The SR20-T2, manufactured by Hukseflux Thermal Sensors, is an ISO 9060 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 datalogger 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.Read More
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 analog 4 to 20 mA output (current loop).
|Measurements Made||Hemispherical solar radiation|
|ISO 9060 Classification||Secondary standard pyranometer|
|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 Range||7 to 25 x 10-6 V/(W/m2)|
|Spectral Range||285 to 3000 x 10-9 m (20% transmission points)|
The SR20-T2 is compatible with the following mounts: 27065, CM225, CM255, and CM255LS.
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 dataloggers 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 datalogger digital I/O ports are used to control the power supply.