USER MANUAL SR03 - Hukseflux - Thermal Sensors
Contents
1. 3 If applicable remove the optional sun screen using the hex key see chapter on installation of the sun screen Inspect the bubble level 4 Inspect the instrument for any damage sr03 manual v1302 8 45 Thermal Sensors Hukseflux 2 Instrument principle and theory Figure 2 1 Overview of SRO3 cable standard length 5 metres optional longer cable cable gland thermal sensor with black coating glass dome 5 sensor body levelling feet mounting hole bubble level sr03 manual v1302 9 45 Hukseflux Thermal Sensors SRO3 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 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 pyranom2. 8 2 2 Pyranometric Method 4 4 Specific use in meteorology and climatology The World Meteorological Organization WMO is a specialised agency of the United Nations It is the UN system s authoritative voice on the state and behaviour of the earth s atmosphere and climate WMO publishes WMO No 8 Guide to Meteorological Instruments and Methods of Observation in which a table is included on level of performance of pyranometers Nowadays WMO conforms itself to the ISO classification system sr03 manual v1302 17 45 Hukseflux Thermal Sensors 5 Installation of SRO3 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 desirable The horizon should be as free from obstacles as possible Ideally there should be no objects between the course of the sun and the instrument Mechanical mounting thermal insulation preferably use connection by bolts to the bottom plate of the instrument A pyranometer is sensitive to thermal shocks Do not mount the instrument with the body in direct thermal contact to the mounting plate so always use the levelling feet also if the mounting is not horizontal do not mount the instrument on objects that become very hot black coated metal plates Instrument mounting with 2 bolts 2 x M5 bolt at 65 x 10 m centre to centre distance on north south axis con
3. for example model SRO3 this may slowly develop into a defect For first class and secondary standard models for instance model SR20 secondary standard pyranometer extra desiccant in a set of 5 bags in an air tight bag is available sr03 manual v1302 22 45 Hukseflux Thermal Sensors Another way to improve measurement reliability is to introduce redundant sensors e The use of redundant instruments allows remote checks of one instrument using the other as a reference which leads to a higher measurement reliability e 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 6 3 Speed of repair and maintenance instrument lifetime 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 repair The main maintenance actions are e replacement of desiccant not applicable for SR03 e replacement of cabling For optimisation of dependability a user should e estimate the expected lifetime of the instrument e design a sche
4. involves use outside the specified range of application or if it involves accidental damage or misuse The warranty expires when anyone other than Hukseflux makes modifications to or repairs the products Hukseflux is in no event liable for damages to its customers or anyone claiming through these customers associated to the goods or services it supplies sr03 manual v1302 43 45 Hukseflux Thermal Sensors 9 11 EC declaration of conformity We Hukseflux Thermal Sensors B V Elektronicaweg 25 2628 XG Delft The Netherlands in accordance with the requirements of the following directive 2004 108 EC The Electromagnetic Compatibility Directive hereby declare under our sole responsibility that Product model SR03 Type Pyranometer has been designed to comply and is in conformity with the relevant sections and applicable requirements of the following standards Emission EN 61326 1 2006 Immunity EN 61326 1 2006 Emission EN 61000 3 2 2006 Emission EN 61000 3 3 1995 Al 2001 A2 2005 jo o O lt I N Kees VAN DEN BOS Director Delft December 12 2011 sr03 manual v1302 44 45 2013 Hukseflux Thermal Sensors B V www hukseflux com Hukseflux Thermal Sensors B V reserves the right to change specifications without notice
5. standard instrument in the field according to ISO 9847 6 lifetime judge if the instrument should be reliable for another 2 years assessment or if it should be replaced 7 6 years parts if applicable necessary replace the parts that are most replacement exposed to weathering cable cable gland sun screen NOTE use Hukseflux approved parts only 8 internal if applicable open instrument and inspect replace O rings inspection dry internal cavity around the circuit board 9 recalibration recalibration by side by side comparison to a higher standard instrument indoors according to ISO 9847 or outdoors according to SO9846 sr03 manual v1302 26 45 Hukseflux Thermal Sensors 7 2 Trouble shooting Table 7 2 1 Trouble shooting for SRO3 The sensor Check the electrical resistance of the sensor between the green does not give and white wire Use a multimeter at the 200 Q range Measure the sensor any signal resistance first with one polarity than reverse the polarity Take the average value The typical resistance of the wiring is 0 1 Q m Typical resistance should be the typical sensor resistance of 100 to 200 Q plus 1 5 Q for the total resistance of two wires back and forth of each 5 m Infinite resistance indicates a broken circuit zero or a low resistance indicates a short circuit Check if the sensor reacts to light put the multimeter at its most sensitive range of DC voltage measurement typi
6. 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 conditions also involve the question whether or not the measurement at the location of measurement is representative of the quantity that should be measured sr03 manual v1302 21 45 Hukseflux Thermal Sensors 6 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 e related to the reliability of the pyranometer and its design manufacturing calibration hardware reliability e related to the reliability of the measurement uncertainty measurement reliability which involves hardware reliability as well as condition of use Most of the hardware reliability is the responsibility of the instrument manufacturer The reliability of the measurement however is a joint responsibility of instrument manufacturer and user As a function of user requirements taking into account measurement conditions and environmental conditions the user will select an instrument of a certain class and define maintenance support procedures In many situations there is a limit to a realistically attainable accuracy level This is due to conditions that are beyond control once the measurement system is in place Typica
7. with a critical review of the measured data preferably checking against other measurements is the preferred way to obtain a reliable measurement Table 7 1 1 Recommended maintenance of SRO3 If possible the data analysis and cleaning 1 and 2 should be done on a daily basis 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 down 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 2 weeks cleaning use a soft cloth to clean the dome of the instrument persistent stains can be treated with soapy water or alcohol 3 6 months inspection inspect cable guality inspect cable glands inspect 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 desiccant desiccant replacement not applicable for SR03 replacement 5 2 years recalibration recalibration by side by side comparison to a higher
8. 0 1990 standard Solar energy specification and classification of instruments for measuring hemispherical solar and direct solar radiation distinguishes between 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 sr03 manual v1302 10 45 Hukseflux Thermal Sensors 1 2 23 a cc 1 me Solar radiation Ys S 9 0 8 s 5 sm pyranometer oe 0 6 response v n Ow ui U g n 0 4 82 28 0 2 0 100 1000 10000 wavelength x 10 9 m 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 sr03 manual v1302 11 45 Hukseflux Thermal Sensors 3 Specifications of SRO3 3 1 Specifications of SRO3 SRO3 measures the solar radiation received by a plane surface from a from a 180 field of view angle This quantity expressed in W m is called hemispherical solar radiation Working completely passive using a thermopile sensor SRO3 generates a small output voltage proportional to this flux It can only be used in combination with a suitable measurement system 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 Specifications o
9. 2 41 45 Hukseflux Thermal Sensors 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 electromagnetic 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 spectral range of 290 to 3 000 x 10 m Part of the extra terrestrial solar radiation penetrates the atmosphere and directly reaches the earth s surface while part of it is scattered and or absorbed by the gas molecules aerosol particles cloud droplets and cloud crystals in the atmosphere The former is the direct component the latter is the diffuse component of the solar radiation ref WMO Hukseflux Hemispherical solar radiation solar radiation received by a plane surface from a 180 field of view angle solid angle of 2 n sr ref ISO 9060 Global solar radiation the solar radiation received from 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 solid angle of the sun s disc as well as diffuse sky radiation that has been scattered in traversing the atmosphere ref WMO Hemispherical solar radiation received by a horizontal pla
10. 2 SR03 fast response second class solar radiation sensor 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 SRO3 may be used 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 Model SR03 TR houses a 4 20 mA transmitter for easy read out by dataloggers commonly used in the industry For more information see the chapter on SR03 TR sr03 manual v1302 6 45 Hukseflux Thermal Sensors 1 Ordering and checking at delivery 1 1 Ordering SRO3 The standard configuration of SRO3 is with 5 metres cable Common options are e Longer cable in multiples of 5 m Specify total cable length e SRO3 TR first class pyranometer with 4 20 mA transmitter Standard setting is 4 mA at 0 W m and 20 mA at 1600 W m Specify setting and total cable length e Sun screen Specify order number SCRO1 Supply of products is subject to Hukseflux General Conditions of Sale The product warranty involving repair or replacement without charge for product or working hours is 24 months Hukseflux does not accept any liability for losses or damages related to use of the supplied products See the appendix and Hukseflux General Conditions of Sale for detailed statements on war
11. 45 Hukseflux Thermal Sensors 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 Table 6 4 1 1 Preliminary estimates of achievable uncertainties of measurements with pyranometers The estimates are based on typical pyranometer properties and calibration uncertainty for sunny clear sky days and 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 Yo Estimates are based on 1 s sampling IMPORTANT NOTE there is no international consensus on uncertainty evaluation of pyranometer measurements so this table should not be used as a fo
12. 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 sr03 manual v1302 28 45 Hukseflux Thermal Sensors 7 4 Data quality assurance Quality assurance can be done by e analysing trends in solar irradiance signal e plotting the measured irradiance against mathematically generated expected values e comparing irradiance measurements between sites e 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 http www dqms com sr03 manual v1302 29 45 Hukseflux Thermal Sensors 8 SRO3 TR 8 1 Introduction SRO3 TR As a special version of SRO3 Hukseflux offers model SRO3 TR a fast response second class pyranometer with 4 20 mA transmitter SRO3 TR is a second class solar radiation sensor that is applied in most common solar radiation observations SRO3 TR pyranometer is used for general meteorological observations building physics and solar collector testing However because of its fast response time it is ideally suited for PV applications where it will match the response time of the panels more closely than other pyranometer models SRO3 TR houses a 4 20 mA transmitter for easy read out by dataloggers commonly used in the industry Using SRO3 TR is easy The pyranom
13. Hukseflux Thermal Sensors USER MANUAL SRO3 Fast response second class pyranometer Copyright by Hukseflux manual v1302 www hukseflux com info hukseflux com Thermal Sensors Hukseflux Warning statements Putting more than 12 Volt across the sensor wiring VA N can lead to permanent damage to the sensor Do not use open circuit detection when measuring AN the sensor output sr03 manual v1302 2 45 Hukseflux Thermal Sensors Contents Warning statements Contents List of symbols Introduction 1 PB W Nr N H W Ne AUNE O O O 0 O 0 O 60 O EO WOWMWANAN NONA O MUWUUU URA PE DWWW NE bb O0 34300U pF WNHr N H FP UN Hr 5 WNb H O Ordering and checking at delivery Ordering SR03 Included items Ouick instrument check Instrument principle and theory Specifications of SRO3 Specifications of SRO3 Dimensions of SRO3 Standards and recommended practices for use Classification standard General use for solar radiation measurement General use for sunshine duration measurement Specific use in meteorology and climatology Installation of SRO3 Site selection and installation Installation of the optional sun screen Electrical connection Requirements for data acquisition amplification Making a dependable measurement The concept of dependability Reliability of the measurement Speed of repair and maintenance instrument lifetime Uncertainty evaluation Maintenance and trouble shooting Recommen
14. UCT 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 outdoor CALI BRATION UNCERTAINTY CALCULATION ISO 98 3 Guide to the Expression of Uncertainty in Measurement GUM Determination of combined expanded uncertainty of calibration of the product including uncertainty of the working standard uncertainty of correction uncertainty of the method transfer error The coverage factor must be determined at Hukseflux we work with a coverage factor k 2 sr03 manual v1302 38 45 Hukseflux Thermal Sensors 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 The term originates from ASTM and IEC standards SYMBOL DESCRIPTION CALCULATION UNITS ALTERNATIVE EXPRESSION EI downward irradiance EJ E E W m HI downward radiant exposure HJ H Hi m for a specified time interval Et upward irradiance EJ E E W m Ht upward radiant e
15. a acquisition by short circuiting the data acquisition input with a 100 Q resistor Look at the output Check if the output is close to 0 W m The sensor Check the presence of strong sources of electromagnetic radiation radar radio signal shows etc unexpected Check the condition of the shielding variations Check the condition of the sensor cable Check if the cable is not moving during the measurement The dome Arrange to send the sensor back to Hukseflux for diagnosis shows internal condensation sr03 manual v1302 27 45 Hukseflux Thermal Sensors 7 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 Standard Solar 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 In case of field comparison ISO recommends field calibration to a higher class pyranometer Hukseflux suggests also allowing use of sensors of the same model and class because intercomparisons of similar instruments has the advantage that they suffer from the same offsets It is therefore just as good to compare to pyranometers of the same br
16. acitive noise In an electrically quiet environment the SRO3 cable can however be extended without problem to 100 meters If done properly the sensor signal although small will not significantly degrade because the sensor resistance is very low so good immunity to external sources and because there is no current flowing so no resistive losses Cable and connection specifications are summarised below NOTE the body of SRO3 contains connector blocks that can be used for the internal connection of a new cable See the chapter on electrical connections Usually it is easier to connect a new extended cable inside the pyranometer body cable than to make a good weatherproof connection to an existing cable Table 9 1 1 Preferred specifications for cable extension of SRO3 General please consult Hukseflux for instructions or use Hukseflux supplied parts Cable 2 wire shielded with copper conductor at Hukseflux 3 wire shielded cable is used of which only 2 wires are used Sealing sealed at the sensor side against humidity ingress Core resistance lt 0 1 Q m Outer diameter 4 to 6 x 103 m to fit cable gland Length cables should be kept as short as possible in any case the total cable length should be less than 100 m Outer sheet with specifications for outdoor use for good stability in outdoor applications Connection either solder the new cable core and shield to the original sensor cable and mak
17. adiation 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 http 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 outdoor 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 reference CORRECTION OF WORKING STANDARD CALIBRATION TO STANDARDISED REFERENCE CONDITIONS Correction from 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 uncertainty of correction At Hukseflux we also call the working standard pyranometer standard INDOOR PROD
18. and 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 cloudless conditions 10 days under 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 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 independently calibrated 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 instruments 6 for second class radiometers to correct deviations of more than 10 Lower deviations should be interpreted as acceptable and should not lead to a revised sensitivity 7 for 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
19. anometer and 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 Standard Test Method for Calibration of a Pyranometer Using a Pyrheliometer ISO 9847 1992 Solar energy Calibration of field pyranometers 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 Standard Test Method for Indoor Transfer of Calibration from Reference to Field Pyranometers ISO 9059 1990 Solar energy Calibration of field pyrheliometers by comparison to a reference pyrheliometer ASTM E 816 Standard Test Method for Calibration of Pyrheliometers by Comparison to Reference Pyrheliometers sr03 manual v1302 37 45 Hukseflux Thermal Sensors 9 5 Appendix on calibration hierarchy The World Radiometric Reference WRR is the measurement standard representing the SI unit of irradiance It was introduced in order to ensure world wide homogeneity of solar radiation measurements and is in use since 1980 The WRR was determined from the weighted mean of the measurements of a group of 15 absolute cavity radiometers which were fully characterised It has an estimated accuracy of 0 3 The WMO introduced its mandatory use in its status in 1979 The world wide homogeneity of the meteorological r
20. cally the 100 x 10 VDC range or lower Expose the sensor to strong light source for instance a 100 W light bulb at 1 x 107m distance The signal should read gt 2 x 10 V now Darken the sensor either by putting something over it or switching off the light The instrument voltage output should go down and within one minute approach O V Check the data acquisition by applying a 1 x 10 V source to it in the 1 x 10 V range The sensor Note that night time signals may be negative down to 5 W m on clear windless signal is nights due to zero offset a unrealistically Check if the pyranometer has clean domes high or low Check the location of the pyranometer are there any obstructions that could explain the measurement result Check the orientation levelling of the pyranometer Check if the right calibration factor is entered into the algorithm Please note that each sensor has its own individual calibration factor as documented in its calibration certificate Check if the voltage reading is divided by the calibration factor in review of the algorithm Check the condition of the wiring at the logger Check the cable condition looking for cable breaks Check the range of the data logger signal can be negative this could be out of range or the amplitude could be out of range Check the data acquisition by applying a 1 x 10 V source to it in the 1 x 10 V range Look at the output Check if the output is as expected Check the dat
21. ded maintenance and quality assurance Trouble shooting Calibration and checks in the field Data quality assurance SRO3 TR Introduction SRO3 TR Dimensions of SRO3 TR Appendices Appendix on cable extension replacement Appendix on tools for SR03 Appendix on spare parts for SRO3 Appendix on standards for classification and calibration Appendix on calibration hierarchy Appendix on meteorological radiation guantities Appendix on ISO and WMO classification tables Appendix on definition of pyranometer specifications Appendix on terminology glossary Appendix on conditions of sale warranty and liability EC declaration of conformity sr03 manual v1302 OONN NU PA W N 3 45 Hukseflux Thermal Sensors List of symbols Quantities Symbol Voltage output Sensitivity Temperature Electrical resistance Solar irradiance Solar radiant exposure Time in hours somaanec see also appendix 9 6 on meteorological quantities Subscripts Not applicable sr03 manual v1302 Unit V V W m C Q W m W h m h 4 45 Hukseflux Thermal Sensors Introduction SRO3 is the fastest ISO 9060 second class compliant pyranometer available Due to major advances in thermopile sensing technology SRO3 achieves a 95 response time in just 1 second SRO3 is optimally suited for PV system performance monitoring where long term stability and synchronous response time between the PV module array and pyranometer are requi
22. dule of regular maintenance e 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 Hukseflux pyranometers are designed to be suitable for the intended use for at least 5 years under normal meteorological conditions Factory warranty granting free of charge repair for defects that are clearly traceable to errors in production is 2 years The product expected lifetime is defined as the minimum number of years of employment with normal level of maintenance support until the instrument is no longer suitable for its intended use cannot be repaired For pyranometers the product expected lifetime depends heavily on the environmental conditions Examples of environments with reduced expected lifetime are areas with high levels of air pollution and areas with high levels of salt in the air Both cause enhanced corrosion It is not possible to give a generally applicable statement about expected lifetime In Hukseflux experience it is not realistic to expect a lifetime longer than 10 years except in very dry environments such as very dry tropical or polar climates sr03 manual v1302 23 45 Hukseflux Thermal Sensors Examples Hukseflux model LPO2 second class pyranometer has been produced since 2004 In 2012 the number of instruments in th
23. e a waterproof connection using cable shrink or use gold plated waterproof connectors Always connect shield sr03 manual v1302 35 45 Hukseflux Thermal Sensors 9 2 Appendix on tools for SRO3 Table 9 2 1 Specifications of tools for SRO3 tooling required for sun screen fixation and removal hex key 2 x 103 m tooling reguired for cable gland fixation and removal spanner size 15 x 10 m tooling reguired for wire fixation and removal screwdriver blade width 2 x 103 m internal wiring inside SR03 body 9 3 Appendix on spare parts for SRO3 e Levelling feet set of 3 e SRO3 cable specify length in multiples of 5 m sealed at one end e Cable gland SR03 e O ring SRO3 sr03 manual v1302 36 45 Hukseflux Thermal Sensors 9 4 Appendix on standards for classification and calibration Both ISO and ASTM have standards on instrument classification and methods of calibration The World Meteorological Organisation WMO has largely adopted the ISO classification system Table 9 4 1 Pyranometer standardisation in ISO and ASTM STANDARDS ON INSTRUMENT CLASSIFICATION AND CALI BRATION ISO STANDARD EQUIVALENT ASTM STANDARD ISO 9060 1990 Solar energy Specification and classification of instruments for measuring hemispherical solar 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 pyr
24. e field is estimated to be above 4000 Hukseflux quality management s interpretation of service records is that the Mean Time Between Failure MTBF of LPO2 is larger than 6 years only defects and large repairs are counted as failures SRO3 fast response second class pyranometer is based on similar technology 6 4 Uncertainty evaluation The uncertainty of a measurement 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 Guide to Expression of Uncertainty in Measurement or GUM 6 4 1 Evaluation of measurement uncertainty under outdoor conditions Hukseflux actively participates in the discussions about pyranometer measurement uncertainty we also provide spreadsheets reflecting the latest state of the art to assist our users in making their own evaluation The input to the assessment is summarised 1 The formal evaluation of uncertainty should be performed in accordance with ISO 98 3 Guide to the Expression of Uncertainty in Measurement GUM 2 The specifications of the instrument according to the list of ISO 9060 classification of pyranometers and pyrheliomete
25. easuring from any 9060 direction a beam radiation whose normal incidence irradiance is 1990 1000 W m Directional response is a measure of the deviations from the ideal cosine behaviour and its azimuthal variation Spectral percentage deviation of the product of spectral absorptance and ISO selectivity 350 spectral transmittance from the corresponding mean within 350 x 9060 to 1500 x 10 m 10 m to 1500 x 10 m and the spectral distribution of irradiance 1990 WMO 300 to Spectral selectivity is a measure of the spectral selectivity of the 3000 x 10 m sensitivity Temperature percentage deviation of the sensitivity due to change in ambient ISO response temperature within an interval of 50 K the temperature of the 9060 interval of 50 K pyranometer body 1990 Tilt response percentage deviation from the sensitivity at 0 tilt horizontal due ISO 0 to 90 at to change in tilt from 0 to 90 at 1000 W m irradiance Tilt 9060 1000 W m response describes changes of the sensitivity due to changes of 1990 the tilt angle of the receiving surface Sensitivity the change in the response of a measuring instrument divided by WMO the corresponding change in the stimulus 1 6 3 Spectral range the spectral range of radiation to which the instrument is Hukseflux sensitive For a normal pyranometer this should be in the 0 3 to 3 x 10 m range Some pyranometers with coloured glass domes have a limited spectral range sr03 manual v130
26. es the datalogger accepts a voltage input Usually a 100 amp precision resistor is used to convert the current to a voltage this will then be in the 0 4 to 2 VDC range This resistor must be put in the wire of the sensor In the two latter cases the user must check that the low side of the input channel is connected to ground and the high side to a positive voltage in the reguired range sr03 manual v1302 31 45 Thermal Sensors Hukseflux 8 2 Dimensions of SRO3 TR O 9 Figure 8 2 1 Overview of SR03 TR 1 cable standard length 5 metres optional longer cable 2 cable gland 3 thermal sensor with black coating 4 glass dome 5 sensor body 6 transmitter housing 7 levelling feet bubble level sr03 manual v1302 32 45 Hukseflux Thermal Sensors 160 278 Figure 8 2 2 Dimensions of SRO3 TR in 10 m sr03 manual v1302 33 45 Hukseflux Thermal Sensors sr03 manual v1302 34 45 Hukseflux Thermal Sensors 9 Appendices 9 1 Appendix on cable extension replacement The sensor cable can be removed and installed by the user provided that the cable is sealed at the sensor side against humidity ingress Please consult Hukseflux for instructions on cable preparation or use Hukseflux supplied parts SRO3 is equipped with one cable Keep the distance between data logger or amplifier and sensor as short as possible Cables act as a source of distortion by picking up cap
27. eter can be connected directly to commonly used data logging systems The irradiance in W m is calculated by using the transmitter s output In LPO2 TR s standard configuration the 4 to 20 mA output corresponds to a transmitted range of 0 to 1600 W m This range can be adjusted at the factory upon request Figure 8 1 1 SRO3 TR fast response second class pyranometer with 4 20 mA transmitter sr03 manual v1302 30 45 Hukseflux Thermal Sensors Table 8 1 1 Specifications of SRO3 TR SRO3 TR SPECIFICATIONS Description fast response second class pyranometer with 4 20 mA transmitter Transmitted range 0 to 1600 W m Output signal 4 to 20 x 10 A Principle 2 wire current loop Supply voltage 7 2 to 35 VDC Options adapted transmitted range longer cable in multiples of 5 m For definition of pyranometer ISO 9060 specifications see the appendix Table 8 1 2 Reguirements for data acguisition and amplification eguipment with the SRO3 TR configuration Capability to measure 4 20 mA or measure currents or measure voltages The SRO3 TR has a 4 20 mA output There are several possibilities to handle this signal It is important to realise that the signal wires not only act to transmit the signal but also act as power supply Some dataloggers have a 4 20 mA input In that case the connection can be directly made Some dataloggers have the capability to measure currents In some cas
28. eter 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 e athermal sensor with black coating It has a flat spectrum covering the 200 to 50000 x 10 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 e a glass dome This dome limits the spectral range from 285 to 3000 x 10 m cutting off the part above 3000 x 10 m while preserving the 180 field of view angle Another function of the dome is that it shields the thermopile sensor from the environment convection rain e asecond inner glass dome For a first class pyranometer two domes are used and not one single dome This construction provides an additional radiation shield resulting in a better thermal equilibrium between the sensor and inner dome compared to using a single dome The effect of having a second dome is a strong reduction of instrument offsets Pyranometers can be manufactured to different specifications and with different levels of verification and characterisation during production The ISO 906
29. f SR03 continued on next pages SRO3 SPECIFICATI ONS REQUIRED BY ISO 9060 ISO classification ISO 9060 1990 second class pyranometer WMO performance level WMO No 8 moderate quality pyranometer seventh edition 2008 Response time 95 1 s Zero offset a response to 200 W m lt 15 W m unventilated net thermal radiation Zero offset b response to 5 K h lt 4 W m change in ambient temperature Non stability lt 1 change per year Non Linearity lt 1 100 to 1000 W m Directional response lt 25 W m Spectral selectivity lt 5 0 35 to 1 5 x 10 m Temperature response lt 3 10 to 40 C Tilt response lt 2 0 to 90 at 1000 W m For the exact definition of pyranometer ISO 9060 specifications see the appendix sr03 manual v1302 12 45 Hukseflux Thermal Sensors Table 3 1 1 Specifications of SRO3 continued SRO3 ADDITIONAL SPECI FI CATI ONS Measurand hemispherical solar radiation Measurand in SI radiometry units irradiance in W m Optional measurand sunshine duration Field of view angle 180 Measurement range 0 to 2000 W m Sensitivity range 7 to 25 x 10 V W m Sensitivity nominal 15 x 10 V W m Expected voltage output application under natural solar radiation 0 1 to 50 X 10 W Measurement function reguired programming E U S Measurement fu
30. g 5 m cable 0 3 kg Packaging box of 170 x 90 x 230 x 10 m sr03 manual v1302 13 45 Hukseflux Thermal Sensors Table 3 1 1 Specifications of SRO3 started on previous pages CALI BRATION Calibration traceability to WRR Calibration hierarchy from WRR through ISO 9846 and ISO 9847 applying a correction to reference conditions Calibration method indoor calibration according to ISO 9847 Type Ilc Calibration uncertainty lt 1 8 k 2 Recommended recalibration interval 2 years Reference conditions 20 C normal incidence solar radiation horizontal mounting irradiance level 1000 W m Validity of calibration based on experience the instrument sensitivity will not change during storage During use under exposure to solar radiation the instrument non stability specification is applicable MEASUREMENT ACCURACY Uncertainty of the measurement statements about the overall measurement uncertainty can only be made on an individual basis See the chapter on uncertainty evaluation Achievable uncertainty 95 confidence level daily totals 10 reference WMO No 8 seventh edition 2008 Achievable uncertainty 95 confidence level hourly totals 20 reference WMO No 8 seventh edition 2008 VERSIONS OPTIONS 4 20 mA transmitter creating a 4 20 mA output signal option code TR with adapted housing standa
31. hat 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 expected accuracies are for clear days at mid latitudes and that the uncertainty estimate does not include uncertainty due to calibration ISO CLASSIFICATI ON TABLE ISO CLASS SECONDARY FIRST CLASS SECOND STANDARD CLASS Specification limit Response time 95 15s 30 s 60 s Zero offset a response to 200 W m net 7 W m 15 W m 30 W m thermal radiation Zero offset b response to 5 K h in ambient 2 W m 4 W m 8 W m temperature Non stability change per year 0 8 1 5 3 Non linearity 100 to 1000 W m 0 5 1 3 Directional response 10 W m 20 W m 30 W m Spectral selectivity 350 to 1 500 x 10 m 3 5 10 WMO 300 to 3 000 x 10 m Temperature response interval of 50 K 2 4 8 Tilt response 0 5 2 5 0 to 90 at 1000 W m ADDITIONAL WMO SPECIFICATIONS WMO CLASS HIGH QUALITY GOOD QUALITY MODERATE QUALITY WMO expected accuracy for daily sums 2 5 10 Yo WMO expected accuracy for hourly sums 3 8 Yo 20 Yo WMO expected accuracy for minute sums WMO resolution 1 W m 5 W m 10 W m smallest detectable change CONFORMITY TESTI NG ISO 9060 individual group compliance group instrument
32. ization period for a final 1 6 3 reading Zero offset a response to 200 W m net thermal radiation ventilated ISO 200 W m net Hukseflux assumes that unventilated instruments have to specify 9060 thermal the zero offset in unventilated worst case conditions 1990 radiation Zero offsets are a measure of the stability of the zero point Zero offset a is visible at night as a negative offset the instrument dome irradiates in the far infra red to the relatively cold sky This causes the dome to cool down The pyranometer sensor irradiates to the relatively cool dome causing a negative offset Zero offset a is also assumed to be present during daytime Zero offset b response to 5 K h change in ambient temperature ISO 5 K h in ambient Zero offsets are a measure of the stability of the zero point 9060 temperature 1990 Non stability percentage change in sensitivity per year The dependence of ISO change per sensitivity resulting from ageing effects which is a measure of the 9060 year long term stability 1990 Non linearity percentage deviation from the sensitivity at 500 W m due to the ISO 100 to 1000 change in irradiance within the range of 100 W m to 1000 W m 9060 W m Non linearity has an overlap with directional response and 1990 therefore should be handled with care in uncertainty evaluation Directional the range of errors caused by assuming that the normal incidence ISO response sensitivity is valid for all directions when m
33. l limiting conditions are e the measurement conditions for instance when working at extreme temperatures when the instrument temperature is at the extreme limits of the rated temperature range e the environmental conditions for instance when installed at a sub optimal measurement location with obstacles in the path of the sun e the 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 e 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 solved by regular inspection and cleaning e 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 e 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 non serviceable sensors like Hukseflux second class pyranometers
34. n Turn the set screw using the hex key and lift of the sun screen 1 hex key 2 sun screen 3 set screw 5 3 Electrical connection In order to operate a pyranometer should be connected to a measurement system typically a so called datalogger SRO3 is a passive sensor that does not need any power Cables generally act as a source of distortion by picking up capacitive noise We recommend keeping the distance between a datalogger or amplifier and the sensor as short as possible For cable extension see the appendix on this subject Table 5 3 1 The electrical connection of SRO3 WI RE COLOUR MEASUREMENT SYSTEM Sensor output White Voltage input Sensor output Voltage input or ground Shield Bare metal Analogue ground Housing Thermopile A Figure 5 3 1 Electrical diagram of SR03 The shield is connected to the sensor body sr03 manual v1302 19 45 Hukseflux Thermal Sensors Table 5 3 2 Standard internal connection of SRO3 at the internal printed circuit board SENSOR PRINTED CIRCUIT COLOUR CODE WIRE Plus White Shield SH Bare metal TR Not connected unless the sensor has a trimmed sensitivity or limited sensitivity range 5 4 Requirements for data acquisition amplification The selection and programming of dataloggers is the responsibility of the user Please contact the supplier of the data acquisition and amplification equipment to see if directions fo
35. nction optional programming for sunshine duration programming according to WMO guide paragraph 8 2 2 Reguired readout 1 differential voltage channel or 1 single ended voltage channel input resistance gt 10 Q Optional readout 1 temperature channel in case optional temperature sensor is ordered Rated operating temperature range 40 to 80 C Sensor resistance range 100 to 200 Q Required sensor power zero passive sensor Spectral range 20 transmission points 285 to 3000 x 10 m Standard governing use of the instrument 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 Standard cable length see options 5m Cable diameter 4 x 103 m Cable gland cable diameter range accepts cable diameters from 4 to 6 x 10 m Cable replacement cable can be removed and installed by the user provided that the cable is sealed at the sensor side against humidity ingress Consult Hukseflux for instructions or use Hukseflux supplied parts Mounting 2 x M5 bolt at 65 mm centre to centre distance on north south axis Levelling bubble level and adjustable levelling feet are included Levelling accuracy lt 0 4 bubble entirely in ring IP protection class IP 67 Gross weight including 5 m cable 0 5 kg Net weight includin
36. nd incoming solar radiation Dimensionless number that varies between 0 and 1 Typical albedo values are lt 0 1 for water from 0 1 for wet soils to 0 5 for dry sand from 0 1 to 0 4 for vegetation up to 0 9 for fresh snow Angle of angle of radiation relative to the sensor measured from normal incidence varies incidence from 0 to 90 Zenith angle angle of incidence of radiation relative to zenith Equals angle of incidence for horizontally mounted instruments Azimuth angle angle of incidence of radiation projected in the plane of the sensor surface Varies from 0 to 360 0 is by definition the cable exit direction also called north west is 90 Sunshine duration 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 ref WMO sr03 manual v1302 42 45 Hukseflux Thermal Sensors 9 10 Appendix on conditions of sale warranty and liability Delivery of goods is subject to Hukseflux General Conditions of Sale Hukseflux has the following warranty and liability policy Hukseflux guarantees the supplied goods to be new free from defects related to bad performance of materials and free from faults that are clearly related to production and manufacturing Warranty on products is valid until 24 months after transfer of ownership The warranty does not apply if the application involves significant wear and tear if it
37. ne surface ref ISO 9060 Plane of array also POA hemispherical solar irradiance in the plane of a PV array irradiance ref ASTM E2848 11 IEC 61724 Direct solar radiation received from a small solid angle centred on the sun s disc on a given radiation plane ref ISO 9060 Terrestrial or radiation not of solar origin but of terrestrial and atmospheric origin and having Longwave longer wavelengths 3 000 to 100 000 x 10 m In case of downwelling E also radiation the background radiation from the universe is involved passing through the atmospheric window In case of upwelling E t composed of long wave electromagnetic energy emitted by the earth s surface and by the gases aerosols and clouds of the atmosphere it is also partly absorbed within the atmosphere For a temperature of 300 K 99 99 of the power of the terrestrial radiation has a wavelength longer than 3 000 x 10 m and about 99 per cent longer than 5 000 x 10 m For lower temperatures the spectrum shifts to longer wavelengths ref WMO World measurement standard representing the SI unit of irradiance with an uncertainty Radiometric of less than 0 3 see the WMO Guide to Meteorological Instruments and Reference Methods of Observation 1983 subclause 9 1 3 The reference was adopted by WRR the World Meteorological Organization WMO and has been in effect since 1 July 1980 ref ISO 9060 Albedo ratio of reflected a
38. nection through the pyranometer flange Instrument mounting with one bolt not applicable Performing a representative 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 mounted parallel to the plane of interest In case a pyranometer is not mounted horizontally or in case the horizon is obstructed the representativeness of the location becomes an important element of the measurement See the chapter on uncertainty evaluation Levelling in case of horizontal mounting only use the bubble level and levelling feet The optional sun screen must be removed for inspection of the bubble level Instrument orientation by convention with 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 inverted installation WMO recommends a distance of 1 5 m between soil surface and sensor reducing the effect of shadows and in order to obtain good spatial averaging sr03 manual v1302 18 45 Hukseflux Thermal Sensors 5 2 Installation of the optional sun screen The optional SCRO1 sun screen can be installed and removed using a hex key size 2 x 10 m See the drawing below DD 3 Figure 5 2 1 Installation and removal of sun scree
39. only compliance all specs must comply 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 we use the expression 1 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 fulfilled 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 sr03 manual v1302 40 45 Hukseflux Thermal Sensors 9 8 Appendix on definition of pyranometer specifications Table 9 8 1 Definition of pyranometer specifications SPECIFICATION DEFINITION SOURCE Response time time for 95 response The time interval between the instant ISO 95 when a stimulus is subjected to a specified abrupt change and the 9060 instant when the response reaches and remains within specified 1990 limits around its final steady value The response time is a measure WMO of the thermal inertia inherent in the stabil
40. pyranometer is called dependable if it is reliable i e measuring within required uncertainty limits for most of the time and if problems once they occur can be solved quickly The requirements for a measurement with a pyranometer may be expressed by the user as e required uncertainty of the measurement see following paragraphs e requirements for maintenance and repairs possibilities for maintenance and repair including effort to be made and processing time e arequirement 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 of e the instrument class e the calibration procedure uncertainty e the duration of instrument employment under natural sunlight involving the instrument stability specification e the measurement conditions such as tilting ventilation shading instrument temperature e maintenance mainly fouling e the environmental conditions Therefore ISO 9060 says statements about the overall measurement uncertainty under outdoor conditions can only be made on an individual basis taking all these factors into account defined at Hukseflux as all factors outside the instrument that are relevant to
41. r use with the SRO3 are available In case programming for similar instruments is available this can typically also be used SRO3 can usually be treated in the same way as other thermopile pyranometers Pyranometers usually have the same programming as heat flux sensors In case of the SRO3 TR version the output is 4 to 20 x 10 A See the chapter on the SRO3 TR Table 5 4 1 Requirements for data acquisition and amplification equipment for SRO3 in the standard configuration Capability to measure small voltage preferably 5 x 10 V uncertainty signals Minimum requirement 20 x 10 V uncertainty valid for the entire expected temperature range of the acquisition amplification equipment Capability for the data logger or the to store data and to perform division by the sensitivity to software calculate the solar irradiance E U S Formula 0 1 Data acquisition input resistance gt 1x10 Q Open circuit detection open circuit detection should not be used unless this is done WARNING separately from the normal measurement by more than 5 times the sensor response time and with a small current only Thermopile sensors are sensitive to the current that is used during open circuit detection The current will generate heat which is measured and will appear as an offset sr03 manual v1302 20 45 Hukseflux Thermal Sensors 6 Making a dependable measurement 6 1 The concept of dependability A measurement with a
42. ranty and liability 1 2 Included items Arriving at the customer the delivery should include e pyranometer SR03 e cable of the length as ordered e product certificate matching the instrument serial number e any other options as ordered Please store the certificate in a safe place sr03 manual v1302 7 45 Hukseflux Thermal Sensors 1 3 Quick instrument check A quick test of the instrument can be done by using a simple hand held multimeter and a lamp 1 Check the electrical resistance of the sensor between the green and white wire Use a multimeter at the 200 Q range Measure the sensor resistance first with one polarity than reverse the polarity Take the average value The typical resistance of the wiring is 0 1 m Typical resistance should be the typical sensor resistance of 100 to 200 Q plus 1 5 Q for the total resistance of two wires back and forth of each 5 m Infinite resistance indicates a broken circuit zero or a low resistance indicates a short circuit 2 Check if the sensor reacts to light put the multimeter at its most sensitive range of DC voltage measurement typically the 100 x 10 VDC range or lower Expose the sensor to a strong light source for instance a 100 W light bulb at 0 1 m distance The signal should read gt 2 x 10 V now Darken the sensor either by putting something over it or switching off the light The instrument voltage output should go down and within one minute approach O V
43. rd setting is 4 x 10 A at O W m and 20 x 10 A at 1600 W m for specifications see the chapter on SR03 TR Longer cable in multiples of 5 m option code total cable length ACCESSORIES Sun screen for use on SR03 SCRO1 Separate amplifiers AC100 and AC420 Hand held read out unit LI19 sr03 manual v1302 14 45 Thermal Sensors Hukseflux 3 2 Dimensions of SRO3 59 22 Figure 3 2 1 Dimensions of SR03 in 10 m sr03 manual v1302 15 45 Hukseflux Thermal Sensors 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 WMO ASTM STANDARD ISO 9060 1990 Not available WMO No 8 Guide to Solar energy specification and Meteorological Instruments classification of instruments for and Methods of Observation measuring hemispherical solar and chapter 7 measurement of direct solar radiation radiation 7 3 measurement of global and diffuse solar radiation 4 2 General use for solar radiation measurement Table 4 2 1 S
44. red SRO3 is a solar radiation sensor that can be applied in general observations It measures the solar radiation received by a plane surface from a field of view angle of 1800 This quantity expressed in W m2 is called hemispherical solar radiation Contrary to photodiode based instruments SRO3 has a spectrally flat response across the full solar spectrum SRO3 pyranometer is used for general meteorological observations building physics and solar collector testing However because of its fast response time it is ideally suited for PV applications where it will match the response time of the panels more closely than other pyranometer models Use on ships and airplanes in conjunction with tilt sensors is also a possibility In combination with the right software also sunshine duration may be measured Using SRO3 is easy It can be connected directly to commonly used datalogging systems The irradiance in W m2 is calculated by dividing the SRO3 output a small voltage by the sensitivity This sensitivity is provided with SRO3 on its calibration certificate The central equation governing SRO3 is E U S Formula 0 1 The instrument should be used in accordance with the recommended practices of ISO WMO and ASTM Suggested use for SRO3 e PV system performance monitoring e on buoys and on aircrafts Figure 0 1 SRO3 fast response second class pyranometer sr03 manual v1302 5 45 Hukseflux Thermal Sensors Figure 0
45. rmal reference Pyranometer season latitude uncertainty uncertainty uncertainty class minute totals hourly totals daily totals ISO 9060 at solar noon at solar noon secondary summer mid latitude 2 1 2 0 1 9 standard eguator 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 eguator 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 Yo 5 9 6 2 SR03 eguator 7 8 5 5 5 3 pole 29 5 21 6 18 0 winter mid latitude 11 4 8 1 9 9 6 4 2 Calibration uncertainty From 2011 to 2012 calibration of SR03 has been improved New procedures were developed in close cooperation with PMOD World Radiation Center in Davos Switzerland Our 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 calibration hierarchy sr03 manual v1302 25 45 Hukseflux Thermal Sensors 7 Maintenance and trouble shooting 7 1 Recommended maintenance and quality assurance SRO3 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
46. rs are entered as limiting values of possible errors to be analysed as type B evaluation of standard uncertainty per paragraph 4 3 7 of GUM A priori distributions are chosen as rectangular 3 A separate estimate has to be entered to allow for estimated uncertainty due to the instrument maintenance level 4 The calibration uncertainty has to be entered Please note that Hukseflux calibration uncertainties are lower than those of alternative equipment These uncertainties 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 incidence 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 observation may be sufficient 7 In case of special measurement conditions typical specification values are chosen These should for instance account for the measurement conditions shaded unshaded ventilated unventilated horizontal tilted and environmental conditions clear sky cloudy working temperature range sr03 manual v1302 24
47. tandards with recommendations for instrument use in solar radiation measurement STANDARDS FOR INSTRUMENT USE FOR HEMISPHERICAL SOLAR RADIATION ISO STANDARD EQUIVALENT WMO ASTM STANDARD ISO TR 9901 1990 ASTM G183 05 WMO No 8 Guide to Solar energy Field Standard Practice for Field Meteorological Instruments pyranometers Recommended Use of Pyranometers and Methods of Observation practice for use Pyrheliometers and UV chapter 7 measurement of Radiometers radiation 7 3 measurement of global and diffuse 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 sr03 manual v1302 16 45 Hukseflux Thermal Sensors 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 sunshine duration
48. xposure Hl Hg H J Jim W h m Change of for a specified time interval units E direct solar irradiance W m DNI Direct normal to the apparent Normal solar zenith angle Irradiance Eo solar constant W m Egl h global irradiance Ey E cos On W m GHI Global hemispherical irradiance on Egl Horizontal a specified in this case Irradiance horizontal surface Es Lt global irradiance Eg E cos 6 W m POA Plane of hemispherical irradiance on Eg 4 Erte Array a specified in this case tilted surface Es downward diffuse solar W m DHI Diffuse radiation Horizontal Irradiance E t Ei upward downward long W m wave irradiance Et reflected solar irradiance W m Ex net irradiance E EL Ef W m TJ apparent surface 2C or K temperature Tt apparent sky 2C or K temperature SD sunshine duration h 8 is the apparent solar zenith angle Oh relative to horizontal 6 relative to a tilted surface g global long wave t tilted h horizontal distinction horizontal and tilted from Hukseflux T symbols introduced by Hukseflux contributions of Eg and E f are Eg andE t both corrected for the tilt angle of the surface sr03 manual v1302 39 45 Hukseflux Thermal Sensors 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 t
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