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Summary of Contents for Hukseflux SR20
- Page 1 Hukseflux Thermal Sensors USER MANUAL SR20 Secondary standard pyranometer Copyright by Hukseflux | manual v1713 | www.hukseflux.com | info@hukseflux.com...
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Page 2: Warning Statements
Warning statements Putting more than 12 Volt across the sensor wiring can lead to permanent damage to the sensor. Do not use “open circuit detection” when measuring the sensor output. SR20 manual v1713 2/43... -
Page 3: Table Of Contents
Data quality assurance Appendices Appendix on cable extension / replacement Appendix on tools for SR20 Appendix on spare parts for SR20 Appendix on standards for classification and calibration Appendix on calibration hierarchy Appendix on meteorological radiation quantities Appendix on ISO and WMO classification tables... -
Page 4: List Of Symbols
Temperature coefficient Resistance of Pt100 Ω Pt100 Pt100 coefficient Pt100 coefficient Resistance of 10 kΩ thermistor Ω thermistor Steinhart-Hart coefficient α Steinhart-Hart coefficient β Steinhart-Hart coefficient γ (see also appendix 8.6 on meteorological quantities) Subscripts Not applicable SR20 manual v1713 4/43... -
Page 5: Introduction
Introduction SR20 is a solar radiation sensor of the highest category in the ISO 9060 classification system: secondary standard. SR20 pyranometer should be used where the highest measurement accuracy is required. SR20 measures the solar radiation received by a plane surface, in W/m , from a 180 field of view angle. - Page 6 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 SR20 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.
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Page 7: Ordering And Checking At Delivery
Internal temperature sensor. This can be either a Pt100 or a 10 kΩ thermistor. • Specify respectively T1 or T2. Five silica gel bags in an air-tight bag for SR20 desiccant holder. Specify order • number DC01. VU01 ventilation unit. -
Page 8: Quick Instrument Check
4. Inspect the instrument for any damage. 5. Inspect if the humidity indicator is blue. Blue indicates dryness. The colour pink indicates it is humid: in the latter case replace the desiccant (see chapter on maintenance). SR20 manual v1713 8/43... -
Page 9: Instrument Principle And Theory
Instrument principle and theory Figure 2.1 Overview of SR20: cable (standard length 5 metres, optional longer cable) fixation of sun screen (thumb screw) inner dome thermal sensor with black coating outer dome sun screen humidity indicator desiccant holder levelling feet... - Page 10 SR20’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 , is called “hemispherical” solar radiation. The solar radiation spectrum extends roughly from 285 to 3000 x 10 m.
- Page 11 North East South West ISO secondary standard directional response limit zenith angle [°] Figure 2.3 Directional response of a SR20 pyranometer of 4 azimuth angles, compared to secondary standard limits SR20 manual v1713 11/43...
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Page 12: Specifications Of Sr20
Specifications of SR20 3.1 Specifications of SR20 SR20 is a pyranometer of the highest category in the ISO 9060 classification system: secondary standard. It measures the solar radiation received by a plane surface from a field of view angle. This quantity, expressed in W/m , is called “hemispherical”... -
Page 13: Specifications Of Sr20
Table 3.1.1 Specifications of SR20 (continued) SR20 ADDITIONAL SPECIFICATIONS 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 4000 W/m Sensitivity range 7 to 25 x 10... - Page 14 Table 3.1.1 Specifications of SR20 (started on previous pages) Gross weight including 5 m cable 1.2 kg Net weight including 5 m cable 0.85 kg Packaging box of 200 x 135 x 225 mm HEATING Heater operation the heater is not necessarily switched on;...
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Page 15: Dimensions Of Sr20
3.2 Dimensions of SR20 M5 (2x) Figure 3.2.1 Dimensions of SR20 in x 10 SR20 manual v1713 15/43... -
Page 16: Standards And Recommended Practices For Use
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 SR20 manual v1713 16/43... -
Page 17: Specific Use For Outdoor Pv System Performance Testing
8.2.2 Pyranometric Method 4.4 Specific use for outdoor PV system performance testing SR20 is very well applicable in outdoor PV system performance testing. See also model SR20-D2 “digital secondary standard pyranometer with Modbus RTU and 4-20 mA output”... -
Page 18: Installation Of Sr20
Installation of SR20 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. -
Page 19: Installation Of The Sun Screen
5.2 Installation of the sun screen SR20’s sun screen can be installed and removed by using the dedicated thumb screw. See item 2 of the drawing below. The thumb screw can be turned without tools for fixation or loosening of the sun screen, as visualised below. Once the thumb screw has turned the sun screen loose, the screen can be lifted off manually. -
Page 20: Electrical Connection
In order to operate, a pyranometer should be connected to a measurement system, typically a so-called datalogger. SR20 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. -
Page 21: Requirements For Data Acquisition / Amplification
SR20 are available. In case programming for similar instruments is available, this can typically also be used. SR20 can usually be treated in the same way as other thermopile pyranometers. Pyranometers usually have the same programming as heat flux sensors. -
Page 22: Making A Dependable Measurement
* 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). -
Page 23: Reliability Of The Measurement
For first class and secondary standard models (for instance model SR11 first class pyranometer and SR20 secondary standard pyranometer) extra desiccant (in a set of 5 bags in an air tight bag) is available. -
Page 24: 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 repair. The main maintenance actions are: replacement of desiccant •... - Page 25 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...
- Page 26 Table 6.4.1.1 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 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 %.
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Page 27: Maintenance And Trouble Shooting
Maintenance and trouble shooting 7.1 Recommended maintenance and quality assurance SR20 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. -
Page 28: Trouble Shooting
In case of condensation of droplets: disassemble the instrument and dry out the condensation. parts. The inner Arrange to send the sensor back to Hukseflux for diagnosis. dome shows internal condensation SR20 manual v1713 28/43... -
Page 29: Calibration And Checks In The Field
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. -
Page 30: Data Quality Assurance
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 http://www.dqms.com. SR20 manual v1713 30/43... - Page 31 SR20 manual v1713 31/43...
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Page 32: Appendices
Appendices 8.1 Appendix on cable extension / replacement The sensor cable of SR20 is equipped with a M16 straight connector. In case of cable replacement, it is recommended to purchase a new cable with connector at Hukseflux. An alternative is to choose for a Do-it-yourself (DIY) approach; please ask for the DIY connector assembly guide. -
Page 33: Appendix On Tools For Sr20
O-ring SR20 • NOTE: Outer dome, level and sensor of SR20 cannot be supplied as spare parts. In case of possible damage to the SR20, after repair the instrument must be tested to verify performance within specification limits. This is required by ISO 9060. Testing... -
Page 34: Appendix On Standards For Classification And Calibration
Indoor Transfer of Calibration from Reference to Field Pyranometers ISO 9059:1990 Solar energy -- Calibration of ASTM E 816 Standard Test Method for field pyrheliometers by comparison to a Calibration of Pyrheliometers by Comparison to reference pyrheliometer Reference Pyrheliometers SR20 manual v1713 34/43... -
Page 35: Appendix On Calibration Hierarchy
(transfer error). The coverage factor must be determined; at Hukseflux we work with a coverage factor k = 2. SR20 manual v1713... -
Page 36: Appendix On Meteorological Radiation Quantities
In solar energy radiant exposure is often given in W∙h/m Table 8.6.1 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. -
Page 37: Appendix On Iso And Wmo Classification Tables
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. -
Page 38: Appendix On Definition Of Pyranometer Specifications
1.6.3 reading. Zero offset a: response to 200 W/m net thermal radiation (ventilated). (200 W/m 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. -
Page 39: Appendix On Terminology / Glossary
The former is the direct component, the latter is the diffuse component of the solar radiation. (ref: WMO, Hukseflux) Hemispherical solar radiation received by a plane surface from a 180° field of view angle (solid solar radiation angle of 2 π... -
Page 40: Appendix On Converting Resistance To Temperature
8.10 Appendix on converting resistance to temperature SR20 is equipped with an internal temperature sensor. This can be either a Pt100 (SR20- T1 version) or a 10 kΩ thermistor (SR20-T2 version), as ordered. Both versions require the user to measure the resistance of the temperature sensor and convert this value to temperature. -
Page 41: Eu Declaration Of Conformity
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: SR20, 04 January 2014 Eric HOEKSEMA Director Delft 20 April, 2016 SR20 manual v1713 41/43... - Page 43 © 2017, Hukseflux Thermal Sensors B.V. www.hukseflux.com Hukseflux Thermal Sensors B.V. reserves the right to change specifications without notice.
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