Hukseflux SR05, SR05-D1A3-PV User Manual

Download

USER MANUAL

SR05-D1A3-PV

Digital second class pyranometer – alternative for PV reference cell

Hukseflux

Thermal Sensors

SR05-D1A3-PV manual v1801 2/83

Warning statements

Putting more than 30 Volt across the sensor wiring of the main power supply can lead t o permanent damage to the sensor.

Keep the voltage on the RS-485 data wiring of SR05-D1A3-PV between -7 and +12 V to avoid permanent damage.

For proper instrument grounding: use SR05 with its original factory-made SR05 cable.

Using the same Modbus address for more than one device will lead to irregular behaviour of the entire network.

Disconnect power whi le performing service or maintenance.

Locally connect the cable shield to ground if SR05-D1A3-PV is not connected to ground throu gh the installation platform.

Modbus

is a registered trademark of Schneider Electric, licens e d to the Modb us Organization, Inc.

SR05-D1A3-PV manual v1801 3/83

Contents

Warning statements 2 Contents 3 List of symbols 5 Introduction 6 1 Ordering and checking at delivery 11

1.1 Ordering SR05-D1A3-PV 11

1.2 Included items 13

1.3 Quick instrument check 14

2 Instrument principle and theory 15 3 Specifications of SR05-D1A3-PV 18

3.1 Specifications of SR05-D1A3-PV 18

3.2 Dimensions of SR05 22

4 Standards and recommended practices for use 23

4.1 Classification standard 23

4.2 General use for solar radiation measurement 23

4.3 General use for sunshine duration measurement 23

4.4 Specific use for outdoor PV system perfo rmance testing 24

4.5 Specific use in meteorology and climatology 25

5 Installation of SR05 26

5.1 Site selection and installation 26

5.2 Mounting and levelling SR05 27

5.3 Installing SR05 27

5.4 Installing SR05 with its ball levelling and tube mount 28

5.5 Placing and removing SR05’s ball levelling shim 30

5.6 Electrical connection of SR05-D1A3-PV: wiring diagram 32

5.7 Grounding and use of t he shield 32

5.8 Using SR05-D1A3-PV’s digital output 33

5.9 Using SR05-D1A3-PV’s analogue 0 to 1 V output 36

6 Communication with SR05 37

6.1 PC communication: Sensor Manager software 37

6.2 Network communication: function codes, registers, coils 43

6.3 Silicon Reference Cell compatible Modbus output 45

6.4 Standard Hukseflux Modbus Output 48

6.5 Network communication: getting started 53

6.6 Network communication: example master reques t to SR05 54

7 Making a dependable measurement 56

7.1 The concept of dependability 56

7.2 Reliability of the measurement 57

7.3 Speed of repair and maintenance 58

7.4 Uncertainty evaluation 58

8 Maintenance and trouble shooting 61

8.1 Recommended maintenance and quality assurance 61

8.2 Trouble shooting 62

8.3 Calibration and che cks in the field 63

8.4 Data quality assurance 64

9 Appendices 66

9.1 Appendix on cable extension / replacement 66

9.2 Appendix on tools for SR05 68

9.3 Appendix on spare parts for SR05 68

SR05-D1A3-PV manual v1801 4/83

9.4 Appendix on standards for classification and calibration 69

9.5 Appendix on calibration hierarchy 70

9.6 Appendix on meteorological radiation quantities 71

9.7 Appendix on ISO and WMO classification tables 72

9.8 Appendix on definition of pyranometer specifications 73

9.9 Appendix on terminology / glossary 74

9.10 Appendix on floating point format conversion 75

9.11 Appendix on function codes, register and co il overview 76

9.12 Appendix on the sensor model name in the register 80

9.13 EU declaration of conformity 81

SR05-D1A3-PV manual v1801 5/83

List of sy m bols

Quantities Symbol Unit Voltage output U V

Sensitivity S V/(W/m

)

Solar irradiance E W/m

Output of 0-1 V U V Transmitted range of 0-1 V r W/m

(see also appendix 9.6 on meteorological qua ntities)

Subscripts

Not applicable

Notation Example

Decimal numbers are indicated without prefix 30 Hexadecimal numbers are indicated with a 0x prefix 0x1E

SR05-D1A3-PV manual v1801 6/83

Introduction

SR05 series is the most affordable range of pyranometers meeting ISO 9060 requirements. These sensors are ideal for general solar radiation measurements and popular for monitoring photovoltaic (PV) systems. Model SR05-D1A3–PV is made as a perfect alternative to PV reference cells. It offers the same Modbus interface as the most common PV reference cell model for easy compatibility. Relative to PV reference cells, SR05-D1A3-PV has the advantage of higher stability, independence of the PV cell type or anti-reflection coating, and better availability and price of recalibration.

SR05 series is an economical range of ISO 9060 second class pyranometers for measurement of solar radiation received by a plane surface, in W/m

, from a 180 ° field of view angle. SR05 is perfect for predicting generated power and monitoring the overall efficiency of PV power plants. Different mounting options are available, allowing SR05 to be mounted in virtually any situation. The combination of easy installation and its low cost makes SR05 the preferred solution for commercial scale PV systems.

There are several versions of SR05 series:

• Version SR05-D1A3: digit al s e nsor wit h Mo db us ove r RS-485 and analogue 0-1 V output

• Version SR05-D2A2: digit al s e nsor wit h Mo db us ove r TTL and ana log ue 4–20 mA output

• Version SR05-A1: analogue senso r w it h an a log u e m ill iv olt output

and:

•

Version SR05-D1A3-PV: d igit al se nso r w ith M odb us o ver RS-485, alternative for PV

reference cell

This user manual covers use of SR05-D1A3-PV. Specifications of this version differ from those of the other digital and analogue sensors in the SR05 series range. For use of SR05-D1A3 or SR05-D2A2, consult the separate SR05-D1A3 & SR05-D2A2 user manual. For use of SR05-A1, offering analogue millivolt output, consult the separate SR05-A1 user manual.

Figure 0.1 SR05-D1A3-PV digital second class pyranometer seen from above

SR05-D1A3-PV manual v1801 7/83

Model SR05-D1A3-PV has a digital output that is identical to the most commonly used photovoltaic reference cell with Modbus over RS-485 output. This allows for easy installation in existing PV monitoring systems, without the need to make major modifications to data logging software, instrument libraries and infrastructure.

Compared to silicon reference cells, pyranometers offer several advantages such as a perfect (cosine) directional response and a flat spectral response over a wide range. Pyranometers therefore meas ure the maximum available resource and are suitable to act as a reference for all types (for example amorphous, crystalline or thin-film) of photovoltaic cells both with and without anti-reflection coating. See also our Application note “pyranometers versus PV reference cells”. Moreover, since the working principle of a pyranometer is different from a solar cell, the pyranometer offers a truly independent measurement of the irradiance.

PV system performance monitoring: compliant with IEC 61724-1, Class C

IEC 61724-1: Photovoltaic System Performance Monitoring - Guidelines for Measurement, Data Exchange and Analysis – suggests to use pyranometers for PV monitoring; SR05 complies with IEC 61724-1 class C system requirements.

Features and benefits of SR05-D1A3-PV

• higher stability than PV reference cells

• indepen den t of P V ce ll typ e

• affordable calibration

• register structure and content identical to most common reference cells for easy

exchangeability

• easy imple me nta tio n an d ser vic ing

• easy mou n tin g a n d le v e llin g

• pricing: affordable second class pyranometers

Figure 0.2 Two SR05-D1A3-PV digital second class pyranometers, of which one measuring in Plane of Array, replacing PV reference cells

SR05-D1A3-PV manual v1801 8/83

SR05-D1A3-PV design

SR05 pyranometers employ a thermopile sensor with black coated surface, one dome and an anodised aluminium body with visible bubble level. Optionally the sensor can be delivered with a unique ball levelling mechanism and tube mount or dedicated mounting fixture, for easy installation. SR05-D1A3-PV has an industry standard digital output: Modbus RTU over half-duplex RS-485, that allows multiple sensors to be installed on a single network. In addition, SR05-D1A3-PV has analogue 0 to 1 V output.

Figure 0.3 On the left SR05-D1A3-PV pyranometer with bubble level and M12-A cable connector in its standard configuration (3 metre ca ble standard included); on the right SR05 with optional ball levelling, for easy mounting and levelling on (non-)horizontal surfaces (included mounting bolts not displayed)

Figure 0.4 SR05-D1A3-PV digital second class pyranometer with optional ball levelling and tube mount for easy mounting and levelling on a tube (tube not included)

SR05-D1A3-PV manual v1801 9/83

Communication with a PC: Hukseflux Sensor Manager Software

For communication between a PC and SR05-D1A3-PV(‘s), the Hukseflux Sensor Manager software can be used. It is available for download on our website. The software allows the user to quickly configure SR05-D1A3-PV Modbus address and serial communication settings (baud rate, parity and stopbits) and to plot and export data. Also, the digital outputs may be viewed for sensor diagnostics.

Figure 0.5 U

ser

interface of the Hukseflux Sensor Manager

Compatibility

SR05-D1A3-PV’s Modbus interface is exchangeable with IMT-Solar Si-RS485TC-T-MB PV reference cell’s interface. Other reference cells upon request.

Suggested use for SR05-D1A3-PV

• replacement of PV reference cells

• measuring global tilted irradiance (GTI) in the Plane of Array (PoA) of solar panels

• measuring global horizontal irradiance (GHI)

SR05-D1A3-PV is suited 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 slave. Using SR05-D1A3-PV in a network is easy. Once it has the correct Modbus address and communication settings and is connected to a power supply, the instrument can be used in RS-485 networks. A typical network wil l request the irradiance (either register 0x0000 or registers 0x1002 + 0x1003) and temperature data (either register 0x0007 or register 0x1006) every 1 second, and eventually store the averages every 60 seconds. How to issue a request, process the register content and convert it to useful data is described in the paragraphs about network communication. The user should have sound knowledge of the Mo db us communication protocol when installing sensors in a network. When using the analogue 0 to 1 V output provided by SR05-D1A3-PV, the instrument can be connected directly to commonly used datalogging systems capable of handling a 0 to 1 V signal.

SR05-D1A3-PV manual v1801 10/83

The recommended calibration interval of pyranometers is 2 years. The registers containing the applied sensitivity and the ca libra tion history of the digital versions of SR05 are accessible for users with a password. This allows the user to choose his own local calibration service. The same register access may also be used for remotely controlled re-calibration of pyranometers in the field. Ask Hukseflux for information on this feature and on ISO and ASTM standardised procedures for field calibration.

The ASTM E2848 “Standard Test Method for Reporting Photo voltaic Non-Concentrator System Performance” (issued end 2011) confirms that a pyr anometer is the preferred instrument for PV system performance monitoring. SR05 pyranometer complies with the requirements of this standard. For more information, see our pyranometer selection

guide.

WMO has approved the “pyranometric method” to calculate sunshine duration from pyranometer measurements in WMO-No. 8, Guide to Meteorological Instruments and Methods of Observation. This implies that SR05 may be use d, in combination with appropriate software, to estimate sunshine duration. This is much more cost-effective than using a dedicated sunshine duration sensor. Ask for our application note.

All SR05 versions should be used in accordance with the recommended practices of ISO, WMO and ASTM.

See also

• view our comp lete range of sensors

• PMF01 pyranometer mounting fixture, compatible with SR05 ball levelling

SR05-D1A3-PV manual v1801 11/83

1 Ordering and checking at delivery

1.1 Ordering SR05-D1A3-PV

SR05-D1A3-PV second class pyranometer has a digital output that is identical to the most commonly used photovoltaic reference cell with Modbus over RS-485 output.

Besides SR05-D1A3-PV, SR05 series offers several other versions with industry standard outputs, both digital and analogue. Each version offers multiple mounting options and various cable lengths:

• SR05-D1A3 digital second class sensor, with Modbus over RS-485 and 0-1 V output

• SR05-D2A2 digital second class sensor, with Modbus over TTL and 4-20 mA output

• SR05-A1 analogue second class pyranometer with millivolt output

This is our standard Modbus model which is not directly exchangeable with the commonly used PV reference cells.

For an overview of all versions and options, and how to order, please take a look at Table

1.1.1 on the next page.

The standard configuration of SR05-D1A3-PV is with 3 metres cable length. Common options for SR05-D1A3-PV are:

• longer cable (10, 20 metres). Specify total cable length

• extension cable with connector pair (10, 20 metres). Specify total cable length

• with ball levelling (-BL)

• with ball levelling and tube mount (for tube diameters 25 to 40 mm, -TMBL)

Ball levelling and tube m ount are suited for retrofitting.

SR05-D1A3-PV’s Modbus interface is exchangeable with IMT-Solar Si-RS485TC-T-MB PV reference cell’s interface. Other reference cells upon request.

SR05-D1A3-PV manual v1801 12/83

Table 1.1.1 Ordering codes for the versions of model SR05

VERSIONS OF SR05 (part numbers), without cable

SR05-D1A3-PV

digital second class pyranometer, with Modbus ove r

RS-485 output, alternative for PV reference cell

SR05-D1A3-PV-BL

digital second class pyranometer, with Modbus ove r RS-485 output, alternative for PV reference cell, with ball

levelling

SR05-D1A3-PV-TMBL

digital second class pyranometer, with Modbus ove r RS-485 output, alternative for PV reference cell, with tube

mount on ball levelling

SR05-D1A3

digital second class pyranometer, with Modbus ove r

RS-485 and 0-1 V output

SR05-D1A3-BL

digital second class pyranometer, with Modbus ove r RS-485 and 0-1 V output, with ball levelling

SR05-D1A3-TMBL

digital second class pyranometer, with Modbus ove r

RS-485 and 0-1 V output, with tube mount on ball

levelling

SR05-D2A2

digital second class pyranometer, with Modbus ove r TTL and 4-20 mA output

SR05-D2A2-BL

digital second class pyranometer, with Modbus over TTL

and 4-20 mA output, with ball levelling

SR05-D2A2-TMBL

digital second class pyranometer, with Modbus ove r TTL

and 4-20 mA output, with tube mount on ball levelling

SR05-A1

analogue second class pyranometer, with millivolt output

SR05-A1-BL

analogue second class pyranometer, with millivolt output,

with bal l le v elling

SR05-A1-TMBL

analogue second class pyranometer, with millivolt output, with tube mount on ball levelling

CABLE FOR SR05, with female M12-A connector at sensor end, non-stripped on other end

‘-03’ after SR05 part number

standard cable length: 3 m

‘-10’ after SR05 part number

cable length: 10 m

‘-20’ after SR05 part number

cable length: 20 m

CABLE EXTENSION FOR SR05, with male and female M12-A connectors

C06E-10

cable length: 10 m

C06E-20

cable length: 20 m

An extension cable (wit h connector pair) can be used in combination w ith a regular cable (with one connector at sensor end) to make alternative SR0 5 cable lengths possible.

Example: Cable length needed: 15 m. In this case, it is eas iest to buy SR05 with a 20 m cable and to cut it to desired length.

Example: Cable length needed: 30 m. In this case, it is eas iest to buy SR05 with 10 m cable and a cable extension of 20 m.

SR05-D1A3-PV manual v1801 13/83

1.2 Included items

Arriving at the customer, the delivery should include:

• pyranometer SR05-D1A3-PV

• cable of the length as ordered

• product certificate matching the instrument serial number

For SR05-D1A3-PV-BL, also

• ball levelling

• 4 mm hex key

• 1 x shim

• 2 x M5x20 bolts

• 2 x M5 nuts

For SR05-D1A3-PV-TMBL, also

• ball levelling

• 4 mm hex key

• 1 x shim

• 2 x M5x20 bolts

• 2 x M5 nuts

• tube mount

• 2 x M5x30 bolts

• 2 x M5x40 bolts

Please store the certificate in a safe place. The Hukseflux Sensor Manager can be downloaded via www.hukseflux.com/downloads

SR05-D1A3-PV SR05-D1A3-PV-BL SR05-D1A3-PV-TMBL

Figure 1.2.1 From left to right: SR05-D1A3-PV, SR05-D1A3-PV-BL and SR05-D1A3-PV-

TMBL (nuts and bolts, tools and certificates are not shown, tube itself is not included)

SR05-D1A3-PV manual v1801 14/83

1.3 Quick instrument check

A quick test 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.

1. At power–up the signal may have a temporary output level different from zero; an offset. Let this offset settle down.

2. Check if the sensor reacts to light: expose the se nso r to a strong light source, for instance a 100 W light bulb at 0.1 m distance. The signal should read > 100 W/m

now. Darken the sensor either by putting something over it or switching off the light. The instrument irradiance output should go down and within one minute approach 0 W/m

3. Inspect the bubble level.

4. Inspect the instrument for any damage.

5. Check the instrument serial number as indicated by the software against the label on the instrument and against the certificates provided with the instrument.

SR05-D1A3-PV manual v1801 15/83

2 Instrument principle and theory

Figure 2.1 Overview of SR05: shaded areas in exploded view show ball levelling mount and shim

(1) cable (standard length 3 metres, optional longer cable) (2) connector (3) bubble level (4) thermal sensor with black coating (5) glass dome (6) sensor body (7) tube mount (optional) (8) mounting screw (included with ball levelling and tube mount; requires 4 mm hex key) (9) shim (included with and needed for ball levelling mount) (10) ball levelling mount (optional) (11) countersunk set screw for levelling adjustment (included with ball levelling mount;

requires 4 mm hex key)

(12) opening for Ø 25 to Ø 40 mm tube when using ball levelling and tube mount

SR05-D1A3-PV manual v1801 16/83

SR05’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/m

, 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 that

spectral range with a spectral selectivity that is as “flat” as possible.

In an irradiance measurement by definition the response to “beam” radiation varies with the 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 pyranometer should have a so-called “directional response” (older documents mention “cosine response”) that is as close as possible to the ideal cosine characteristic.

In order to attain the proper directional and spectral characteristics, a pyranometer’s main components are:

• a thermal sensor with black coating. It has a flat sp ectrum covering the 200 to 50000

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. The thermopile sensor generates a voltage output signal that is proportional to the solar irradiance.

• 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 v iew angle. Another function of the dome is that it shields the thermopile sensor from the environment (conve ction, rain).

• The digital versions of model SR05 have a high-end 24-bit A/D converter, which is used by SR05 to convert the analogue thermopile voltage to a digital signal. SR05D1A3-PV has a digital output that is identical to the most commonly used photovoltaic reference cell with Modbus over RS-485 output for easy exchangeability.

Pyranometers can be manufactured to different specifications and with different levels of verification and characterisation during production. T he ISO 9060 - 1990 standard, “Solar energy - specification and classification of instruments for measuring hemispherical solar and direct solar radiation”, distinguishes b etween 3 classes; secondary standard (highest accuracy), first class (second highest accuracy) and second class (third highest accuracy).

From second class to first class and from first class to secondary standard, the achievable accuracy improves by a factor 2.

SR05-D1A3-PV manual v1801 17/83

Figure 2.2 Spectral response of the pyranometer compared to the solar spectrum. The pyranometer only cuts off a negligible part of the total solar spectrum.

0,2

0,4

0,6

0,8

1,2

100 1000 10000

relative spectral conten t /

response [arbitrary units]

wavelength [x 10

-9

solar radiation

pyranometer

response

SR05-D1A3-PV manual v1801 18/83

3 Specifications of SR05-D1A3-PV

3.1 Specifications of SR05-D1A3-PV

SR05 pyranometers measure the solar radiation received by a plane surface from a 180 ° field o f view angle . This quantity, expressed in W/m

, is called “hemispherical” solar

radiation.

SR05-D1A3-PV offers irradiance in W/m

as a digital output and as a 0-1 V output. It must be used in combination with suitable power supply and a data acquisition system which uses the Modbus communication protocol over RS-485 or one that is capable of handling a 0-1 V signal.

The instrument is classified according to ISO 9060 and should be used in accordance with the recommended practices of ISO, IEC, WMO and ASTM.

Table 3.1.1 Specificat ions of SR05-D1A3-PV (continued on next pages)

SR05-D1A3-PV MEASUREMENT SPECIFICATIONS: LIST OF CLASSIFICATION CRITERIA OF ISO 9060*

ISO classification (ISO 9060: 1990)

second class pyranometer

WMO performance level (WM O -No. 8,

seventh edition 2008)

moderate quality pyr a nometer

Response time (95 %)

18 s

Zero offset a (response to 200 W/m2

net thermal radiat ion)

< 15 W/m2 unventilated

Zero offset b (response to 5 K/h

change in ambient temperature)

< ± 4 W/m2

Non-stability

< ± 1 % change per year

Non-linearity

< ± 1 % (100 to 1000 W/m2)

Directional resp onse

< ± 25 W/m2

Spectral selectivity

< ± 5 % (0.35 to 1.5 x 10

-6

Temperature response

< ± 3 % (-10 to +40 °C)

Tilt response

< ± 2 % (0 to 90 ° at 1000 W/m2)

*For the exact definition of pyranometer ISO 9060 specifications see the appendix.

SR05-D1A3-PV manual v1801 19/83

Table 3.1.1 Specifications of SR05-D1A3-PV (continued)

SR05-D1A3-PV

ADDITIONAL SPECIFICATIONS

Measurand global irradiance

(hemispherical solar radiation)

Measurand in SI r a diometry units

irradiance in W/m2

Optional measurand

sunshine duration

Field of view angle

180 °

Measurement range

0 to 2000 W/m2

Spectral range

(20 % transmission p oints)

285 to 3000 x 10-9 m

Rated operating temperatu r e r a nge

-40 to +80 °C

Output definition running average over 4 last meas urements,

measurement every 0.1 s

Recommended data reques t in terval

1 s, storing 60 s averages

Measurement function / optional

programming for sunshine duration

programming according to W M O guide paragraph

8.2.2

Measurand

instrument body temperat ure

Temperature sensor

Solid state System on Chip (SoC) silicon bandgap temperature sensor

measurand in SI units

temperature in °C

Standard governing use of the

instrument

ISO/TR 9901:1990 Solar en er gy -- Field pyranometers

-- Recommended practice for u s e ASTM G183 - 05 Standa r d P r a c tice for Field Use of

Pyranometers, Pyrheliometers and UV Radiometer s

Standard cable length (see options)

3 m

Cable diameter

4.8 x 10-3 m

Cable conductor cross-section

0.25 x 10-6 m2 (24 AWG)

Chassis connector

M12-A straight male connector, male thread, 5-pole

Cable connector

M12-A straight female connector, female thread, 5pole

Connector protec tion class

IP67

Cable replacement

replacement and extension c a bles with connector(s) can be ordered separately from Hukseflux

Mounting (see opti ons)

2 x M5 bolt at 46 mm centre-to-centre distance on north-south axis, r equires 4 mm hex key

Levelling (see op tions)

bubble level is included

Levelling accuracy

< 0.6 ° bubble entirely in ring

Desiccant

silica gel, 1.0 g, in a HDPE bag, (25 x 45) mm

IP protection cla s s

IP67

Gross weight including 3 m cable

0.45 kg excluding optional a c c es s or ies

Net weight including 3 m cable

0.35 kg excluding optional a c c es s or ies

Packaging

box of (170 x 100 x 80) mm

CALIBRATION

Calibration trace a b ility

to WRR

Calibration hierarchy from WRR through ISO 9846 and ISO 9847, applying

a correction to ref er e nce conditions

Calibration method

indoor calibration according to ISO 9847, Type IIc

Calibration un certainty

< 1.8 % (k = 2)

Recommended recalibrati on interval

2 years

Reference conditions

20 °C, normal incide nce solar radiation, horizonta l mounting, irradiance level 1000 W/m2

Validity of calibra tion

based on experience the ins trument sensitivity will not change during storage. Durin g use under exposure to solar radiation th e instrument “non-stability” specification is applicable.

SR05-D1A3-PV manual v1801 20/83

Table 3.1.1 Specifications of SR05-D1A3-PV (started on previous pages)

MEASUREMENT ACCURACY AND RESOLUTION

Uncertainty of the measurement statements about the overall measurement

uncertainty ca n only be made on an individual basis.

see the chapter on uncertainty evaluation

WMO estimate on achievable accuracy for daily sums (see appendix for a

definition of the measurement conditions)

10 %

WMO estimate on achievable accuracy

for hourly sums (see appendix for a definition of the measurement conditions)

20 %

Irradiance resolution 0.1 W/m2 (register address 0x0000)

0.01 W/m2 (register address 0x1002 + 0x1003)

Instrument body temperature resolution 0.1 °C (register address 0x0007)

0.01 °C (register address 0x 1006)

Instrument body temperat ure accuracy

± 0.5 °C

SR05-D1A3-PV

Rated operating voltage ra nge

5 to 30 VDC

Recommended operating voltage

12 VDC

Power consumption

< 48 x 10-3 W at 12 VDC

SR05-D1A3-PV: DIGITAL

Digital output irradiance in W/m2

instrument body temperat ure in °C

Communication pr otocol

Modbus over 2-wire RS-485

Transmission mode

RTU

RS-485 transceiver common mode range

-7 to +12 V

RS-485 transceiver type

2-wire, non-isolated

System requirements for us e with PC Windows 7 and later, USB or RS-232 (COM) port and

connector, RS-485 / USB converter or RS-485 / RS-

232 converter

Software requirements for use with PC

Java Runtime Environment 8 – latest version available

free of charge at http://www.java.com, Hukseflux Sensor Manager - software version v1817 or higher

User interface on PC Hukseflux Sensor Man a ger v1817 or higher software

downloadable: to download and for available software updates, see

http://www.hukseflux.com/page/downloads

SR05-D1A3-PV: ANALOGUE 0 TO 1 V

0 to 1 V output

irradiance in W/m2

Transmitted range

0 to 1600 W/m2

Output signal

0 to 1 V

Standard setting (see options) 0 V at 0 W/m2 and

1 V at 1600 W/m

OPTIONS

Longer cable: 10,20 m

Cable with M12-A female c onnector on

sensor end, non-stripped on other end

option code = total cable length

Extension cable with connector pair: 10, 20 m. Cable with male and fem a le M12-A connectors

option code = C06E-10 for 10 metres, C06E-20 for 20 metres

SR05-D1A3-PV manual v1801 21/83

Table 3.1.1 Specifications of SR05-D1A3-PV (started on previous pages)

Ball levelling mountab le on (non-)horizontal surfaces

with angle compens ation up to 10 °; retrofittable; one shim, two M5x20 mounting bolts and two M5 nuts included; requires 4 mm hex k ey for levelling and 4 mm hex key and 8 mm wrench for mounting

option code = BL

Tube mount with b a ll le velling

mountable on tubes Ø 25 to Ø 40 mm

with angle compen s ation up to 10 °; retrofittable; one shim, two M5x 3 0 a nd two M5x40 mounting bolts included; requires 4 m hex key for levelling and mounting

option code = TMB L

Alternative pyranometer mounting

fixture

for mounting an y H ukseflux pyranometer on

horizontal and v er tical tubes, on platforms, both horizontal and in Plane of Array order code = PMF01

PMF01 is compatible with SR05 ball levelling

Adapted transmitted range 0 to 1 V

can be adjusted at the factory upon request

SR05-D1A3-PV manual v1801 22/83

3.2 Dimensions of SR05

Figure 3.2.1 Dimensions of SR05 in x 10

-3

m. The bottom drawing shows the height of SR05 combined with its optional ball levelling mount and the tube diameter required for use with SR05’s optional tube mount. M5 mounting bolts and the countersu nk set screw require a 4 mm hex key for mounting and levelling.

SR05-D1A3-PV manual v1801 23/83

4 Standards and recommended practices

for use

Pyranometers are classified according to the ISO 9060 standard and the WMO-No. 8 Guide. In any application the instrument should be used in accordance with the recommended practices of ISO, IEC, WMO and / or ASTM.

4.1 Classification standard

Table 4.1.1 Standards for pyranometer classification. See the appendix for definitions of

pyranometer specifications, and a table listing the specification limits.

STANDARDS FOR INSTRUMENT CLASSIFICATION

ISO STANDARD EQUIVALENT

ASTM STANDARD

WMO

ISO 9060:1990 Solar energy -- specification and classification of instruments for measuring hemispherical solar and direct solar radiation

Not available

WMO-No. 8; Guide to Meteorological Instruments and Methods of Observation, chapter 7, measurement of radiation, 7.3 measurement of global and diff use 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 RADIATION

ISO STANDARD

EQUIVALENT

ASTM STANDARD

WMO

ISO/TR 9901:1990 Solar energy -- Field pyranometers -- Recommended practice for use

ASTM G183 - 05 Standard Practice for Field Use of Pyranometers, Pyrheliometers and UV Radiometers

WMO-No. 8; Guide to Meteorological Instruments and Methods of Observation, chapter 7, measurement of radiation, 7.3 measurement of global and diff use solar radiation

4.3 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/m

SR05-D1A3-PV manual v1801 24/83

WMO has approved the “pyranometric method” to estimate sunshine duration from pyranometer measurements (Chapter 8 of the WMO Guide to Instruments and Observation, 2008). This implies that a pyranometer may be used, in combination with appropriate software, to estimate sunshine duration. Ask for our application note.

Table 4.3.1 Standards with recommendations for instrument use in sunshine duration measurement

STANDARDS FOR INSTRUMENT USE FOR SUNSHINE DURATION

WMO

WMO-No. 8; Guide to Meteorological Instruments and Methods of Observation, chapter 8, measurement of s unshine duration, 8.2.2 Pyranometric Method

4.4 Specific use for outdoor PV system performance testing

Pyranometers are used for monitoring PV power plant efficiency, in order to measure incoming solar radiation independently from the PV system. Pyranometers can be placed in two positions:

• plane of array (POA), parallel to the PV panels, for measurement of the in-plane

irradiance (also noted as G

i in IEC 61724-1)

• horizontally, for measurement of the global horizontal irradiance (E, also noted as GHI in IEC 61724-1)

SR05 series is applicable in outdoor PV system performance testing. See also Huks eflux model SR15-D1 “digital first class pyranometer” and SR30-D1 “digital secondary standard pyranometer”.

Table 4.4.1 Standards with recommendations for i n strument use in PV system performance testing

STANDARDS ON PV SYSTEM PERFORMANCE TESTING

IEC / ISO STANDARD

EQUIVALENT ASTM STANDARD

IEC 61724-1; Photovoltaic system performance monitoring – guidelines for measurement, data exchange and analysis

COMMENT: Allows pyranometers or reference cells according to IEC 60904-2 and -6. Pyranometer reading requi r ed a c c uracy better than 5% of reading (Par 4.1)

COMMENT: equals JISC 8906 (Ja pa nese Industrial Standards Committee)

ASTM 2848-11; Standard Test M ethod for Reporting Photovoltaic Non-Concentrator System Performance

COMMENT: confirms that a pyranometer is the preferred instrument for outdoor PV testing. Specifically recommends a “first class” pyranometer (paragraph A 1. 2.1.)

SR05-D1A3-PV manual v1801 25/83

4.5 Specific use in meteorology and climatology

The World Meteoro logical Org anization (W MO) is a specialised agency of the United Nations. It is the UN system's authoritative voice on the state and behaviour of the earth's atmosphere and climate. WMO publishes WMO-No. 8; Guide to Meteorological Instruments and Met hod s of Observation, in which a table is included on “level of performance” of pyranometers. Nowadays WMO conforms itself to the ISO classification system.

SR05-D1A3-PV manual v1801 26/83

5 Installation of SR05

5.1 Site selection and installation

Table 5.1.1 Recommendations for installation of pyranometers

Location

the situation that shadows are cast on the instruments

is usually not des ir a b le. The horizon should be as free from obstacles as possible. Ideally there should be no objects between the course of th e s un and the instrument.

Mechanical mounting / thermal insulation preferably use the ball levelling mount to mount SR05

to a (non-)horizontal surface. A pyranometer is sensitive to therm a l shocks. Do not mount the instrument on objec ts that become very hot (black coated metal plates).

Instrument moun ting with 2 bolts 2 x M5 bolt at 46 mm centre-to-centre distance on

north-south ax is , connection through the sensor bottom in SR05’s s tandard configuration.

with ball levelling option: 2 x M5 bolt at 46 mm centre-to-centre distance, con nection through ball levelling mount, M5x20 bolts and M5 nuts inc lu ded.

with ball levelling on tube mount option: 2 x M5 bolt at 46 mm centre-to-centre distance, connection through tube and ball levelling m ount, M5x30 and M5x40 bolts included.

Performing a representativ e

measurement

the pyranometer measures the solar radiation in the

plane of the sensor . This may require installation in a tilted or inverted position. The black sensor surface (sensor bottom plate) should be m ou nted parallel to the plane of interest. In case a pyranometer is not mounted horizontally or in case the horizon is obstructed, the representativeness of th e loca tion becomes an important element of the meas urement. See the chapter on uncertainty evaluation.

Levelling

in case of horizontal mounting use the bubble level

and optionally the ball leve lling mount. The bubble level is visible and c a n be inspected at all times.

Instrument orientation

by convention w ith the cable exit pointing to the

nearest pole (so the cable exit should point north in the northern hemisphere, south in the southern hemisphere).

Installation height in case of inverte d installation, WMO recommends a

distance of 1.5 m between soil surface and sensor (reducing the effect of sh adows and in order to obtain good spatial averaging).

SR05-D1A3-PV manual v1801 27/83

5.2 Mounting and levelling SR05

SR05 in its standard configuration is equipped wit h a visible b ubble leve l and two mounting holes. For easy mounting and levelling on a (non-)horizontal surface, SR05’s optional ball levelling is recommended. Ball levelling offers:

• easy levelling

• easy cable orientation

• easy instrument exchange

• easy mounting (mounting bolts and nuts included)

When installing SR05, ball levelling allows SR05 to rotate 360 ° and to tilt up to 10 °. This allows compensation for up to a ten degree angle when installing on a nonhorizontal surface. A 4 mm hex key (un)locks the ball levelling mechanism. When using a tube or rod for installing SR05, the optional tube mount is recommended. Combined with ball levelling it allows mounting to a 25 to 40 mm diameter tube with the same ease of levelling and instrument exchange.

Figure 5.2.1 From left to right: SR05 in its standard configuration with 3 metre cable; with optional ball levelling for easy mounting and levelling on a (non-)horizontal surface; with optional ball levelling and tube mount for easy installation on a 25 to 40 mm diameter tube. Mounting bolts are included with the ball levelling and / or tube mount.

5.3 Installing SR05

SR05 without ball levelling and tube mounting options can be mounted using two M5 bolts (not included). For the required bolt lengths, 5 to 7 mm should be added to the thickness of the user’s mounting platform. See the chapter on required tooling.

SR05 SR05-BL SR05-TMBL

SR05-D1A3-PV manual v1801 28/83

5.4 Installing SR05 with its ball levelling and tube mount

Two M5x20 bolts and two M5 nuts are included with SR05’s ball levelling option. These are to be used to mount SR05 with its ball le v e l l in g to a (non-)horizontal surface.

Two M5x30 bolts and two M5x40 bolts are included with SR05’s tube mount with ball levelling. These bolts are to be used to clamp both ball levelling and tube mount to a 25 to 40 mm diameter tube. For tube diameters larger than or equal to 33 mm, use the M5x40 bolts instead of the M5x30 bolts for a secure fit.

The unique ball head mechanism of SR05’s ball levelling mount is used to level SR05. When ordering ball levelling with SR05, it is delivered attached to SR05. In that case follow steps 1 to 7 below to mount and level SR05. Make sure the glass dome is protected at all times.

In case SR05 is not attached to its ball levelling mount yet, the user has to ensure a shim is placed properly in the centre of the bottom plate of S R0 5 before mounting and levelling. The shim allows smooth levelling and is shown top left in Figure 5.4.1. See chapter 5.5 for placing SR05’s ball levelling shim. Whe n ordering SR05 c ombined with ball levelling, the shim is already positioned in its place in the factory.

Figure 5.4.1 On the left SR05’s ball levelling including shim (mounting bolts not displayed) and on the right SR05 placed on the ball levelling mount. Loosen the countersunk set screw on SR05’s side to unlock, allow ing placement of the ball head and SR05 levelling, and tighten it to lock the ball head mechanism. A 4 mm hex key is the only tool needed to place and remove the ball levelling and to allow and disallow levelling adjustment. The shim, included when ordering ball levelling, allows for smooth levelling and should be positioned properly in the centre of the bottom plate of SR05.

1) Loosen SR05’s countersunk set screw with a 4 mm hex key by turning the hex key

counter clockwise until th e screw is slightly protruding (sticking out).

SR05-D1A3-PV manual v1801 29/83

2) Hold SR05 in one hand, the ball levelling mount in t he other.

3) Separate SR05 from the ball levelling mount by gently pulling out the ball levelling

mount.

4) Mount the ball levelling to a surface or platform with its M5 bolts and nuts. See

chapter on tooling required.

5) Place SR05 on the ball levelling mount by gently pushing the sensor onto the ball

head until it clicks.

6) SR05 can now be rotated 360 ° on its ball head by hand. This rotation allows easy

cable orientation adjustment. It can be tilted up to 10 °. This allows angle compensation on non-horizontal surfaces up to 10 °.

7) When SR05 is mounted and levelled, judging by its bubble level, lock the ball head

mechanism by turning the set screw clockwise with the 4 mm hex key until it is tightened. SR05 is now locked in its position.

A similar approach is followed when level ling SR05 on its tube mount in the field:

1) judge bubble level and cable orientatio n 2) loosen set screw to tilt and rotate SR05

3) tighten set screw to lock ball levelling 4) SR05 is mounted and levelled Figure 5.4.2 Levelling steps for SR05 when mounted on tube mount with ball levelling

SR05-D1A3-PV manual v1801 30/83

When retrofitting SR05 or when ordering SR05 pyr a nometer and its optional ball levelling in separate orders, the user has to ensure a shim is placed properly in the centre of the bottom plate of SR05. The shim allows smooth levelling. Read the following chapter on placing and removing the shim. When ordering SR05 combined with ball levelling, the shim is already positioned in its place in the factory.

5.5 Placing and removing SR05’s ball levelling shim

Only when ordering SR05 pyranometer and its optional ball levelling separately or when exchanging a SR05 se nsor on a ball levelling mount (retrofitting), the user has to ensure a dedicated shim is placed properly in the centre of the bottom plate of SR05. When ordering SR05 combined with ball levelling the shim is already positioned in its place in the factory. The aluminium shim ensures a secure fit between SR05 and ball levelling and allows the ball head to rotate smoothly for easy levelling. The shim, a loose set screw, a 4 mm hex key, two M5x20 mounting bolts and two M5 nuts are included when ordering the ball levelling mount separately.

Figure 5.5.1 Line drawing indicating placement of the aluminium shim and photo showing the shim properly positioned in the centre of SR05’s bottom plate. Note the position of the protruding ledge when placing the shim.

The shim can be placed into SR05’s bottom plate following thes e steps:

1) If your SR05 has a small black plastic cover cap on the countersunk set screw

opening on SR05’s side, remove it. A small flathead screwdriver may be used. Then insert the loose set screw with a 4 mm hex key by turning the hex key clockwise until the screw is only slightly protruding (sticking out).

2) Hold SR05 in one hand, the shim in the other.

3) Ensure the orientation of the shim fits with that of SR05’s bottom plate. Note the

position of the protruding ledge (see Figure 5.5.1).

SR05-D1A3-PV manual v1801 31/83

4) Pinch the shim slightly in order to reduce its diameter and to make it fit easily into

SR05’s bottom plate.

5) While pinching, push the shim into its position on SR05’s bottom plate.

The shim is placed. For mounting and levelling, continue with the following steps:

6) Mount the ball levelling with its mounting bolts.

7) SR05, with its shim positioned, can now be placed on the ball levelling mount.

Gently push the sensor ont o the ball head until it clicks.

8) The ball head can be rotated 360 ° and allows angle compensation on non-

horizontal surfaces up to 10 °.

9) When SR05 is mounted and levelled, judging by its bubble level, lock the ball head

mechanism by turning the set screw clockwise with a 4 mm hex key until it is tightened. The set screw should be countersunk a nd not protruding (not sticking out).

When the ball head is not inserted in SR05, the shim makes a minor rattling noise when moving SR05. This is normal, caused by mechanical freedom between the two parts.

The shim can be removed from SR05’s bottom plate by hand with the assistance of a small flathead screwdriver. See the chapter on tooling required. Let the screwdriver gently tip the shim out. When removing or placing the shim, make sure the glass dome is protected at all times.

SR05-D1A3-PV manual v1801 32/83

5.6 Electrical connection of SR05-D1A3-PV: wiring diagram

The instrument must be powered by an external power supply, providing an operating voltage in the range from 5 to 30 VDC. SR05-D1A3-PV offers irradiance in W/m

as a

digital output (Modbus over RS-485) and as an analogue 0 to 1 V output.

Table 5.6.1 Wiring diagram of SR05-D1A3-PV

PIN WIRE

SR05-D1A3-PV

Modbus over RS-485

SR05-D1A3-PV

0 to 1 V output

1 Brown VDC [+] VDC [+] 4 Black VDC [−] VDC [−] 3

Blue not connected 0 to 1 V output

2 White RS-485 B / B’ [+] not connected 5

Grey RS-485 A / A’ [−] not connected

Yellow shield shield

Note: at the connector-end of the cable, the shield is connected to the connector housing

5.7 Grounding and use of the shield

Grounding and shield use are the responsibility of the user. The cable shield (called shield in the wiring diagram) is connected to the aluminium instr ume nt body via the connector. In most situations, the instrument will be bolted on a mounting platform that is locally grounded. In these cases the shield at the cable end should not be connected at all. When a ground connection is not obtained through the instrument body, for instance in laboratory experiments, the shield should be connected to the local earth ground at the cable end. This is typically the ground or low voltage of the power supply or the common of the network. In exceptional cases, for instance when both the instrument and a datalogger are connected to a small size mast, the local ground at the mounting platform is the same as the network ground. In such cases ground connection may be made both to the instrument body and to the shield at the cable end.

SR05-D1A3-PV manual v1801 33/83

5.8 Using SR05-D1A3-PV’s digital output

SR05-D1A3-PV can be read out either via its digital output or via its analogue output. When opting for the analogue output, please refer to the next section. This section describes how to use the digital output. When using SR05’s d ig ital output, SR05-D1A3-PV can be connected to an RS-485 network. How to communicate with SR05, and the Modbus protocol, is described in chapter 6.

5.8.1 Connecting SR05-D1A3-PV to an RS-485 network

SR05-D1A3-PV is suited for a two-wire (half-duplex) RS-485 network. In such a network SR05-D1A3-PV acts as a slave, receiving data requests from the master. An example of the topology of an RS-485 two-wire network is shown in the figure below. SR05-D1A3-PV is powered from 5 to 30 VDC . The power supply is not shown in the figure. The V DC [-] power supply ground must be connected to the common line of the network.

Figure 5.8.1.1 Typical topology of a two-wire RS-485 network, figure adapted from: Modbus over serial line specification and implementation guide V1.02 (www.modbus.org). The power supply is not shown in this figure.

After the last nodes in the network, on both sides, line termination resistors (LT) are required to eliminate reflections in the network. According to the EIA/TIA-485 standard, these LT have a typical value of 120 to 150 Ω. Never place more than two LT on the network and never place the LT on a derivation cable. To keep the RS-485 bus in a well

5 V

Pull up

Pull down

Balanced pair

Common

RS-485 B/B’[+]

RS-485 A/A’[-]

SR05-D1A3-PV / Slave 1

Slave n

Master

( VDC[- ] )

SR05-D1A3-PV manual v1801 34/83

defined state when no transmiss io n is occurring, a pull up and pull down resistor are recommended. Typical values for both resistors are in the range from 650 to 850 Ω.

Figure 5.8.1.2 Connection of SR05-D1A3-PV to an RS-485 network. SR05-D1A3-PV is powered by an external power supply of 5 to 30 VDC.

shield

[+] 5 to 30 VDC

[-]5 to 30 VDC

common [+] data

[ -]data, RS-485 A / A’

SR05-D1A3-PV wire

black

grey

white

blue

yellow

brown

, RS-485 B / B’

RS-485 network

not connected

SR05-D1A3-PV manual v1801 35/83

5.8.2 Connecting SR05-D1A3-PV to a PC

SR05-D1A3-PV can be accessed vi a a PC. In that case communication with the sensor can be done via the user interface offered by the Sensor Manager software (see the next chapters) or by any other Modbus testing tool.

Depending on the available ports on the PC, either an RS-485 to USB converter or an RS485 to RS-232 converter is used. The figure below shows how connections are made. The converter must have galvanic isolation between signal input and output to prevent static electricity or other high-voltage surges to enter the data lines. An external power supply is required to power the SR05-D1A3-PV (5 to 30 VDC). An RS-485 to USB converter is usually powered via the USB interface in which case no external power is needed to feed the converter. If an RS-485 to RS-232 converter is used the converter may need an external power source. Thi s may be the same supply used for the SR05-D1A3-PV.

Figure 5.8.2.1 Connecting SR05-D1A3-PV to an RS-485 to USB converter and a PC

shield

[+] 5 to 30 VDC

[-]5 to 30 VDC

common [–] data

[

]

data

SR05-D1A3-PV wire

black

grey white

blue

yellow

brown

RS-485 / USB converter

not connected

USB to PC

SR05-D1A3-PV manual v1801 36/83

5.9 Using SR05-D1A3-PV’s analogue 0 to 1 V output

SR05-D1A3-PV gives users the option to use 0 to 1 V output instead of its digital output. This section explains how to use the 0 to 1 V output. When opting solely for SR05-D1A3-PV’s digital output, please refer to section 5.8.

Using the 0 to 1 V output provided by SR05-D1A3-PV is easy. The instrument can be connected directly to commonly used datalogging systems. The irradiance, E, in W/m

is calculated by measuring the SR05-D1A3-PV output, a voltage U, in V, and then multiplying by the transmitted range r. The transmitted range is provided with SR05-D1A3-PV on its product certificate. By convention 0 W/m

irradiance corresponds with 0 V transmitter output voltage. The transmitted range, which is the irradiance at output voltage of 1 V, and is typically 1600 W/m

. The transmitted range can be adjusted

at the factory upon request.

The central equation governing SR05-D1A3-PV is:

E = r·U (Formula 5.9.1)

The standard setting is: E = 1600·U. See chapter 5.5 and the diagram below for electrical connections to voltmeters, when using SR05-D1A3-PV’s 0 to 1 V output.

Figure 5.9.1 Electrical diagram of the connection of SR05-D1A3-PV to a typical voltmeter or datalogger with the capacity to measure voltage signals. SR05-D1A3-PV operates on a supply voltage of 5 to 30 VDC.

SR05-D1A3-PV

brown [+]

black blue 0 to 1 V output

ground

power supply 5 to 30 VDC

voltmeter

yellow

U = 0 - 1 VDC

SR05-D1A3-PV manual v1801 37/83

6 Communication with SR05

SR05-D1A3-PV has a Modbus output that is compatible with the IMT-Solar Si-RS485-TC-T-MB silicon reference cell: most of the Modbus functionality of the silicon reference cell is also supported by SR05-D1A3-PV. This mak es it easy to install SR05-D1A3-PV in existing photovoltaic monitoring systems without the need to make major modifications to the datalogging software or infrastructure.

In addition to the silicon reference cell compatible Modbus output, our standard Hukseflux Modbus registers are available with an offset in the register address.

6.1 PC communication: Sensor Manager software

The digital SR05 series can be accessed via a PC. In that case the communication with the sensor is done via the user interface offered by the Hukseflux Sensor Mana g e r software or by another Modbus testing tool. The Sensor Manager can be downloaded by the user via www.hukseflux.com/downloads. Alternatively, there are links to testing tools, paid or freeware, available at www.modbus.org. This chapter describes the functionality of the Sensor Manager only.

The Hukseflux Sensor Manager software provides a user interface for communication between a PC and SR05. It allows the user to locate, configure a nd test one or more SR05’s and to perform simple laboratory measurements using a PC. The Sensor Manager’s most common use is for initial functionality te sting and modification of the SR05 Modbus address and communication settings. It is not intended for long-term continuous measurement purposes. For available software updates of the Sensor Manager, please check www.hukseflux.com/downloads.

6.1.1 Installing the Sensor Manager

Running the Sensor Manager requires installation of the latest version of Java Runtime Environment s oft ware. Java Runtime Environment may be obtained free of charge from

www.java.com. The SR05 specifications overview (Table 3.1.1) shows the system and

software requirements for using a PC to communicate with SR05.

1) Download the Hukseflux Sensor Manager via www.hukseflux.com/downloads.

Unzip the downloaded files and copy the folder “Hukseflux Sensor Manager” to a folder on a PC. For proper installation the user should have writing rights for

this file location.

Double-click “Hukseflux_Sensor_Manager.jar” in the folder “Hukseflux Sensor

Manager”. This will start up the Sensor Manager.

SR05-D1A3-PV manual v1801 38/83

6.1.2 Trouble shooting during Sensor Manager installation

• When Java Runtime Environment software is not installed, a Windows message comes up, displaying “the file “Hukseflux_Sensor_Manager.jar” could not be opened”. The solution is to install Java Runtime E nvironment on the PC and try again. Sensor Manage r: main window

6.1.3 Sensor Manager: main window

Figure 6.1.3.1 Main window of the Sensor Manager.

When the Sensor Manager is started and a digital SR05 is connected to the PC, the user can communicate with the instrument.

In the “Sensor type” drop down box, select model “SR05-D1A3-PV”. In the “Serial communication settings” box, select the pyranometer’s BAUD rate, parity and data and stop bits. In the “Modbus address” field, key in the instrument’s Modbus

SR05-D1A3-PV manual v1801 39/83

address. Once the Modbus address is set, click “Connect” to establish contact with the instrument.

Note: the “Auto-detect Hukseflux” option in the “Sensor type” drop down box, the “Find First” button and the “Find All” button only work for standard Hukseflux sensors and will not work for model SR05-D1A3-PV.

Figure 6.1.3.2 Sensor Manager main window with two connected SR05’s. When an instrument is found, temperature and irradiance data are displayed. Updates

are done manually or automatically. Automatic updates can be made every second, every 5 seconds or every minute.

6.1.4 Sensor Manager: plotting data

When the “Plot on Live Chart” button in the lower right corner is clicked the “Plot window” opens. A live graph is shown of the measurement with the selected instrument. The x-axis, time, is scaled automatically to display data of the complete measurement period. After checking the box “Show tail only”, only the last minutes of measured data

SR05-D1A3-PV manual v1801 40/83

are displayed. When the “update interval” is 1 second, the “Show tail only” function is available after around 10 minutes of data collection. The y-axis displays the measured irradiance in W/m

. The Y-axis automatically scales to display the full measured range .

Figure 6.1.4.1 Example of an SR05 irradiance plot in the Sensor Manager.

6.1.5 Sensor Manager: information about the instrument

The main window shows the “Show details” button, giving access to the “Sensor details” window. This window displays calibration results and calibration history, temperature coefficients and other properties of the selected instrument, as shown on the next p age. The sensor serial number and all calibration information should match the information on the instrument label and on the product certificate.

SR05-D1A3-PV manual v1801 41/83

Figure 6.1.5.1 Sensor details window in the Sensor Manager.

6.1.6 Sensor Manager: changing Modbus address and communication settings

In the “Sensor details” window the “Change serial settings” function ope ns the “Change serial communication settings” window, as shown in the figure below.

SR05-D1A3-PV manual v1801 42/83

Figure 6.1.6.1 Change serial communication settings window in the Sensor Manager

When new communication settings or a new Modbus address are entered, these need to be confirmed by clicking “Change settings”. The instrument w ill then automatically restart. In case the “Change settings” function is not activated, the original settings remain valid. If the Modbus address is changed, the Sensor Manager will automatically reconnect with the instrument using the new address after restart.

6.1.7 Sensor Manager: adjustment of the sensitivity by power users

The Sensor Manager does not allow a “standard user” to change any settings that have a direct impact on the instrument output, i.e. the irradiance in W/m

. However, in case the instrument is recalibrated it is common practice that the sensitivity is adjusted, and that the latest result is added to the calibration history records. This can be done after obtaining a password and becoming a “power user”. Please contact the factory to obtain the password and to get directions to become a “power user”.

Example: During a calibration experiment, th e r esu lt might be that SR05 has an irradiance output in W/m

that is 990, whereas the standard indicates it should be 970.

The SR05 output is in this example 2.06 % too high. The original sensitivity of

16.15 x 10

-6

V/(W/m2) ought to be changed to 16.48, using registers 0x1029 + 0x102A. The old calibration result is recorded in the calibration history file. In case there are still older results these are moved over to higher register numbers 0x103F to 0x1051.

SR05-D1A3-PV manual v1801 43/83

6.2 Network communication: function codes, registers, coils

Warning: Using the same Modbus address for more than one device will lead to irregular behaviour of the entire network. This chapter describes function codes, data model and

registers used in the SR05-D1A3-PV firmware. Communication is organised according to the specifications provided by the Modbus Organization. These specifications are explained in the documents “Modbus application protocol v1.1b” and “Modbus over serial line v1.02”. These documents can be acquired free of charge at www.modbus.org.

Table 6.2.1 Supported Modbus function codes

SUPPORTED MODBUS FUNCTION CODES

FUNCTION 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 0x08 Diagnostics 0x0F Write Multiple Coils 0x10 Write Multiple Registers

0x46

Communication Parameter

Note: In accordance with the Modbus application protocol specification function codes 0x01 to 0x06, 0x08, 0x0F and 0x10 belong to the category of public function codes, whereas function code 0x46 belongs to the category of user defined function codes. User defined function codes are non standard. The usage of function code 0x46 is explained in detail in section 6.3.3.

Table 6.2.2 Modbus data model

MODBUS DATA MODEL

PRIMARY TABLES OBJECT TYPE TYPE OF

Discrete input Single bit R Coil Single bit R/W

Input register

16 bit word

Holding register 16 bit word R/W R = read only, W = write only, R/W = read / write

The instrument does not distinguish between discrete input and coil; neither between input register and holding register.

SR05-D1A3-PV manual v1801 44/83

Table 6.2.3 Format of data

FORMAT OF DATA

DESCRIPTION

U16 Unsigned 16 bit integer S16 Signed 16 bit integer U32 Unsigned 32 bit integer

S32

Signed 32 bit integer

Float IEEE 754 32 bit floating point format String A string of ASCII characters

The data format includes signed and unsigned integers. The difference between these types is that a signed integer passes on negative values, which reduces the range of the integer by half. Up to five 16 bit registers can be requested in one request; if requesting six or more registers, multiple requests should be used.

If the format of data is a signed or an unsigned 32 bit integer, the first register received is the most significant word (MSW) and the second register is the least significant word (LSW). This way two 16 bit registers are reserved for a 32 bit integer. If the format of data is float, it is a 32 bit floating point operator and two 16 bit registers are reserved as well. Most network managing programs have standard menus performing this type of conversion. In case manual conver sion is required, see the appendix on conversion of a floating point number to a decimal number. MSW a nd LSW should be read together in one request. This is necessary to make sure both registers contain the data of one internal voltage measurement. Reading out the registers with two different instructions may lead to the combination of LSW and MSW of two measurements at different points in time.

An Unsigned 32 bit integer can be calculated by the formula: (MSW x 2

)+LSW = U32. An example of such a calculation is available in the paragraph “Network communication: example master request to SR05”.

Your data request may need an offset of +1 for each SR05 register number, depending on processing by the network master. Exa m ple: SR05 register number 7 + master offset = 7 + 1 = master register number 8. Consult the manual of the device acting as the local master.

SR05-D1A3-PV manual v1801 45/83

6.3 Silicon Reference Cell compatible Modbus output

SR05-D1A3-PV has an IMT-Solar Si-RS485TC-T-MB silicon reference cell compatible Modbus output. The corresponding input registers, diagnostic function and serial communication settings are explained below.

6.3.1 Input registers (0x04)

Table 6.3.1.1 PV reference cell compatible input registers.

MODBUS REGISTERS 0x0000-0x0008

PARAMETER DESCRIPTION OF CONTENT TYPE

OF (R/W)

FORMAT OF DATA

0x0000 Irradiance (W/m2) Irradiance = value/10 R U16

0x0001

Cell temperature (°C)

Temperature = (value-250)/10

U16

0x0002 External temperature

(

Not available, always returns 0 R U16

0x0003 Wind speed (m/s) Not available, always returns 0 R U16 0x0004 Factory use only - - -

0x0005 Cell temperature (°C) Temperature = (value-1000)/10 R U16

0x0006

External temperature

(°C)

Not available, always returns 0

U16

0x0007 Cell temperature (°C) Temperature = value/10 R S16

0x0008

External temperature

(°C)

Not available, always returns 0

S16

6.3.2 Diagnostics (0x08)

Diagnostic subfunction codes supported by SR05-D1A3-PV are listed in Table 6.3.2.1

Table 6.3.2.1 Diagnostic subfunction codes supported by SR05-D1A3-PV

DIAGNOSTIC SUBFUNCTION CODES

SUB FUNCTION

CODE

NAME DATA COMMENT

0x0000

Return query data

Any

0x0001 Restart communications

option

0x0000 or

0xFF00

0x0004

Force listen only mode

0x0000

0x000A

Clear counters

0x0000

0x000B Bus message count 0x0000 Only counts messages for this

device

0x000C

Checksum error count

0x0000

0x000D

Error exception count

0x0000

0x000E

Slave message count

0x0000

0x000F

Slave no response co unt

0x0000

Not available, always returns 0

0x0010

Slave NAK count

0x0000

Not available, always returns 0

0x0011

Slave busy count

0x0000

Not available, always returns 0

0x0012

Bus overrun count

0x0000

SR05-D1A3-PV manual v1801 46/83

6.3.3 Serial communication settings (0x46)

Function code 0x46 allows the user to set the device address and to read and write the serial settings. This section gives a description of the usage of function code 0x46 with sub function codes 0x04, 0x05 and 0x06.

Sub function 0x04: write device address Sub function code 0x04 is used to change the device addres s. Upon sending the Modbus request SR05-D1A3-PV will echo the Modbus request. Note that the new device address will only take effect after the device has been reset (see diagnostic function code 0x08, sub function 0x01).

Modbus request:

Device address

1 Byte

1 to 247

Function code

1 Byte

0x46

Sub function code

1 Byte

0x04

New device address

1 Byte

1 to 247

Checksum

2 Byte

CRC16

Device address

1 Byte

1 to 247

Function code

1 Byte

0x46

Sub function code

1 Byte

0x04

New device address

1 Byte

1 to 247

Checksum

2 Byte

CRC16

Sub function 0x05: read serial communication settings Sub function code 0x05 is used to read the serial communication settings such as the baud rate and the bit frame.

Modbus request:

Device address

1 Byte

1 to 247

Function code

1 Byte

0x46

Sub function code

1 Byte

0x05

Checksum

2 Byte

CRC16

Device address

1 Byte

1 to 247

Function code

1 Byte

0x46

Sub function code

1 Byte

0x05

Baud rate

1 Byte

0 to 4, see table 6.3.3.1

Bit frame

1 Byte

0 to 3, see table 6.3.3.2

Checksum

2 Byte

CRC16

Subfunction 0x06: write serial communication settings Sub function code 0x06 is used to write the serial communication settings such as the baud rate and the bit frame. Upon sending the Modbus re quest SR05-D1A3-PV will echo the Modbus request. Note that the new serial communication settings will only take effect after the device has been reset (see diagnostic function code 0x08, sub function 0x01).

SR05-D1A3-PV manual v1801 47/83

Modbus request:

Device address

1 Byte

1 to 247

Function code

1 Byte

0x46

Sub function code

1 Byte

0x06

Baud rate

1 Byte

0 to 4, see tab le 6. 3. 3.1

Bit frame

1 Byte

0 to 3, see table 6.3.3.2

Checksum

2 Byte

CRC16

Reply:

Device address

1 Byte

1 to 247

Function code

1 Byte

0x46

Sub function code

1 Byte

0x05

Baud rate

1 Byte

0 to 4, see tab le 6. 3. 3.1

Bit frame

1 Byte

0 to 3, see table 6.3.3.2

Checksum

2 Byte

CRC16

Table 6.3.3.1 Baud rate values for function code 0x46, sub function code 0x05 and 0x06

COMMUNICATION SETTINGS: BAUD RATES

Value Baud rate

1200

1 2400

9600

3 19200

38400

Table 6.3.3.2

Bit frame values for function code 0x46, sub function code 0x05 and 0x06

COMMUNICATION SETTINGS: BIT FRAME

Value Bit frame (data bits/parity bits/stop bits)

0 8N1

8N2

2 8E1 3 8O1

SR05-D1A3-PV manual v1801 48/83

6.4 Standard Hukseflux Modbus Output

In addition to the IMT-Solar Si-RS485TC-T-MB silicon reference cell compatible Modbus output, SR05-D1A3-PV supports the standard Hukseflux Mo db us output, but with an offset of 0x1000 in the register address as compared to SR05-D1A3:

SR05-D1A3-PV register address = SR05-D1A3 register address + 0x1000

Table 6.4.1 Modbus registers 0x1000 to 0x100B. For basic operation, Hukseflux recommends to read out registers 0x1002 + 0x1003 for solar radiation, register 0x1006 for instrument body temperature and register 0x1028 for the sensor serial number.

MODBUS REGISTERS 0x1000-0x100B

PARAMETER DESCRIPTION OF CONTENT TYPE

OF (R/W)

FORMAT OF DATA

0x1000

Modbus address

Sensor address in Modbus

network, default = 1

R/W

U16

0x1001 Serial communication

settings

Sets the serial communication, default = 5

R/W U16

0x1002 + 0x1003

Irradiance

signal in x 0.01 W/m² R S32

0x1004 + 0x1005

Factory use only

0x1006 Sensor body

temperature

In x 0.01 °C R S16

0x1007

Sensor electrical

resistance

In x 0.1 Ω

U16

0x1008 Scaling factor

irradiance

Default = 100 R U16

0x1009

Scaling factor

temperature

Default = 100

U16

0x100A + 0x100B

Sensor voltage output In x 10-9 V R S32

0x100C to

0X101F

Factory use only

Register 0x1000, Modbus address, contains the Modbus address of the sensor. This allows the Modbus master to detect the slave, SR05-D1A3-PV, in its network. The address can be changed; the value of the address must be between 1 and 247. The default Modbus address is 1. Note: The sensor needs to be restarted before changes become effective.

Register 0x1001, Serial communication settings, is used to enter the settings for baud rate and the framing of the serial data transfer. Default setting is setting number 5: 19200 baud, 8 data bits, even parity and 1 stop bit. Setting options are shown in the table below. Note: The sensor needs to be restarted before changes become effective.

SR05-D1A3-PV manual v1801 49/83

Table 6.4.2 Serial communication setting options of register 0x1001

SETTING OPTIONS

SETTING NUMBER

BAUD RATE DATABITS STOPBITS PARITY

9600

8 1 none

9600

8 1 even

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 115200 8 1 odd 13 1200 8 1 none 14 1200 8 1 even

1200

8 1 odd

16 2400 8 1 none 17 2400 8 1 even 18 2400 8 1 odd 19 9600 8 2 none 22 19200 8 2 none

38400

8 2 none

28 115200 8 2 none

1200

8 2 none

34 2400 8 2 none

Register 0x1002 + 0x1003, Irradiance, provides the solar radiation output in 0.01 W/m². The value given must be divided by 100 to get the value in W/m². MSW and LSW should be read together in one request.

Register 0x1006, Instrument body temperature, provides the temperature of the instrument body in 0.01 °C. The data must be divided by 100 to achieve the value in °C.

Register 0x1007, Sen sor electrical r esistance, sensor resistance in 0.1 Ω. The data needs to be divided by 10 to get the value in Ω. This register returns a 0 by default. To read the resistance, first a measurement has to be performed. This can be done by writing 0xFF00 to coil 2. Hukseflux recommends to use this function only when necessary for diagnostics in case of sensor failure.

SR05-D1A3-PV manual v1801 50/83

-9

Table 6.4.3 Modbus registers 0x1020 to 0x103E, sensor and calibration information

MODBUS REGISTERS 0x1020-0x103E

PARAMETER DESCRIPTION OF CONTENT TYPE

OF (R/W)

FORMAT OF DATA

0x1020 to 0x1023

Sensor model Part one of sensor

description

R String

0x1024 to

0x1027

Sensor model

Part two of sensor

description

String

0x1028 Sensor serial number R U16

0x1029 +

0x102A

Sensor sensit ivity

In x 10

-6

V/(W/m2)

Float

0x102B Response time In x 0.1 s R U16

0x102C

Sensor resistance

In x 0.1 Ω

U16

0x102D Reserved Always 0 R U16

0x102E +

0x102F

Sensor calib rat ion

date

Calibration date of the

sensor in YYYYMMDD

U32

0x1030 to 0x103C

Factory use

0x103D

Firmware version

R U16

0x103E Hardware version R U16

Registers 0x1020 to 0x1027, Sensor model, String of 16 characters. There are 8 registers with two ASCII encoded characters per register containing the sensor model name. The decoding is explained in Appendix 9.12 of this manual.

-6

V/(W/m²). Format of data is float.

Register 0x102B, Response time, the response time of the sensor as measured in the factory in x 0.1 s. The value must be divided by 10 to get the value in s.

Register 0x102C, Sensor electrical resistance, returns the electrical resistance measured during the sensor calibration. The resistance is in x 0.1 Ω and must be divided by 10 to get the value in Ω.

Register 0x102E + 0x102F, Sensor calibration date, last sensor calibration date, from which the sensitivity in register 41 and 42 was found, in YYYYMMDD.

SR05-D1A3-PV manual v1801 51/83

Table 6.4.4 Modbus registers 0x103F to 0x1052, calibration history

MODBUS REGISTERS 0x103F-0x1052

PARAMETER DESCRIPTION OF

CONTENT

TYPE OF (R/W)

FORMAT OF DATA

0x103F + 0x1040

Sensor sensitivity history 1 In x 10

-6

V/(W/m2)

Default value is 0

R Float

0x1041 +

0x1042

Calibra tio n date h isto ry 1

Former calibration date of

the sensor in YYYYMMDD Default value is 0

U32

0x1043 + 0x1044

Sensor sensitivity history 2 See register 0x103F +

0x1040

R Float

0x1045 +

0x1046

Calibra tio n date h isto ry 2

See register 0x1041 +

0x1042

U32

0x1047 + 0x1048

Sensor sensitivity history 3 See register 0x103F +

0x1040

R Float

0x1049 +

0x104A

Calibra tio n date h isto ry 3

See register 0x1041 +

0x1042

U32

0x104B + 0x104C

Sensor sensitivity history 4 See register 0x103F +

0x1040

R Float

0x104D + 0x104E

Calibra tio n date h isto ry 4 See register 0x1041 +

0x1042

R U32

0x104F +

0x1050

Sensor sensitivity history 5

See register 0x103F +

0x1040

Float

0x1051 + 0x1052

Calibra tio n date h isto ry 5 See register 0x1041 +

0x1042

R U32

Register 0x103F to 0x1052: Only accessible for writing by Sensor Manager power users: power users can write calibration history to registers 0x103F to 0x1052. If default values are returned, no re-calibration has been written. Last calibration sensitivity and calibration date are available in register 0x1029 + 0x102A and 0x102E + 0x102F respectively.

Please note that if your data request needs an offset of +1 for each SR05 register number, depending on processing by the network master, this offset applies to coils as well. Consult the manual of the device acting as the local master.

SR05-D1A3-PV manual v1801 52/83

Table 6.4.5 Coils

COILS

COIL

PARAMETER

DESCRIPTION

TYPE OF

OBJECT TYPE

0 Restart Restart the sensor W Single bit

Reserved

2 Check Measure sensor

electrical resistance

W Single bit

Coil 0, Restart, when 0xFF00 is written to this coil the sensor will restart. If applied, a new Modbus address or new serial settings will become effective.

Coil 2, Check, when 0xFF00 is written to this coil the internal electronics will measure the electrical resistance of the thermopile. After the measurement, a new value will be written into register 7. Requesting to write this coil with a high repetition rate will result in irregular behaviour of the sensor; the check must be executed as an exceptional diagnostics routine only.

SR05-D1A3-PV manual v1801 53/83

6.5 Network communication: getting started

Once it has the correct Modbus address and communication settings, SR05-D1A3-PV can be connected directly to an RS-485 network and a power supply. How to physically connect a sensor as a slave in a Modbus network is shown in section 5.11: Connecting a SR05-D1A3-PV to an RS-485 network. In such a connection the sensor is powered via an external power supply of 5 to 30 VDC. When the sensor is bolted onto a grounded mounting plate, which is usually the case, the shield is no t connected to ground at the cable end.

Installing a SR05-D1A3-PV in the network also requi res c on figuring the communication for this new Modbus device. This usually consists of defining a request that can be broadcast by the master. If the SR05-D1A3-PV is not already defined as a standard sensor type on the network, contact the supplier of the network equipment to see if a library file for the SR05-D1A3-PV is available.

Typical operation requires the master to make a req u est of irradiance data in registers 0x1002 + 0x1003, sensor temperature in register 0x1006, and the sensor serial number in register 0x1028 every 1 second, and store the 60 second averages. The data format of register 0x1002 + 0x1003 is a signed 32 bit integer and the temperature in register 0x1006 is a signed 16 bit integer.

Up to five 16 bit registers can be requested in one request. In case six or more registers are requested in just one request, SR05-D1A3-PV will not respond. If requesting six or more registers, multiple requests should be used: SR05-D1A3-PV will respond as expected.

6.5.1 Adapting Modbus address and communication settings

Setting the instrument address and baud rate can be done in different ways:

• by connecting the sensor to the PC and using the Sensor Manager;

• by connecting the sensor to the PC and using another Modbus testing tool. There are

links to differe nt solutions available at www.modbus.org

;

• by using the available network user interfac e s o ft w ar e.

The Modbus address is stored in register 0x1000 and has a default value of 1. A user may change the address to a v alue in the range of 1 to 247. The address value must be unique in the network. The communication settings are stored in register 0x1001. The default setting is setting number 1 representing a communication with 9600 baud, no parity bit, 8 data bits and 1 stop bit. After a new address or communication setting is written the sensor must be restarted. This can be done by writing 0XFF00 to coil 0.

SR05-D1A3-PV manual v1801 54/83

6.6 Network communication: example master request to SR05

Normal sensor operation consists of requesting the output of registers 0x1002 + 0x1003; the temperature compensated solar radiation. For quality assurance also the sensor serial number, register 0x1028 and the temperature in register 0x1006, are useful.

In this example a SR05-D1A3-PV has address 64. The example requests the solar radiation (temperature com pensated) register 0x1002 + 0x1003, sensor serial number, register 0x1028, and the temperature of the instrument register 0x1006. The values are represented in hexadecimals.

Note: 32 bit data are represented in 2 registers. MSW and LSW should be read together in one request.

Request for sola r rad iation, regi st er 2 + 3:

Master Request: 0x40 0x03 0x1000 0x0004 0x4FD8

0x40 = Modbus slave address, decimal equivalent = 6 4 0x03 = Modbus function code: 0x03 Read holding registers

0x1000 = Starting register, the master requests data starting from register

0x1000. 0x0004 = Length, the number of registers the master wants to read. 4 registers 0x4FD8 = CRC, the checksum of the transmitted data

Sensor respon se: 0x40 0x03 0x08 0x0040 0x0005 0x0001 0x7C4F 0x79DA

0x40 = Modbus slave address, decimal equivalent = 64 0x03 = Modbus function 0x08 = Number of bytes returned by the sensor. 8 bytes transmitted by the sensor 0x0040 = Register 0x1000; Modbus address

0x0005 = Register 0x1001; Serial settings, 19200 baud, 8 data bits, even parity bit, 1 stop bit 0x0001 = Register 0x1002; Temperature compensated signal, Most Significant Word (MSW). Decimal equivalent = 1 0x7C4F = Register 0x1003; Temperature compensated signal, Least Significant Word (LSW) = Decimal equivalent = 31823 0x79DA = CRC, the checksum of the transmitted data

Together, register 0x1002 and 0x1003 are representing the temperature compensated solar radiation output measured by the SR05-D1A3-PV. The MSW is in register 0x1002 and the LSW in 0x1003. The output has to be calculated by the formula: ((MSW x 2

) + LSW)/100. In this example the result is: ((216 x 1) +

31823)/100 = 973.59 W/m²

SR05-D1A3-PV manual v1801 55/83

Request for body temperature, register 0x1006:

Master Request: 0x40 0x03 0x1006 0x0001 0x6FDA

0x40 = Modbus Slave address 0x03 = Modbus function 0x1006 = Start register 0x0001 = Number of registers 0x6FDA = CRC

Sensor respon se: 0x40 0x03 0x02 0x08B1 0x43FF

0x40 = Modbus Slave address 0x03 = Modbus function 0x02 = Number of bytes 0x08B1 = Content of register 0x1006, decimal equivalent = 2225 0x43FF = CRC

Temperature = Register 0x1006 x 0.01 = 2225 x 0.01 = 22.25 °C

Register 0x1006 represents the sensors body temperature. The received data needs to be divided by 100 to represent the correct outcome. In this exa mp le the result is: 2225 x 0.01 = 22.25 °C

Request for seri a l number, register 0x1028:

Master Request: 0x40 0x03 0x1028 0x0001 0x0FD3

0x40 = Modbus slave address 0x30 = Modbus function 0x1028 = Start register 0x0001 = Number of registers 0x0FD3 = CRC

Sensor respon se: 0x40 0x03 0x02 0x0A 0x29 0x43 0x35

0x40 = Modbus Slave address 0x03 = Modbus function 0x02 = Number of bytes 0x0A29 = Content of register 40, decimal equivalent = 2601 0x4335 = CRC

SR05-D1A3-PV manual v1801 56/83

7 Making a dependable measurement

7.1 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 requiremen t s 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 to repair)

It is important to realise that the uncertainty of the measurement is not only determined by the instrument but also by the way it is used.

See also ISO 9060 note 5. In case of pyranometers, the measurement uncertainty as obtained during outdoor measurements is a function o f:

• the instrument class

• the calibration procedure / uncertainty

• the duration of instrument employment under natural sunlight (involving the

instrument stability specification)

• the measurement cond itions (such as tilting, ventilation, shading, instr ume nt temperature)

• maintenance (mainly fouling)

• the environmental co nd itions*

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 at Hukseflux as all factors outside the instrument that are relevant to the measurement such as the cloud cover (presence or absence of direct radiation), sun position, the local horizon (which may be obstructed) or condition of the ground (when tilted). The environmental condition s also involve the question whether or not the measurement at the location of measurement is representative of the quantity that should be measured.

SR05-D1A3-PV manual v1801 57/83

7.2 Reliability of the measurement

A measurement is reliable if it measures within required uncertainty limits for most of the time. 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 relia bility 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 account measurement conditions and environmental conditions, the user will select an instrument of a certain class, and define maintenance support procedures.

In many situations the re is a limit to a realistically attaina ble accuracy level. This is due to conditions that are beyond control once the measurement system is in place. Typical limiting conditions are:

• the measurement conditions, for instance when working at extreme temperatures when the instrument temperature is at the extre m e lim its of the rated temperature range.

• the environmental conditions, for instance when installed at a sub-optimal measurement location with obstacles in the path of the sun.

• other environmental conditions, for instance when assessing PV system performance and the system contains panels at different tilt angles, the pyranometer measurement 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 undefined measurement uncertainty (sensitivity and directional error are no longer defined). This should be solve d 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, the uncertainty of the sensitivity gradually will increase. This is solved by regular recalibration.

• moisture condensing under pyranometer domes resulting in a slow change of sensitivity (within specifications). This is solved by regular replacement of desiccant or by maintenance (drying the entire sensor) in case the sensor allows this. For nonserviceable sensors like most second class pyranometers, this may slowly develop into a defect. For first class and secondary standard models (for instance model SR11 first class pyranometer and SR20-D2 digital secondary standard pyranometer) extra desiccant (in a set of 5 bags in an air tight bag) is available.

SR05-D1A3-PV manual v1801 58/83

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

• the use of redundant instruments allows remote checks of one instrument using the other as a reference, which leads to a higher measurement reliability.

• in PV system performance monitoring, in addition to instruments measuring in the plane of array, horizontally placed instruments are used for the measurement of global radiation. Global irradiance data enable the user to compare the local climate and system efficiency between different sites. These data can also be compared to measurements by local meteorological stations.

7.3 Speed of 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 the dependability.

Hukseflux pyranometers are designed to allow easy maintenance and rep air. The main maintenance actions are:

• replacement of desiccant

• replacement of cabling

For optimisation of dependability a user should:

• design a schedule of regular maintenance

• design 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 during service, recalibrations and repair.

7.4 Uncertainty evaluation

The uncertainty of a mea surement under outdoor or indoor conditions depends on many factors, see paragraph 1 of this chapter. It is not possible to give one figure for pyranometer measurement uncertainty. The work on uncertainty evaluation is “in progress”. There are several groups around the world participating in standardisation of the method of calculation. The effort aims to work according to the guidelines for uncertainty evaluation (according to the “G uide to Expression of Uncertainty in Measurement” or GUM).

SR05-D1A3-PV manual v1801 59/83

7.4.1 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 spe cifications of the instrument according to the list of ISO 9060 classification of

pyranometers and pyrheliometers are entered as limiting values of possible errors, to be analysed as type B evaluation of standar d uncerta inty 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 are entered 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) or in 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 incidenc e of direct radiation is a major factor in the uncertainty.

6) In uncertainty analysis for modern pyrheliometers: tilt dependence often is so low that

one single typical observatio n may be sufficient.

7) In cas e 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 covariance matrix are zero. Paragraph 5.1 of GUM.

10) Among the various sources of uncertainty, some are “not included in analysis”; this

applies for instance to non-linearity for pyranometers, because it is already included in the directional error, and the spectral response for pyranometers and pyrheliometers because it is already taken into account in the calibration process.

SR05-D1A3-PV manual v1801 60/83

Table 7.4.1.1 Preliminary estimates of achievable uncertainties of measurements with Hukseflux pyranometers. The estimates are based on typical pyranometer properties and calibration uncertainty, for sunny, clear sky days a nd well maintained stations, without uncertainty loss due to lack of 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 uncer t ainty evaluation of pyranometer measurements, so this table should not be used as a formal reference.

Pyranometer class (ISO 9060)

season latitude uncertainty

minute totals at solar noon

uncertainty hourly totals at solar noon

uncertainty daily totals

secondary standard

summer

mid-latitude

2.7 %

2.0 %

1.9 %

equator

2.6 %

1.9 %

1.7 %

pole

7.9 %

5.6 %

4.5 %

winter

mid-latitude

3.4 %

2.5 %

2.7 %

first class

summer

mid-latitude

4.7 %

3.3 %

3.4 %

equator

4.4 %

3.1 %

2.9 %

pole

16.1%

11.4 %

9.2 %

winter

mid-latitude

6.5 %

4.5 %

5.2 %

second class

summer

mid-latitude

8.4 %

5.9 %

6.2 %

(SR05 series)

equator

7.8 %

5.5 %

5.3 %

pole

29.5 %

21.6 %

18.0 %

winter

mid-latitude

11.4 %

8.1 %

9.9 %

7.4.2 Calibration uncertainty

New calibration procedures were developed in close cooperation with PMOD Worl d Radiation Center in Davos, Switzerland. The latest calibration method results in an uncertainty of the sensitivity of less than 1.8 %, compared to typical uncertainties of higher than 3.5 % for this pyranometer class. See the appendix for detailed information on calib ration hierarchy.

SR05-D1A3-PV manual v1801 61/83

8 Maintenance and trouble shooting

8.1 Recommended maintenance and quality assurance

SR05 can measure reliably at a low level of maintenance in most locations. Usually unreliable measurements will be detected as unreasonably large or small measured values. As a general rule this means that regular visual inspection combined with a critical review of the measured data, preferably checking against other measurements, is the preferred way to obtain a reliable measurement.

Table 8.1.1 Recommended maintenance of SR05. If possible the data analysis and cleaning (1 and 2) should be done on a daily basis. (continued on next page)

MINIMUM RECOMMENDED PYRANOMETER MAINTENANCE

INTERVAL

SUBJECT

ACTION

1 1 week data analysis compare measured data to maximum possible / maximum

expected irradiance and to other measurements nearby (redundant instruments). Also historical seasonal records can be used as a source for expected values. Analyse night time signals. These signals may be negative (dow n to - 5 W/m

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 from what is normal or expected

2 weeks

cleaning

use a soft cloth to clea n the dome of the instrument,

persistent stains can be treated with soapy water or a lcohol

3 6 months inspection inspect cable quality, inspect connectors, in s p ec t mounting

position, inspect cable, clean instrument, clean cable, inspect levelling, change instrument tilt in case this is out of specification, inspect mounting connection, inspect interior of dome for condensation

4 2 years desiccant

replacement

desiccant is specified to last for minimum 2 years. In case the user wants to replace desiccant himself, this is at own risk an d should only be executed in an ESD-safe work environment. The bottom plate of SR05 should be removed by unscrewing 3 x T10 screws with a Torx 10 screwdriver. The desiccant bag is taped on the bottom plate of SR05. Care should be taken when mounting th e b ottom plate on SR05

5 2 years recalibration recalibration by side-by-side comparison to a higher standard

instrument in th e field according to ISO 9847 request “power user” statu s an d a password at the factory permitting to write to registers holding the sensitivity and the calibration histor y data via the Sensor Manager

6 lifetime

assessment

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

SR05-D1A3-PV manual v1801 62/83

8.2 Trouble shooting

Table 8.2.1 Trouble shooting for SR05 (continued on next page)

General

Inspect 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 receiv es D C voltage power in the range of 5 to 30 VDC. Inspect the connection of the shield (typically not c onnected at the network side) . Inspect the connection of the sensor power supply, typically the negative is connected to the netw ork common.

Prepare for

indoor testing

Install the Sensor Manager software on a PC. Equip the PC with RS-485 for

communication with SR05-D1A3-PV. Put DC voltage power to the sensor and establish commun ic ation with the sensor. At power–up the signal may have a temporary outpu t level different from zero; an offset. Let this offset settle down.

The sensor does not give any signal

Check if the sens or reacts to light: expose the sensor to a strong light source, for instance a 100 W light bulb at 0.1 m distance. The signal should read > 100 W/m

now. Darken the s e nsor either by putting something over it or switching off the light. The instrument voltage output should go down a nd within one minute approach 0 W/m

. Check the data acquisition by replacing the sensor with a spare

sensor with the same address.

Not able to communicate with the sensor

Check all physica l connections to the sensor and try connecting to the sensor again. If commu nicating is not possible, try to figu r e out if the address and communication settings are correct. Analyse the cable per formance by measuring resistance from pins to cable ends. The electrical resistance should be < 10 Ω. In case of doubt, try a new cable. Connect sensor to a PC and perform the “Find” and “Find all” operation with the Sensor Manager to locate the sensor and verify the communication settings. If all physical conne c tions are correct, and the sensor still cannot be found, please contact the factory to send the sensor to the manufacturer for diagnosis and service.

SR05 does not

respond to a request for 6 or more registers

It is not possible to request more than five 16 bit registers in one request. In case

of requesting six or more registers in just one request, the sensor will not respond. If requesting six or more registers, use multiple r e quests: the sensor will respond as expected.

The sensor

signal is unrealistically

Note that night-time signals may be negative (down to -5 W/m2 on clear windless

nights), due to zer o offset a. Check if the pyranometer ha s a clean dome.

MINIMUM RECOMMENDED PYRANOMETER MAINTENANCE (continued)

7 6 years parts

replacement

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

8 internal

inspection

if applicable: open instrument and inspect / replace O-rings; dry internal cav ity around the circuit board

9 recalibration

high-accuracy recalibration indoors according to ISO 9847 or

outdoors accordin g to ISO 9846

SR05-D1A3-PV manual v1801 63/83

high or low Check the location of the pyranometer; are th er e a ny obstructions that could

explain the measurement result. Check the orientation / levelling of the pyranometer. Check the cable condition looking for cable breaks. Check the condition of the connectors (on chassis as well as the cable).

The sensor signal shows unexpected variations

Check the presence of strong sources of electromagnetic radiation (radar, ra dio). 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 dome

shows internal condensation

Arrange to send the sensor back to Hukseflux for diagnosis.

8.3 Calibration and checks in the field

Recalibration of field pyranometers is typically done by comparison in the field to a reference pyranometer. The applicable standard is ISO 9847 “International StandardSolar Energy- calibration of field 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 by comparison to an identical reference instrument, under normal incidence conditions.

The recommended calibration interval of pyranometers is 2 years. The registers containing the applied sensitivity and the ca libra tion history of SR05 are accessible for users. 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. Request “power user” status and a password at the factory permitting to write to registers holding the sensitivity and the calibration history data via the Sensor Manager.

In case of field comparison; ISO recommends field calib ration to a higher class pyranometer. Hukseflux suggests also allowing use of sensors of the same model and class, because intercomparisons of similar instruments have the advantage that they suffer from the same offsets. It is therefore just as good to compare to pyranometers of the same brand and type as to compare to an instrument of a higher class. ISO recommends to perform field calibration during several days; 2 to 3 days under c loudless conditions, 10 days un d er cloudy conditions. In general this is not achievable. In order to shorten the calibration process Hukseflux suggests to allow calibration at normal incidence, using hourly totals near solar noon.

SR05-D1A3-PV manual v1801 64/83

Hukseflux main recommendations for field intercomparisons are:

1) to take normal incidence as a reference and not the entire day.

2) to take a reference of the same brand and type as the field pyranometer or a pyranometer of a higher class, and

3) to connect both to the same electronics, so that electronics errors (also offsets) are eliminated.

4) to mount all instruments on the same platform, so that they have the same body temperature.

5) assuming that the electronics are indepe ndent ly c alibrated, to analyse radiation values at normal incidence radiation (possibly tilting the radiometers to approximately normal incidence), if this is not possible to compare 1 hour totals around solar noon for horizontally mounted in struments.

6) for second class radiometers, to c o rr ect deviations of more than ± 10 %. Lower deviations should be interpreted as acceptable and should not lead to a revised sensitivity.

7) for first class 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 secondary standard instruments, to correct deviations of more than ± 3 %. Lower deviations should be interpreted as acceptable and should not lead to a revised sensitivity.

8.4 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

• analysis of night time signals

The main idea is that one should look out for any unrealistic values. There are programs on the market that can semi-automatically perform data screening. See for more information on such a program: www.dqms.com.

SR05-D1A3-PV manual v1801 65/83

SR05-D1A3-PV manual v1801 66/83

9 Appendices

9.1 Appendix on cable extension / replacement

The sensor cable of the SR05 series is equipped with a M12-A straight connector. In case of cable replacement, it is recommended to purchase a new cable with connector at Hukseflux. In case of cable extension, it is recommended to purchase an extension cable with connector pairs at Hukseflux. Please note that Hukseflux does not provide support for Do-It-Yourself connector and cable assembly.

SR05 is equipped with one cable. Maximum length of the sensor cable is recommended to be 40 metres. It is good practice to keep the length of the instrument as short as possible to avoid inference of the signal and keep noise at acceptable levels.

Do not use SR05’s original factory-made cables with a total length of mo re than 40 metres.

Connector and cable specifications are summarised on the next page.

Figure 9.1.1 On the left the SR05 cable with M12-A female connector on sensor end. The cable is non-stripped on the other end. Its length is 3 metres standard and available in 10 and 20 metres too. On the right Hukseflux extension cable with connector pairs, with male and female M12-A connectors, available in 10 and 20 metres.

SR05-D1A3-PV manual v1801 67/83

Table 9.1.1 Specifications for SR05 cable replacement and extension

General replacement

please order a new cable with connector at Hukseflux

General cable extension please order an extension c a b le with connector pairs at Hukseflux

Connectors used

chassis: M12-A straight male conn ector, male thread, 5-pole manufacturer: Binder cable: M12-A straight female connector, female thread, 5-pole manufacturer: Binder The shield is electrically con nected to the connector housing

Cable

5-wire, shielded manufacturer: Binder

Length

cables should be kept as short as possible; total cable length should be less than 40 m

Outer sheath

with specificati ons for outdoor use (for good stability in outdoor applications)

SR05-D1A3-PV manual v1801 68/83

9.2 Appendix on tools for SR05

Table 9.2.1 Specifications of tools for SR05

CONFIGURATION

TOOLS INCLUDED

tooling required for mounting SR05 without ball levelling

two M5 bolts applicable screwdriver

no no

tooling required for mounting SR05 with ball levelling

hex key 4 mm wrench size 8 mm for M5 nuts

yes no

tooling required for mounting SR05 with tube mount

hex key 4 mm

yes

tooling required for levelling SR05 with ball levelling a nd tube mount

hex key 4 mm

yes

tooling required for tipping the aluminium shim out of SR05’s bottom panel position

screwdriver blade width 2 to 4 mm

9.3 Appendix on spare parts for SR05

• SR05 cable with female M12-A connector on sensor end, non-stripped on other end (3, 10, 20 m). Specify cable length

• SR05 extension cable w ith c onnector pair, with male and female M12-A connectors, (10, 20 m). Specify extension cable length

• Ball levelling (order number BL01)

• Tube mount (order number TM01)

• Tube mount with ball levelling (order number TMBL01)

• Shim for ball levelling mount

• Countersunk set screw for ball levelling mount

• 2 x M5x40 mounting bolts

• 2 x M5x30 mounting bolts

• 2 x M5x20 mounting bolts with 2 x M5 nuts

• Desiccant (silica gel, 1.0 g, in a HDPE bag)

NOTE: Dome, bubble level and sensor of SR05 cannot be supplied as spare parts

SR05-D1A3-PV manual v1801 69/83

9.4 Appendix on standards for classification and calibration

Both ISO and ASTM have standards on instrument classification and m ethods of calibration. The World Meteorologica l Organisation (WMO) has largely adopted the ISO classification system.

Table 9.4.1 Pyranometer standardisation in ISO and ASTM.

STANDARDS ON INSTRUMENT CLASSIFICATION AND CALIBRATION

ISO STANDARD

EQUIVALENT ASTM STANDARD

ISO 9060:1990 Solar energy -- Specification and classification of instruments for measuring hemispherical so lar and direct solar radiation

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

Comment: a standard “Solar energy --Methods for testing pyranometer an d pyrheliometer characteristics” has been announced in ISO 9060 but is not yet implemented.

not available

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

ASTM G167 - 05 Standa r d T est Method for Calibration of a Pyranometer Using a Pyrheliometer

ISO 9847:1992 Solar energy -- Calibration of field pyranometer s by comparison to a reference pyranometer

ASTM E 824 -10 Standard Test Method for Transfer of Calibration from Reference to Field Radiometers

ASTM G207 - 11 Standa r d T es t M ethod for Indoor Transfer of Calibration from Reference to Field Pyranometers

ISO 9059:1990 Solar energy -- Calibration of field pyrheliome te r s b y comparison to a reference pyrheliometer

ASTM E 816 Standard Test Meth od f or Calibration of Pyrheliometers by Comparison to Reference Pyrheliometers

SR05-D1A3-PV manual v1801 70/83

9.5 Appendix on calibration hierarchy

The World Radiometric Reference (WRR) is the measurement standard representing the Sl unit of irradiance. Use of WRR is mandatory when working according to the standards of both WMO and ISO. ISO9874 states under paragraph 1.3: the methods of calib ration specified are 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.

The worldwide homogeneity of the meteorological radiation measurements is guaranteed by the World Radiation Center in Davos Switzerland, by maintaining the World Standard Group (WSG) which materialises the World Radiometric Reference.

See www.pmodwrc.ch 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/m

irradiance level. During the outdoor calibration the sun is

typically at 20 to 40° zenith angle, and the total irradiance at a 700 W/m

level.

Table 9.5.1 Calibration hierarchy for pyranometers

WORKING STANDARD CALIBRATION AT PMOD / WRC DAVOS

Calibration of working standard pyranometers: Method: ISO 9846, type 1 outdo or. This working standard has an uncertainty “uncertainty of standard”. The working standard has been calibrated under certain “test conditions of the standard”. The working standard has traceability to WRR world radiometric r e ference.

CORRECTION OF (WORKING) STANDARD CALIBRATION TO STANDARDISED

REFERENCE CONDITIONS

Correction fr om “test conditions of the standard” to “reference conditions” i.e. to normal incidence and 20 °C: Using known (working) standard pyranometer properties: directional, non linearity, offsets, temperature dependence) . This correction has an uncertainty; “uncer tainty of correction”. At Hukseflux we a ls o call the working standard pyranomet e r “standard”.

INDOOR PRODUCT CALIBRATION

Calibration of products, i.e. pyranometers: Method: according to ISO 9847, Type IIc, which is an indoor calibration. This calibration has an uncertainty associated with the method. (In some cases like the BSRN network the product calibration is with a different method; for example again type 1 ou tdoor)

CALIBRATION UNCERTAINTY CALCULATION

ISO 98-3 Guide to the Expression of Uncertainty in Measurement, GUM De ter mination of combined expanded uncert a in ty of calibration of the product, including uncertainty of the working standard, uncertainty of corre c tion, uncertainty of the method (transfer error). The coverage factor must be determined; at Hukseflux we work with a coverage factor k = 2.

SR05-D1A3-PV manual v1801 71/83

9.6 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/m

Table 9.6.1 Meteorological radiation quantities as recommended by WMO (additional symbols by Hukseflux Thermal Sensor). POA stands for Plane of Array irradiance. Th e term originates from ASTM and IEC standards.

SYMBOL DESCRIPTION CALCULATION UNITS ALTERNATIVE

EXPRESSION

E↓

downward irradiance

E↓ = Eg ↓ + El↓

W/m2

H↓

downward radiant exposur e for a specified time interval

H↓ = H

↓ + Hl ↓

J/m

E↑

upward irradiance

E↑ = E

↑

+ E

↑

W/m2

H↑

upward radiant exposure for a specified time interval

H↑ = H

↑ + Hl ↑

J/m

W∙h/m2 Change of

units

E direct solar irradiance

normal to the apparen t

solar zenith angle

W/m2 DNI Direct

Normal

Irradiance

E0 solar constant W/m2

↓

global irradiance;

hemispherical irradiance on a specified, in this case

horizontal surface.*

↓

= E cos θh + E

↓

W/m2

GHI

Global

Horizontal Irradiance

Eg ↓ t

global irradiance; hemispherical irradiance on a specified, in this case

tilted surface.*

Eg ↓ = E∙cos θt + E

↓ t + Er↑ t ***

W/m2 POA Plane of

Array

Ed ↓

downward diffuse solar radiation

W/m

DHI Diffuse

Horizontal

Irradiance

↑

, E

↓

upward / downward long-

wave irradiance

W/m2 E

↑

reflected solar irradiance

W/m2

E* net irradiance

E* = E↓ – E↑

W/m2

T↓

apparent surface temperature**

ºC or K

T↑

apparent sky

temperature**

ºC or K

sunshine duration

θ is the apparent solar zenith angle θ

relative to horizontal, θt relative to a tilted surface g = global, l = long wave, t = tilted *, h = horizontal* * distinction horizontal and tilted from Huk seflux, ** T symbols introduced by Hukseflux, *** contributions of E

↓ t and Er↑ t are Ed ↓ and E

r↑

both corrected for the tilt angle of the

surface

SR05-D1A3-PV manual v1801 72/83

9.7 Appendix on ISO and WMO classification tables

Table 9.7.1 Classification table for pyranometers per ISO 9060 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*.

ISO CLASSIFICATION** TABLE

ISO CLASS

SECONDARY STANDARD

FIRST CLASS

SECOND CLASS

Specification limit Response time (95 %) 15 s 30 s 60 s Zero offset a (respons e to 200 W/m2 net

thermal radiation)

+ 7 W/m2 + 15 W/m2 + 30 W/m2

Zero offset b (response to 5 K/h in a m b ient

temperature)

± 2 W/m2 ± 4 W/m2 ± 8 W/m2

Non-stability (change per year) ± 0.8 % ± 1.5 % ± 3 %

Non-linearity (100 to 1000 W/m2)

± 0.5 %

± 1 %

± 3 %

Directional response

± 10 W/m2

± 20 W/m2

± 30 W/m2

Spectral selectivity (350 to 1 500 x 10-9 m) (WMO 300 to 3 000 x 10

-9

± 3 % ± 5 % ± 10 %

Temperature response (interval of 50 K)** 2 % 4 % 8 %

Tilt response

(0 to 90 ° at 1000 W/m2)

± 0.5 %

± 2 %

± 5 %

ADDITIONAL WMO SPECIFICATIONS

WMO CLASS HIGH QUALITY GOOD QUALITY MODERATE

QUALITY

WMO: achievable accuracy for daily sums*

2 %

5 %

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

CONFORMITY TESTING***

ISO 9060 individual

instrument only : all specs must

comply

group compliance

* 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 for clear-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 %. *** an instrument is subject to conformity testing of its specifications. Depending on the classification, conformity compliance can be proven either by group- or individual compliance. A specification is fulfille d if the mean value of the respective test result does not exceed the corresponding limiting value of the specification for the specific category of instrument.

SR05-D1A3-PV manual v1801 73/83

9.8 Appendix on definition of pyranometer specifications

Table 9.8.1 Definition of pyranometer specifications

SPECIFICATION DEFINITION SOURCE

Response time (95 %)

time for 95 % response. The time in terval between the instant when a stimulus is subjected to a spec ified abrupt change and the instant when the response rea c hes and remains within specified limits around its f inal steady value.The response time is a measure of the thermal inertia inherent in the stabilization period for a final reading.

ISO 90601990 WMO

1.6.3

Zero offset a: (200 W/m

net thermal radiation )

response to 200 W/m

net thermal r a diation (ventilated). Hukseflux assumes that unventilated instr uments have to specify the zero-offset in unventilated – worst case – conditions. Zero offsets are a m easure of the stability of the zer o-point. Zero offset a is vis ib le a t night as a negative offset, the instrument dome irradiates in the far inf r a red to the relatively cold sky. This causes the dome to cool down. The pyranometer sen s or ir radiates to the relatively cool dome, causing a negative of fset. Zero offset

a is also assumed to be present during day time.

ISO 90601990

Zero offset b: (5 K/h in ambient

temperature)

response to 5 K/h change in a m bien t temper ature. Zero offsets are a m easure of the stability of the zer o-point.

ISO 9060-

1990

Non-stability (change per

year)

percentage change in sensitivi ty per year. The dependence of sensitivity resulting from ageing effects which is a measure of the

long-term stability .

ISO 9060-

1990

Non-linearity

(100 to 1000 W/m

)

percentage deviation from the sensitivity at 500 W/m

due to the

change in irradiance with in th e r a nge of 100 W/m

to 1000 W/m2.

Non-linearity has an overlap with directional response, and

therefore should be handled with care in uncertainty evaluation.

ISO

90601990

Directional

response

the range of errors caused by assuming that the normal incidence

sensitivity is valid for all directions when measuring from any direction a beam ra dia tion whose normal incidence irr adiance is 1000 W/m2 . Directional r esponse is a measure of the deviations

from the ideal “cosine behaviour” and its azim uthal variation.

ISO

90601990

Spectral selectivity (350 to 1500 x 10

-9

(WMO 300 to

3000 x 10-9 m)

percentage deviation of th e pr odu c t of s pec tr a l absorptance and spectral transmittance from the corresponding mean within 350 x 10

-9

m to 1500 x 10-9 m and the spectr al distribution of irradiance.

Spectral selectivity is a measure of the spectral s electivity of the

sensitivity.

ISO 90601990

Temperature response

(interval of 50 K)

percentage deviation of the sensitivity due to chan ge in ambient temperature with in an interval of 50 K the temperature of the

pyranometer body.

ISO 9060-

1990

Tilt response

(0° to 90° at 1000 W/m

)

percentage deviation from the sensitivity at 0° tilt (horizontal) due

to change in tilt from 0 ° to 90° at 1000 W/m

irradiance. Tilt

response describes changes of the sensitivity due to changes of

the tilt angle of the receiving s urface.

ISO

90601990

Sensitivity

the change in the response of a mea s uring instrument divided by the corresponding change in the stimulus.

WMO

1.6.3

Spectral range the spectral range of radiation to which the instrument is

sensitive. For a normal pyranometer this should be in the 0.3 to 3 x 10

-6

m range. Some pyranometers w ith c oloured glass domes

have a limited spectral range.

Hukseflux

SR05-D1A3-PV manual v1801 74/83

9.9 Appendix on terminology / glossary

Table 9.9.1 Definitions and references of used terms

TERM DEFINITION (REFERENCE)

Solar energy or solar radiation

solar energy is the electroma gnetic energy emitted by the sun. Solar energy is also 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 spectra l ra nge of 290 to 3 000 x 10

-9

m. Part of the extra-terrestrial solar r a diation penetrates the atmosphere and directly reaches the earth’s surf a ce, while part of it is scattered and / or absorbed by the gas molecules, aeros ol p a rticles, cloud droplets and cloud crystals in the atmosphere. The former is the direct component, th e la tte r is the diffuse

component of the sola r r adiation. (ref: WMO, Huks eflux)

Hemispherical solar radiation

solar radiation received by a plane surface from a 180° field of view angle (solid angle of 2 π sr).(ref: ISO 9060)

Global solar radiation

the solar radiation received fr om a 180° field of view angle on a horizontal surface is referred to as global radiation. Also called GHI. This includes radiation received directly from the s olid angle of the sun’s disc, as well as diffuse sky radiation that has been scattered in traversing the atmosphere. (ref: WMO) Hemispherical so la r radiation received by a horizontal plane surface.

(ref: ISO 9060)

Plane-of-array

irradiance

also POA: hemispherical solar irradiance in the plane of a PV array.

(ref: ASTM E2848-11 / IEC 61724)

Direct solar

radiation

radiation received from a small solid angle centred on the sun’s disc, on a given

plane. (ref: ISO 9060)

Terrestrial or Longwave radiation

radiation not of solar origin but of terrestrial an d a tmospheric origin and having longer wavelengths (3 000 to 100 00 0 x 10

-9

m). In case of down welling El ↓ also the background radia tion from the universe is involved, passing through the ”atmospheric window”. In case of upwelling E

↑, composed of long -wave electromagnetic energy emitted by the earth’s surface and by the gases, aerosols and clouds of the a tm osphere; it is also partly absorbe d within the atmosphere. 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, th e s pec tr um shifts to longer

wavelengths. (ref: WMO)

World Radiometric Reference (WRR)

measurement standa r d r ep r esenting the Sl unit of irradiance with an uncertai nty of less than ± 0.3 % (see the WMO Guide to Meteorological Instruments and Methods 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)

Albedo 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 f or vegetation, up to 0.9 for fresh snow.

Angle of incidence

angle of radiation r elative to the sensor measured from normal incidence (varies from 0° to 90°).

Zenith angle angle of in cidence of radiation, relative to zenith. Equals angle of inciden c e for

horizontally mounted instruments

Azimuth angle

angle of incidence of radiation, projected in the plane of the sens or s urface.

Varies from 0 ° to 360 °. 0 is by definition the cable exit direction, also called

north, east is + 90 °. (ASTM G113-09)

Sunshine duration

sunshine duration during a given period is defined as the sum of that sub-period for which the direct solar irradia nce exceeds 120 W/m

. (ref: WMO)

SR05-D1A3-PV manual v1801 75/83

9.10 Appendix on floating point format conversion

For efficient use of microcontroller capacity some registers in the SR05 contain data in a float or floating point format. In fact, a floating point is an approximation of a real number represented by a number of significant digits (mantissa) and an exponent. For implementation of the floating point numbers, Huks eflux follows the IEEE 754 standard. In this example the floating point of re gister 0x1029 and 0x102A is converted to the decimal value it represents. In the Sensor Manager software and other Modbus tools, floating point data will be converted to decima l data a utomatically.

Example of the calculation of register 0x1029 + 0x102A representing a floating point for the sensitivity of t he sensor, which is 15.14:

Data in register 0x1029, 16754 (MSW) Data in register 0x102A, 15729 (LSW) Double word: (MSW x 2

) + LSW so: (16754 x 216) + 15729 = 1098005873

According to IEEE 754: Sign bit:

1098005873 < 2147483647 so: sign bit = 1; The number 2147483647 is defined by IEEE 754

Exponent: 1098005873 / 2

= 130 (digits after the decimal point are ignored) 130 – 127 = 3 so: exponent = 3; The number 127 is a constant defined by IEEE 754

Mantissa: 130 x 2

= 1090519040 1098005873 – 1090519040 = 7486833 7486833 / 2

= 0.8925

According to IEEE 754, 1 has to be added to get mantissa

0.8925 + 1 = 1.8925 so: mantissa = 1.8925

Calculation of floating point: float = sign bit x mantissa x (2

exponent

) = 1 x 1.8925 x 23 = 15.14

so: floating point = 15.14

SR05-D1A3-PV manual v1801 76/83

9.11 Appendix on function codes, register and coil overview

Table 9.11.1 Supported Modbus function codes

SUPPORTED MODBUS FUNCTION CODES

FUNCTION 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 0x08 Diagnostics 0x0F Write Multiple Coils

0x10

Write Multiple Registers

0x46

Serial communication settings

Table 9.11.2 Modbus registers 0x0000 to 0x0008

MODBUS REGISTERS 0x0000-0x0008

PARAMETER DESCRIPTION OF CONTENT TYPE

OF (R/W)

FORMAT OF DATA

0x0000

Irradiance (W/m2)

Irradiance = value/10

U16

0x0001 Cell temperature (°C) Temperature = (value-250)/10 R U16

0x0002

External temperature

(°C)

Not available, always returns 0

U16

0x0003 Wind speed (m/s) Not available, always returns 0 R U16

0x0004

Factory use only

- - -

0x0005

Cell temperature (°C)

Temperature = (value-1000)/10

U16

0x0006 External temperature

(

Not available, always returns 0 R U16

0x0007

Cell temperature (°C)

Temperature = value/10

S16

0x0008 External temperature

(

Not available, always returns 0 R S16

SR05-D1A3-PV manual v1801 77/83

Table 9.11.3 Modbus registers 0x1000 to 0x1052

MODBUS REGISTERS 0x1000 – 0x1052

PARAMETER DESCRIPTION OF CONTENT TYPE

OF (R/W)

FORMAT OF DATA

0x1000 Modbus address Sensor address in Modbus

network, default = 1

R/W U16

0x1001

Serial communication

settings

Sets the serial

communication, default = 5

R/W

U16

0x1002 + 0x1003

Irradiance

signal in x 0.01 W/m² R S32

0x1004 +

0x1005

Factory use only

0x1006 Sensor body

temperature

In x 0.01 °C R S16

0x1007

Sensor electri c al

resistance

In x 0.1 Ω

U16

0x1008 Scaling factor irradiance Default = 100 R U16 0x1009 Scaling factor

temperature

Default = 100 R U16

0x100A +

0x100B

Sensor voltage output

In x 10-9 V

S32

0x100C to 0x101F

Factory use only

0x1020 to

0x1023

Sensor model

Part one of sensor d es cr iption

String

0x1024 to 0x1027

Sensor model Part two of sensor description R String

SR05-D1A3-PV manual v1801 78/83

MODBUS REGISTERS 0x1000 – 0x1052, continued

PARAMETER DESCRIPTION OF CONTENT TYPE

OF (R/W)

FORMAT OF DATA

0x1028 Sensor serial number R U16

0x1029 +

0x102A

Sensor sensit ivity

In x 10

-6

V/(W/m2)

Float

0x102B Response time In x 0.1 s R U16

0x102C

Sensor resistance

In x 0.1 Ω

U16

0x102D Reserved Always 0 R U16

0x102E +

0x102F

Sensor calibration date

Calibration date of the sensor

in YYYYMMDD

U32

0x1030 to 0x103C

Factory use

0x103D Firmware version R U16 0x103E Hardware version R U16 0x103F +

0x1040

Sensor sensit ivity history 1

In x 10

-6

V/(W/m2)

Default value is 0

R Float

0x1041 + 0x1042

Calibra tio n date h isto ry 1 Former calibration date of the

sensor in YYYYMMDD Default value is 0

R U32

0x1043 + 0x1044

Sensor sensit ivity history 2

See register 0x103F + 0x1040

R Float

0x1045 +

0x1046

Calibra tio n date h isto ry

See register 0x1041 +

0x1042

U32

0x1047 + 0x1048

Sensor sensit ivity history 3

See register 0x103F + 0x1040

R Float

0x1049 +

0x104A

Calibra tio n date h isto ry

See register 0x1041 +

0x1042

U32

0x104B + 0x104C

Sensor sensit ivity history 4

See register 0x103F + 0x1040

R Float

0x104D +

0x104E

Calibra tio n date h isto ry

See register 0x1041 +

0x1042

U32

0x104F + 0x1050

Sensor sensit ivity history 5

See register 0x103F + 0x1040

R Float

0x1051 + 0x1052

Calibra tio n date h isto ry 5 See register 0x1041 +

0x1042

R U32

Note 1: Up to five 16 bit registers can be requested in one request. If requesting six or more registers, use multiple requests.

SR05-D1A3-PV manual v1801 79/83

Please no te th at i f you r data req ue st ne eds a n off set of +1 f or e ach SR05 register number, depending on processing by the network master, this offset applies to coils as we ll. C ons ult the manu al of the dev ice ac t ing as the loc al m aste r.

Table 9.11.4 Coils

COILS

COIL

PARAMETER

DESCRIPTION

TYPE OF

OBJECT TYPE

0 Restart Restart the sensor W Single bit

Reserved

2 Check Measure sensor

electrical resistance

W Single bit

SR05-D1A3-PV manual v1801 80/83

9.12 Appendix on the sensor model name in the register

Table 9.12.1 Modbus registers 0x1020 to 0x1027, sensor model name

MODBUS REGISTERS 0x1020-0x1027

PARAMETER DESCRIPTION OF CONTENT TYPE

FORMAT OF DATA

0x1020 to 0x1023

Sensor model Part one of s en so r d es c r iption R String

0x1024 to

0x1027

Sensor model

Part two of sensor description

String

Registers 32 to 39 will return 8 numbers which can be decoded to find the sensor model name. These 8 numbers (16 bit word or two bytes) are translated to ASCII characters in the following manner. The least significant byte (LSB) of each number corre sponds to the first ASCII character and the most significant byte (MSB) corresponds to the first ASCII character in this register location. The following table illustrates this encoding:

Table 9.12.1 Sensor model name encoding for SR05-D1A3-PV

0x1020 0x1021 0x1022 0x1023 0x1024 0x1025 0x1026 0x1027

content

0x5253

0x3530

0x442D

0x4131

0x2D33

0x5650

0x0000

MSB 0x52 0x35 0x44 0x41 0x2D 0x56 0x00 0x00

LSB

0x53

0x30

0x2D

0x31

0x33

0x50

0x00

ASCII SR 05 -D 1A 3- PV

SR05-D1A3-PV manual v1801 81/83

9.13 EU declaration of conformity

We, Hukseflux Thermal Sensors B.V. Delftechpark 31 2628 XJ Delft The Netherlands

in accordance with the requirements of the following directive:

2011/65/EU The Restriction of Hazardous Substances Directive 2014/30/EU The Electromagn et ic Compatibility Directive

hereby declare under our sole responsibility that:

Product model: SR05-D1A3-PV Product type: Pyranometer

has been designed to comply and is in conformity with the relevant sections and applicable requirements of the following standards:

Emission: IEC/EN 61000-6-1, Class B, RF emission requirements, IEC CISPR11

and EN 55011 Class B requirements

Immunity: IEC/EN 61000-6-2 and IEC 61326 requirements

Report: “EMC test SR05-DA1 v04122015.pdf”, 04 December, 2015

Eric HOEKSEMA Director Delft 07 August, 2018

www.hukseflux.com

Hukseflux Thermal Sensors B.V. reserves the rig ht to change specifications without notice.

Hukseflux SR05, SR05-D1A3-PV User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual