Hukseflux

Thermal Sensors

SR20Analogue Class A pyranometer
SR20 is a solar radiation sensor of the highest category in the ISO 9060 classification system: spectrally
flat Class A. SR20 pyranometer should be used where the highest measurement accuracy is required. It
is often used with dataloggers that can directly accept its analog voltage output.

Figure 1 SR20 spectrally flat Class A pyranometer.

Introduction
SR20 measures the solar radiation received by aplane surface, in W/m2, from a 180 o field of view
angle. SR20 enables you to attain the highest
measurement accuracy at the best value formoney and excels in demanding applications.
After a thorough programme of acceptancetesting, SR20 spectrally flat Class A was releasedin February 2013; it is now a household name.

Improved measurement accuracy
In order to improve overall measurement
accuracy, Hukseflux effectively targeted twomajor sources of measurement uncertainty:
calibration and “zero offset a”.
The initial calibration uncertainty is reduced toless than 1.2 %. The “zero offset a” specificationof SR20 is < 5 W/m2 unventilated. Ventilated(with VU01) it is just 2.5 W/m2.
Figure 2 Dual setup in PV system performance monitoring.
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Thermal Sensors

Lowest total cost of ownership

SR20 design

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

SR20 pyranometer uses a state of the art
thermopile sensor with black coated surface, twodomes and an anodised aluminium body. Theconnector, desiccant holder and sun screen
fixation are ultra robust and designed forindustrial use. All parts are specified for use
across SR20’s entire rated operating temperature
range.

Pyranometers must be calibrated every 2 years.
Such recalibration is considered good practice forany measuring instrument and is required byISO, IEC and WMO standards covering PV system
performance – and meteorological monitoring.
Cost of recalibration however can be high.
Hukseflux’ worldwide calibration network will help
you reduce these costs. Learn more about
Hukseflux pyranometer calibration services.

345

2
61

EU
USA
BRA

JPN
CHN
IND
SEA
AUS

Figure 3 To reduce total cost of ownership: make use of
the worldwide Hukseflux calibration organisation.

Demanding applications
SR20’s low temperature response makes it anideal candidate for use under very cold and very
hot conditions.
The temperature response of every individual
instrument is tested and supplied as a second
degree polynomial. This information can be used
for further reduction of temperature dependence
during post-processing.
The incorporated heater can be used to reduce
measurement errors caused by early-morning
dew and frost deposition.

Compliant with IEC 61724-1:2021,
Class A
SR20 complies, without the need for additional
accessories, with IEC requirements. It includes
heating for dew and frost mitigation.

7111098Figure 4 Overview of SR20:(1) cable, (2) fixation of sun screen, (3) inner dome, (4)thermal sensor with black coating, (5) outer dome, (6)sun screen, (7) humidity indicator, (8) desiccant holder,(9) levelling feet, (10) bubble level,(11) connector.

Figure 5 SR20 with its sun screen removed.

Standards
Applicable instrument classification standards areISO 9060 and WMO-No. 8. Included in delivery as
required by ISO 9060:2018 test certificates fortemperature response and directional response.
Calibration is according to ISO 9847. PV related
standards are IEC 61724 and ASTM E2848.

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Thermal Sensors

Choosing the right instrument
Pyranometers are subject to classification inthree classes according to ISO 9060.
From Class C to Class B and from Class B to ClassA, the achievable accuracy improves by a factor
2.
Measurement accuracy does not only depend on
instrument properties, but also on measurement
conditions. A very accurate instrument willquickly underperform without a regular scheduleof maintenance.
Our pyranometer selection guide assists you inchoosing the right instrument.
Whatever your application is: Hukseflux offers
the highest accuracy in every class at the most
attractive price level.

Suggested use••

PV system performance monitoring
scientific meteorological observations

SR20 specifications
Measurandhemispherical solar
radiation

ISO classification
ISO 9060:2018

spectrally flat Class Apyranometer
WMO performance levelhigh quality pyranometerIEC 61724-1 compliancemeets Class A
PV monitoring system
requirements
Calibration uncertainty< 1.2 % (k = 2)
Zero offset a< 5 W/m2 unventilated
Zero offset a
2.5 W/m2 ventilated
Calibration traceability
to WRR
Spectral range
285 to 3000 x 10-9 m
Sensitivity (nominal)
15 x 10-6 V/(W/m2)
Rated operating temperature -40 to +80 oC
range
Temperature response< ± 1 % (-10 to +40 °C)< ± 0.4 % (-30 to +50 °C)
with correction indataprocessing
Temperature response test report includedof individual instrument
Directional response test
report included to 95 ˚of individual instrument
Temperature sensor
Pt100
or 10 kΩ thermistor
Heater
1.5 W at 12 VDCStandard cable length5mOptions••Figure 6 SR20 side view.

See also••••••SR30 digital spectrally flat Class A
pyranometer with heating and tilt sensor
SR20-D2 digital spectrally flat Class A
pyranometer with Modbus RTU and 4-20 mA
outputalternative instruments: SR15 and SR05
series for lower accuracy measurements
PMF01 and PMF02 pyranometer mounting
fixtures, also for POA (Plane of Array)the making of SR20 documented
view our complete product range of solar
sensors

longer cable, in multiples of 5 metres
ventilated with VU01 ventilation unit

About Hukseflux
Hukseflux is the leading expert in measurementof energy transfer. We design and manufacture
sensors and measuring systems that support theenergy transition. We are market leaders in solar
radiation- and heat flux measurement.
Customers are served through the main office in
the Netherlands, and locally owned
representations in the USA, Brazil, India, China,Southeast Asia and Japan.

Interested in this product?
E-mail us at: info@hukseflux.com

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Hukseflux

Thermal Sensors

SR20 analogue Class A pyranometer
This overview summarises the main features and benefits of SR20. Customers prefer Hukseflux pyranometers for their unsurpassed measurement
accuracy and their lowest total cost of ownership.

Best measurement accuracy• spectrally flat
• low zero offsets• low calibration uncertainty• best temperature dependence• heated: compliant with IEC 61724-1 Class A

Best connector• interchangeable cables• IP67 grade• for industrial use

Best sun screen• sealed• corrosion protection of body• no dry-cooking of bubble level

Lowest total cost of ownership• efficient worldwide calibration support• ISO/IEC 17025 calibration available• fast servicing organisation

Best desiccant cartridge• visible indicator of instrument health• rugged aluminium design• serviceable by user

Best humidity protection• wrench-operated• o-ring compressed to spec
• desiccant service interval > 2 years© Copyright by Hukseflux . Version 2313. Page 4/4. For Hukseflux Thermal Sensors go to www.hukseflux.com or e-mail us: info@hukseflux.com