Limited Availability ›
This product has limited availability. It will be replaced by: SR30-L. Some accessories, replacement parts, or services may still be available when it is no longer available.
SR20-T2-L ISO Class A Pyranometer with 10K Thermistor
High Measurement Accuracy
Ideal for PV system performance monitoring
weather applications supported water applications supported energy applications supported gas flux and turbulence applications supported infrastructure applications supported soil applications supported


The SR20-T2, manufactured by Hukseflux Thermal Sensors, is an ISO 9060:2018 spectrally flat Class A (secondary standard) pyranometer that measures solar short-wave radiation in a full hemisphere of the sky. It has a built-in case temperature sensor and embedded heater for removing dew and light rain. It connects directly to a Campbell Scientific data logger and is designed for applications that require high measurement accuracy in demanding applications such as scientific meteorological observation networks and utility scale solar-energy-power production sites.

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Benefits and Features

  • Low temperature dependence
  • Embedded 1.5 W heater to reduce effects of dew deposition
  • Embedded 10K temperature sensor
  • Ultra robust connector, desiccant holder, and sun screen
  • Temperature dependence characterized and supplied for each instrument
  • Directional response tested on each instrument


Technical Description

The SR20-T2 pyranometer measures the hemispherical solar radiation received by a plane surface, in W/m2, from a 180° field of view. The SR20 can be deployed indoors with lamp-based solar simulators or more commonly outdoors under the sun. Its orientation depends on the application and may be installed horizontally, tilted for plane or array irradiance, positioned on a sun tracker with shadow-ring for diffuse measurements, or inverted for reflected radiation.

The SR20-T2’s low temperature dependence makes it an ideal candidate for use under very cold and very hot conditions. The temperature dependence of each 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 SR20 is equipped with an internal temperature sensor. Campbell Scientific supplies the T2 version, which has a 10 kohm thermistor. The T1 version, in contrast, has a PT100 and is available upon request. 

The embedded heater reduces measurement errors caused by early-morning dew deposition. Campbell Scientific recommends using the instrument in accordance with the recommended practices of ISO, WMO and ASTM.

The output of the SR20-T2 is analog. The SR20-D2-L model, in contrast, offers two other types of commonly used irradiance outputs: digital via Modbus RTU over 2-wire RS-485, and analogue 4 to 20 mA output (current loop).


Sensor High-quality blackened thermopile protected by two glass domes
Measurement Description Measures hemispherical solar radiation
ISO Classification Spectrally flat Class A (secondary standard) pyranometer (ISO 9060:2018 )
WMO Performance Level High-quality pyranometer
Response Time 3 s (95%)
Zero Offset A 5 W/m2 (unventilated), 2.5 W/m2 (ventilated) (response to 200 W/m2 net thermal radiation)
Zero Offset B ≤ -2 W/m2 (response to 5 K/h change in ambient temperature)
Non-Stability ≤ -0.5% change per year
Non-Linearity ≤ -0.2% (100 to 1000 W/m2)
Directional Response < ±10 W/m2
Spectral Selectivity < ±3% (0.35 to 1.5 x 10-6 m)
Temperature Response < ±1% (-10° to +40°C), < 0.4% (-30° to +50°C) with correction in data processing
Tilt Response < ±0.2% (0 to 90° at 1000 W/m2)
Heater 1.5 W (at 12 Vdc)
Steady-state Zero Offset 0 to -8 W/m2 (caused by heating)
Calibration Uncertainty < 1.2% (k=2)
Level Accuracy < 0.1° (bubble entirely in ring)
Sensor Resistance Range 100 to 200 ohm
Operating Temperature Range -40° to +80°C
Field of View (FOV) 180°
Measurement Range 0 to 4000 W/m2
Sensitivity 7 to 25 x 10-6 V/(W/m2)
Spectral Range 285 to 3000 x 10-9 m (20% transmission points)


Please note: The following shows notable compatibility information. It is not a comprehensive list of all compatible products.


Product Compatible Note
CR1000 (retired)
CR800 (retired)
CR850 (retired)

Mounting Equipment

Product Compatible Note

Additional Compatibility Information

Power Considerations

The SR20-T2 heater is a 1.5 W heater at 12 Vdc. The SW12 power out port on the CR800/850, CR1000, and other data loggers can supply the needed 0.125 A for the heater, as that port can supply 0.9 A at 20°C. More typically, relays controlled by the data logger digital I/O ports are used to control the power supply.

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