓

downward radiant exposure
for a specified time intervalH↓ = Hg↓ + Hl ↓

J/m2

E↑

upward irradianceE↑ = Eg ↑ + El ↑

W/m2

H↑

upward radiant exposure
for a specified time interval
direct solar irradiancenormal to the apparent
solar zenith angle
solar constantH↑ = Hg↑ + Hl ↑J/m2

W∙h/m2

W/m2

DNI

global irradiance;
hemispherical irradiance ona specified, in this casehorizontal surface.*
global irradiance;
hemispherical irradiance ona specified, in this casetilted surface.*
downward diffuse solar
radiation

Eg↓ = E cos θh + Ed↓

W/m2

GHI

GlobalHorizontal
Irradiance

Eg ↓ = E∙cos θt +Ed ↓ t + Er↑ t ***

W/m2

POA

Plane of
Array

W/m2

DHI

DiffuseHorizontal
IrradianceE

E0
Eg ↓ hEg ↓ tEd ↓El ↑, El ↓Er↑

upward / downward longwave irradiancereflected solar irradianceE*

net irradianceT↓apparent surface
temperature**apparent sky
temperature**
sunshine duration

T↑
SD

ALTERNATIVE
EXPRESSION

Change ofunits
DirectNormalIrradiance

W/m2

W/m2
W/m2
E* = E↓ – E↑

W/m2
ºC or KºC or Kh

θ is the apparent solar zenith angle θh relative to horizontal, θt relative to a tilted surfaceg = global, l = long wave, t = tilted *, h = horizontal**
distinction horizontal and tilted from Hukseflux,**
T symbols introduced by Hukseflux,***
contributions of Ed ↓ t and Er↑ t are Ed ↓ and Er↑ both corrected for the tilt angle of the surface

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10.7 Appendix on ISO and WMO classification tables
Table 10.7.1 Valid classification table for pyranometers per ISO 9060:2018 and WMO.
NOTE: WMO specification of spectral selectivity is different from that of ISO. Hukseflux
conforms to the ISO limits. WMO also specifies expected accuracies. ISO finds this not to
be a part of the classification system because it also involves calibration. Please note that
WMO achievable accuracies are for clear days at mid latitudes and that the uncertainty
estimate does not include uncertainty due to calibration*. Continued on next page.
ISO 9060:2018 CLASSIFICATION** TABLE
ISO ACCURACY CLASSSpecification
acceptance interval (guard band)
Response time (95 %)Zero offset a (response to 200 W/m2 net
thermal radiation)
Zero offset b (response to 5 K/h in ambient
temperature)
Total zero offset

CLASS A

CLASS B

CLASS C

10 s (1 s)± 7 W/m2(2 W/m2)± 2 W/m2(0.5 W/m2)± 10 W/m2(2 W/m2)± 0.8 %
(0.2 %)± 0.5 %
(0.2 %)± 10 W/m2

20 s (1s)± 15 W/m2(2 W/m2)± 4 W/m2(0.5 W/m2)± 21 W/m2(2 W/m2)± 1.5 %
(0.25 %)
±1%
(0.2 %)± 20 W/m2

60 s (1 s)± 30 W/m2(3 W/m2)± 8 W/m2(1 W/m2)± 41 W/m2(3 W/m2)±3%(0.5 %)±3%(0.5%)± 30 W/m2

For spectrally flat subcategory only:
Spectral selectivity (350 to 1 500 x 10-9 m)(WMO 300 to 3 000 x 10-9 m)
Clear sky global horizontal irradiance spectral
error
Temperature response (interval -10 to + 40
° C relative to 20 °C)**
Tilt response(0 to 180 ° at 1000 W/m2)

±3%
(2 %)

±3%
(2 %)

±3%
(2 %)

± 0.5 %
(0.1%)±1%(0.2 %)± 0.5 %
(0.2 %)±1%(0.5 %)±2%(0.2 %)±2%(0.5 %)

±5%
(1%)
±4%
(0.5 %)±5%(0.5 %)

Additional signal processing errors± 2 W/m2(2 W/m2)± 5 W/m2(2 W/m2)± 10 W/m2(2 W/m2)

Conformity testing**

Temperature anddirectional testfor every
individual
instrument
0.5 s

group
compliancegroup
compliance

0.5 s

0.5 s

Non-stability (change per year)
Non-linearity (100 to 1000 W/m2)
Directional response

For fast response subclass only:
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ADDITIONAL WMO SPECIFICATIONSWMO CLASSHIGH QUALITY

GOOD QUALITY

WMO: achievable accuracy for daily sums*

2%

5%

MODERATEQUALITY
10 %WMO: achievable accuracy for hourly sums*

3%

8%

20 %

WMO: achievable accuracy for minute sums*

not specified

not specified

not specified

WMO: resolution(smallest detectable change)

1 W/m2

5 W/m2

10 W/m2* WMO 7.2.1: The estimated uncertainties are based on the following assumptions: (a)instruments are well-maintained, correctly aligned and clean; (b) 1 min and 1 h figures are forclear-sky irradiances at solar noon; (c) daily exposure values are for clear days at mid-latitudes.
WMO 7.3.2.5: Table 7.5 lists the expected maximum deviation from the true value, excluding
calibration errors.
** ISO 9060: 2018: an instrument is subject to conformity testing of its specifications. The
classification of pyranometers may be applied to individual instruments or to groups (particular
types) of instruments, depending on the category. A pyranometer type (pyranometers of identicaldesign) may be claimed to be of a particular class even without individual tests depending on theclass if the appropriate quality control has shown that pyranometers of this type comply with therespective specifications. For the classification of a pyranometer in the highest class a, individual
tests of temperature response and directional response are required. A specification is fulfilled if: a)
the value of the respective test result lies in the corresponding acceptance interval given in Table 1
for the specific class of instrument; and if b) the sum of the absolute amounts of the expanded
uncertainty of the test and the test result is less or equal to the absolute amount of the limit of thetolerance interval (guarded acceptance) — the tolerance interval is determined by the acceptanceinterval and the guard bands from iso 9060: 2018 table 1 (same as 10.8.1). Reference: JCGM 106
and ISO /IEC Guide 98-4 Uncertainty of measurement — Part 4: Role of measurement uncertainty
in conformity assessment.

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10.8 Appendix on ISO 9060:1990 classification no longer valid
Table 10.8.1 Former classification table for pyranometers per ISO 9060:1990 and WMO.
ISO 9060:1990 has been superseded by ISO 9060:2018, see appendix 10.7.
NOTE: WMO specification of spectral selectivity is different from that of ISO. Hukseflux
conforms to the ISO limits. WMO also specifies expected accuracies. ISO finds this not to
be a part of the classification system, because it also involves calibration. Please notethat WMO achievable accuracies are for clear days at mid latitudes and that theuncertainty estimate does not include uncertainty due to calibration*.
FORMER ISO 9060:1990 CLASSIFICATION TABLE(SUPERSEDED BY ISO 9060:2018)
ISO CLASSSECONDARYSTANDARD

FIRST CLASSSECOND
CLASS

15 s+ 7 W/m2

30 s+ 15 W/m2

60 s+ 30 W/m2± 2 W/m2± 4 W/m2± 8 W/m2± 0.8 %
± 0.5 %
± 10 W/m2± 1.5 %
±1%
± 20 W/m2±3%±3%± 30 W/m2

Spectral selectivity (350 to 1 500 x 10-9 m)(WMO 300 to 3 000 x 10-9 m)
Temperature response (interval of 50 K)**

±3%

±5%

± 10 %

2%

4%8%

Tilt response(0 to 90 ° at 1000 W/m2)± 0.5 %

±2%

±5%

WMO CLASSHIGH QUALITY

GOOD QUALITY

WMO: achievable accuracy for daily sums*

2%

5%

MODERATEQUALITY
10 %WMO: achievable accuracy for hourly sums*

3%

8%

20 %

WMO: achievable accuracy for minute sums*

not specified

not specified

not specified

W/m2

W/m2

Specification limit
Response time (95 %)Zero offset a (response to 200 W/m2 net
thermal radiation)
Zero offset b (response to 5 K/h in ambient
temperature)
Non-stability (change per year)
Non-linearity (100 to 1000 W/m2)
Directional response

ADDITIONAL WMO SPECIFICATIONSWMO: resolution(smallest detectable change)
CONFORMITY TESTING***

1

5

10 W/m2

ISO 9060

individual
group
group
instrument only:
compliancecomplianceall specs mustcomply* WMO 7.2.1: The estimated uncertainties are based on the following assumptions: (a)instruments are well-maintained, correctly aligned and clean; (b) 1 min and 1 h figures are forclear-sky irradiances at solar noon; (c) daily exposure values are for clear days at mid-latitudes.
WMO 7.3.2.5: Table 7.5 lists the expected maximum deviation from the true value, excluding
calibration errors.
** At Hukseflux the expression ± 1 % is used instead of a range of 2 %.

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*** ISO 9060:1990 an instrument is subject to conformity testing of its specifications. Dependingon the classification, conformity compliance can be proven either by group- or individualcompliance. A specification is fulfilled if the mean value of the respective test result does notexceed the corresponding limiting value of the specification for the specific category of instrument.

10.9 Appendix on definition of pyranometer specifications
Table 10.9.1 Definition of pyranometer specifications (continued on next page).
SPECIFICATION

DEFINITION

SOURCE

Response time
(95 %)

time for 95 % response. The time interval between the
instant when a stimulus is subjected to a specified abruptchange and the instant when the response reaches andremains within specified limits around its final steadyvalue. The response time is a measure of the thermal
inertia inherent in the stabilization period for a final
reading.
response to 200 W/m2 net thermal radiation (ventilated).
Hukseflux assumes that unventilated instruments have to
specify the zero-offset in unventilated – worst case –conditions.
Zero offsets are a measure of the stability of the zeropoint.
Zero offset a is visible at night as a negative offset, theinstrument dome irradiates in the far infra red to therelatively cold sky. This causes the dome to cool down.
The pyranometer sensor irradiates to the relatively cooldome, causing a negative offset. Zero offset a is also
assumed to be present during daytime.
response to 5 K/h change in ambient temperature.
Zero offsets are a measure of the stability of the zeropoint.
Including the effects of zero offset a and b and othersources
percentage change in sensitivity per year. The
dependence of sensitivity resulting from ageing effects
which is a measure of the long-term stability.
percentage deviation from the sensitivity at 500 W/m2
due to the change in irradiance within the range of 100
W/m2 to 1000 W/m2.
Non-linearity has an overlap with directional response,
and therefore should be handled with care in uncertainty
evaluation.
the range of errors caused by assuming that the normal
incidence sensitivity is valid for all directions whenmeasuring from any direction (with incidence angle of up
to 90 ° or even from below the sensor) a beam radiation
whose normal incidence irradiance is 1000 W/m2 .
Directional response is a measure of the deviations fromthe ideal “cosine behaviour” and its azimuthal variation.
Appendix A5: measurement should be made at least at

ISO 9060:2018
WMO 1.6.3

Zero offset a:(200 W/m2 net
thermalradiation )Zero offset b:(5 K/h in ambient
temperature)
Total zero offset
Non-stability(change per
year)
Non-linearity(100 to 1000
W/m2)

Directional
response

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ISO 9060:2018

ISO 9060:2018

ISO 9060:2018
ISO 9060:2018

ISO 9060:2018

ISO 9060:2018

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Spectralselectivity (350
to 1500 x 10-9 m)(WMO 300 to3000 x 10-9 m)

Clear sky global
horizontal
irradiancespectral error
Temperature
response(interval of 50 K)
Tilt response(0° to 180° at
1000 W/m2)

Additional signal
processing errors

Sensitivity
Spectral range

the following directions: incidence angles of 40°, 60°,70°, 80° and 95° at four azimuth angles (e.g. 0°, 90°,180°, 270°).
percentage deviation of the product of spectral
absorptance and spectral transmittance from thecorresponding mean within 350 x 10-9 m to 1500 x 10-9 m
and the spectral distribution of irradiance. Spectral
selectivity is a measure of the spectral selectivity of thesensitivity.

ISO 9060:2018

maximum spectral error observed for a set of global
horizontal irradiance clear sky spectra defined in thisdocument ISO 9060:2018

ISO 9060:2018

percentage deviation of the sensitivity due to change inambient temperature within the interval of – 10 °C to +40 °C relative to °20 C.
percentage deviation from the sensitivity at 0° tilt
(horizontal) due to change in tilt from 0 ° to 180 ° at
1000 W/m2 irradiance. Tilt response describes changes ofthe sensitivity due to changes of the tilt angle of thereceiving surface.
The additional signal processing errors contain dataacquisition and analogue to digital conversion that might
be carried out in the instrument and all other processing
steps carried out within the instrument that are notcovered by the other specifications
the change in the response of a measuring instrument
divided by the corresponding change in the stimulus.
the spectral range of radiation to which the instrument issensitive. For a normal pyranometer this should be in the
0.3 to 3 x 10-6 m range. Some pyranometers withcoloured glass domes have a limited spectral range.

ISO 9060:2018

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ISO 9060:2018

ISO 9060:2018

WMO 1.6.3
Hukseflux

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10.10 Appendix on terminology / glossary
Table 10.10.1 Definitions and references of used terms (continued on next page).
TERM

DEFINITION (REFERENCE)

Solar energy
or solarradiation

solar energy is the electromagnetic energy emitted by the sun. Solar energy isalso called solar radiation and shortwave radiation. The solar radiation incident
on the top of the terrestrial atmosphere is called extra-terrestrial solar radiation;
97 % of which is confined to the spectral range of 290 to 3 000 x 10-9 m. Part ofthe extra-terrestrial solar radiation penetrates the atmosphere and directly
reaches the earth’s surface, while part of it is scattered and / or absorbed by thegas molecules, aerosol particles, cloud droplets and cloud crystals in theatmosphere. The former is the direct component, the latter is the diffuse
component of the solar radiation. (ref: WMO, Hukseflux)
solar radiation received by a plane surface from a 180 ° field of view angle (solid
angle of 2π sr).(ref: ISO 9060)
also GHI: the solar radiation received from a 180 ° field of view angle on ahorizontal surface is referred to as global radiation. Also called GHI. This includes
radiation received directly from the solid angle of the sun’s disc, as well as diffuse
sky radiation that has been scattered in traversing the atmosphere. (ref: WMO)
Hemispherical solar radiation received by a horizontal plane surface.
(ref: ISO 9060)
radiation received from a small solid angle centred on the sun’s disc, on a given
plane (ref: ISO 9060)
also DNI: radiation received from a small solid angle centred on the sun’s disc,on a plane normal to its direction (ref: ISO 9060)
hemispherical radiation minus coplanar direct radiation (ref: ISO 9060)

Hemisphericalsolar radiation
Global solar
radiation

Directradiation
Direct Normal
Irradiance
Diffuseradiation
DiffuseHorizontal
Irradiance
Plane of Array
irradiance

Reflected
Irradiance
Rearside
Plane of Array
irradiance
Reflected
Horizontal
IrradianceDirect solar
radiation
Terrestrial or
Longwaveradiation

also DHI: global horizontal irradiance minus coplanar direct (the portion
emanating from the solar disk and from the circumsolar region of the sky withina subtended full angle of 5°) (ref: IEC 61724-1)
also POA: hemispherical solar irradiance in the plane of a PV array.
sum of direct, diffuse, and ground-reflected irradiance incident upon the frontsideof an inclined surface parallel to the plane of the modules in the PV array (ref:ASTM E2848-11 / IEC 61724)
also RI : ground-reflected irradiance incident upon a defined surface, typicallyparallel to the plane of the modules in the (bifacial) PV arrayalso POA REAR: sum of direct, diffuse, and ground-reflected irradiance incident on
the back side of an inclined surface parallel to the plane of the modules in the PV
array (ref: IEC 61724, ISO TR 9901)
also RHI: ground-reflected irradiance incident upon a surface, oriented
horizontally facing down. (ref: IEC 61724, ISO TR 9901)
radiation received from a small solid angle centred on the sun’s disc, on a given
plane. (ref: ISO 9060)
radiation not of solar origin but of terrestrial and atmospheric origin and having
longer wavelengths (3 000 to 100 000 x 10-9 m). In case of downwelling El ↓ also
the background radiation from the universe is involved, passing through the”atmospheric window”. In case of upwelling El ↑, composed of long-wave
electromagnetic energy emitted by the earth’s surface and by the gases, aerosols
and clouds of the atmosphere; it is also partly absorbed within the atmosphere.

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WorldRadiometric
Reference(WRR)
AlbedoAngle ofincidence
Zenith angle
Azimuth angle

Sunshineduration

For a temperature of 300 K, 99.99 % of the power of the terrestrial radiation has
a wavelength longer than 3 000 x 10-9 m and about 99 per cent longer than
5 000 x 10-9 m. For lower temperatures, the spectrum shifts to longer
wavelengths. (ref: WMO)
measurement standard representing the Sl unit of irradiance with an uncertaintyof less than ± 0.3 % (see the WMO Guide to Meteorological Instruments andMethods of Observation, 1983, subclause 9.1.3). The reference was adopted by
the World Meteorological Organization (WMO) and has been in effect since 1 July
1980. (ref: ISO 9060)
ratio of reflected and incoming solar radiation. Dimensionless number that varies
between 0 and 1. Typical albedo values are: < 0.1 for water, from 0.1 for wet
soils to 0.5 for dry sand, from 0.1 to 0.4 for vegetation, up to 0.9 for fresh snow.
angle of radiation relative to the sensor measured from normal incidence (varies
from 0 ° to 90 °).
angle of incidence of radiation, relative to zenith. Equals angle of incidence forhorizontally mounted instruments
angle of incidence of radiation, projected in the plane of the sensor surface.
Varies from 0 ° to 360 °. 0 is by definition the cable exit direction, also called
north, east is + 90 °. (ASTM G113-09)
sunshine duration during a given period is defined as the sum of that sub-period
for which the direct solar irradiance exceeds 120 W/m2. (ref: WMO)

10.11 Appendix on function codes, register and coil overview
Table 10.11.1 Supported Modbus function codes.
SUPPORTED MODBUS FUNCTION CODESFUNCTION CODE (HEX)DESCRIPTION

0x01

Read Coils

0x02

Read Discrete Inputs

0x03

Read Holding Registers

0x04

Read Input Register

0x05

Write Single Coil

0x06

Write Single Holding Register

0x0F

Write Multiple Coils

0x10

Write Multiple Registers
NOTICE

Depending on processing by the network master, your data request may need
an offset of +1 for each SR30 register address. Example: SR30 register address 7+ master offset = 7 + 1 = master register address 8. Consult the manual of thelocal network master.
SR30 does not distinguish between holding registers and input registers. Therefore both
function code 0x03 and 0x04 may be used to read registers.

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Up to five 16 bit registers can be read in one request. If six or more registers are to beread, multiple requests must be used. Whenever a 32 bit parameter is being read (S32,U32 or FLOAT) both 16 bit Modbus registers must be read in a single Modbus request.
When reading the 16 bit registers separately, the parameter value may be updated in
between read requests (may become incoherent), which can lead to false readings.

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Table 10.11.2 Modbus registers 0 to 199 (continued on next pages).
MODBUS REGISTERS 0-199
REGISTERADDRESS
0

PARAMETER

1

12 to 31

Serialcommunication
settings
Irradiance(temperaturecompensated signal)
Irradiance(uncompensatedsignal)Sensor bodytemperature
Sensor electricalresistance
Scaling factor
irradiance
Scaling factor
temperature
Sensor voltage
outputFactory use only

32 to 35

Sensor model

36 to 39

Sensor model

40

Sensor serial
numberSensor sensitivity

2+3

4+5

6
7
8
9
10 + 11

41 + 4243

44

45
46 + 47

R/W

FORMAT OF
DATA
U16

R/W

U16

R

S32

R

S32

R

S16

In x 0.1 ΩRU16

Default = 100

R

U16

Default = 100

R

U16

In x 10-9 V

R

S32Part one of sensor
description
Part two of sensor
description

R

StringR

StringR

U16

In x 10-6 V/(W/m2)

R

Float

Response time as
measured duringcalibration
Sensor resistance asmeasured duringcalibration
Reserved

In x 0.1 s

RU16

In x 0.1 ΩRU16

Always 0

R

U16

Sensor calibration
date

Calibration date of
the sensor in
YYYYMMDD

R

U32

Device address

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DESCRIPTION OF
CONTENT
Sensor address in
Modbus network,
default = 1
Sets the serial
communication,
default = 5
Temperaturecompensated signal
in x 0.01 W/m²
Uncompensatedsignalin x 0.01 W/m²
In x 0.01 °C

ACCESS

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MODBUS REGISTERS 0 – 199, continued
REGISTERADDRESS
48 to 60

REGISTERADDRESS
Factory use

61

Firmware version

62

Hardware version

63 + 64

Sensor sensitivity
history 1

65 + 66

Calibration datehistory 1

67 + 68

Sensor sensitivity
history 2
Calibration datehistory 2
Sensor sensitivity
history 3
Calibration datehistory 3
Sensor sensitivity
history 4
Calibration datehistory 4
Sensor sensitivity
history 5
Calibration datehistory 5
Factory use

69 + 70
71 + 72
73 + 74
75 + 76
77 + 78
79 + 80
81 + 82
83 - 86

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REGISTERADDRESSIn x 10V/(W/m2)
Default value is 0
Formercalibration date of
the sensor in
YYYYMMDD
Default value is 0
See register 63+64
See register 65 +66
See register 63 +64
See register 65 +66
See register 63 +64
See register 65 +66
See register 63 +64
See register 65 +66
-6

REGISTERADDRESSREGISTERADDRESS

R

U16

R

U16

R

Float

R

U32

R

Float

R

U32

R

Float

R

U32

R

Float

R

U32

R

Float

R

U32

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MODBUS REGISTERS 0 – 199, continued
REGISTERADDRESS87 + 88

PARAMETERDESCRIPTION OF
CONTENTACCESSR

FORMAT
OF DATA
Float

R

Float

R

Float

In x 0.01 %R

U16

In x (1/32) mbar

R

U16

In x 0.01 °R

U16

In x 1 RPM

R

U16

93 - 97

Polynomial
temperature
coefficient a
Polynomial
temperature
coefficient b
Polynomial
temperature
coefficient c
Factory use only98

Humidity

99

Factory use

100-137

Factory use

138

Pressure average

139 - 193

Factory use

194

Tilt angle

195

Factory use

196

Fan speed RPM

197

Factory use

198

Heater current

In x 1 mA

R

U16

199

Fan current

In x 1 mA

R

U16

89 + 90

91 + 92

NOTICE
Depending on processing by the network master device, your data request may
need an offset of +1 for each SR30 register address. If so, this offset applies to coils
as well. Consult the manual of the network master device.
Table 10.11.3 Coils.
COILS
COIL

PARAMETERDESCRIPTIONTYPE OFOBJECT TYPE

0

RestartRestart the sensor

W

Single bit

1

HeaterTurn heater on/off

W

Single bit

2

Check

W

Single bit

3

Fan

Measure sensor
electrical resistanceTurn fan on/off

W

Single bit

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10.12 Appendix on electromagnetic compatibility (EMC) testing
EMC testing has been performed according to the following standards:• Emission IEC/EN 61326-1 (2013)• Immunity IEC/EN 61326-1 (2013)
Table 10.12.1 Immunity test descriptions and basic test standards used for EMC testing.
DESCRIPTIONBASIC STANDARD

Conducted emission, test with a LISN
Radiated emission up to 1 GHz(in a semi-anechoic chamber)Electrostatic discharge (ESD)
Radiated Immunity
Electrical fast transient (EFT)
Surge*
Conducted Immunity

IEC/EN 55011 (2009) + A1 (2010)
IEC/EN 55011 (2009) + A1 (2010)
IEC/EN 61000-4-2 (2009)
IEC/EN 61000-4-3 (2006) + A1 (2008) + A2 (2010)
IEC/EN 61000-4-4 (2012)
IEC/EN 61000-4-5 (2014) + A1 (2017)
IEC/EN 61000-4-6 (2014)* Only tested up to 500 V line-to-ground

Note: All emission testing has been performed under a lamp at about 200 W/m2 and all
immunity testing has been performed at about 200 W/m2 and is repeated at 300 W/m2.

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10.13 EU declaration of conformity

We,

Hukseflux Thermal Sensors B.V., Delftechpark 31, Delft,
The Netherlands

hereby declare under our sole responsibility that:
Product model:
Product type:

SR30-M2-D1
Pyranometer

conform with the following directives:
2011/65/EU, EU 2015/863
2014/30/EU
2006/42/EC
2014/35/EU

The Restriction of Hazardous Substances Directive
The Electromagnetic Compatibility Directive
The Machinery Directive
The Low Voltage Directive

This conformity is declared using the relevant sections and requirements of the following
standards
Hazardous substances
Product safety
Electrical safety
EMC Emission
EMC Immunity

RoHS 2 and EU 215/863 amendment known as RoHS 3,
IEC/ EN 63000:2018
not applicable
IEC/EN 61010-1:2010
IEC/EN 61326-1:2013, Class B (report 20200708RPT01)
IEC/EN 61326-1:2013 (report 20200708RPT01)

Eric HOEKSEMA
Director
Delft, 23 November, 2020

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© 2023, Hukseflux Thermal Sensors B.V.
www.hukseflux.com
Hukseflux Thermal Sensors B.V. reserves the right to change specifications without notice.