SR20 pyranometer

Secondary standard pyranometer

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SR20 is a pyranometer of the highest category in the ISO 9060 classification system: secondary standard. This solar radiation sensor is used where the highest measurement accuracy is required. It measures the solar radiation received by a plane surface, in W/m2, from a 180o field of view angle. SR20 secondary standard pyranometer enables you to attain the highest measurement accuracy and excels in demanding applications. After a thorough programme of acceptance testing, SR20 was released February 2013.


In order to improve overall measurement accuracy, Hukseflux effectively targeted two major sources of measurement uncertainty: calibration and “zero offset a”.
The initial calibration uncertainty is reduced to less than 1.2 %, an improvement of 15 % relative to competing models. The “zero offset a” specification of SR20 is 5 W/m2 unventilated. Competing models state 12 W/m2 unventilated and 7 W/m2 ventilated.


The temperature dependence 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. SR20’s low temperature dependence makes it an ideal candidate for use under very cold and very hot conditions. The incorporated heater reduces measurement errors caused by early-morning dew deposition.


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

Click on images in Gallery for detailed views of SR20 pyranometer


Pyranometers are subject to classification in three classes according to ISO 9060. From second class to first class and from first class to secondary standard, 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 will quickly underperform without a regular schedule of maintenance. Our selection guide assists you in choosing the right instrument.
Whatever your application is: Hukseflux offers the highest accuracy in every class at the most attractive price level.


  • PV system performance monitoring
  • scientific meteorological observations
  • reference instrument for comparison
  • extreme climates (tropical / polar)


  • longer cable, in multiples of 5 metres


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