Solar radiation at Earth's surface is typically defined as total radiation across a wavelength rage of 280 to 4000 nm (shortwave radiation). Total solar radiation, direct beam and diffuse, incident on a horizontal surface is defined as global shortwave radiation, or shortwave irradiance (incident radiant flux), and is expressed in Watts per square meter (W m-2, equal to Joules per second per square meter).
Pyranometers are sensors that measure global shortwave radiation. Apogee SP-500 and SP-600 series pyranometers are blackbody thermopile pyranometers, and are sensitive to most of the solar spectrum, thus eliminating spectral errors associated with silicon-cell pyranometers. The SP-510 is designed to measure incoming shortwave radiation and combines a diffuser with the blackbody detector. The SP-610 is designed to measure reflected shortwave radiation from terrestrial surfaces and combines a quartz windows with the blackbody detector. Both models have calibrations traceable to secondary standard blackbody thermopile pyranometers traceable to the world radiation reference in Davos, Switzerland. Specifications for both models meet the International Organization of Standardization (ISO) 9060:2018 Class C (fast response) requirements.
Apogee Instruments SP-510 and SP-610 pyranometers consist of a thermopile detector, acrylic diffuser (SP-510) or glass window (SP-610), heater, and signal processing curcuitry mounted in an anodized aluminum housing, and a cable to connect the sensor to a measurement device. Sensors are potted solid with no internal air space and are designed for continuous measurement of shortwave radiation from the sky (SP-510) and terrestrial surfaces (SP-610) in outdoor environments. SP-510 and SP-610 pyranometers output an analog voltage that is directly proportional to incident shortwave radiation. The analog signal from the sensor is directly proportional to radiation incident on a planar surface (does not have to be horizontal), where the radiation emanates from all angles of a hemisphere.
|ISO 9060:2018||Class C (fast response)||N/A||Class C (fast response)|
|Sensitivity (variable from sensor to sensor, typical values listed)||0.045 mV per W m-2||0.035 mV per W m-2||-|
|Calibration Factor (reciprocal of sensitivity; variable from sensor to sensor, typical values listed)||22 W m-2 per mV||28.5 W m-2 per mV||-|
|Input Voltage Requirement||-||-||5.5 to 24 V|
|Calibration Uncertainty at 1000 W m-2||Less than 3 %||Less than 3 %||Less than 3 %|
|Output Range||0 to 90 mV||0 to 70 mV||Modbus|
|Measurement Range||0 to 2000 W m-2 (net shortwave irradiance)||0 to 2000 W m-2 (net shortwave irradiance)||0 to 2000 W m-2 (net shortwave irradiance)|
|Measurement Repeatability||Less than 1 %||Less than 1 %||Less than 1 %|
|Long-term Drift||Less than 2 % per year||Less than 2 % per year||Less than 2 % per year|
|Non-linearity||Less than 1 %||Less than 1 %||Less than 1 %|
|Detector Response Time||0.5 s||0.5 s||0.5 s (baudrate dependent)|
|Field of View||180°||150°||180°|
|Spectral Range (50 % points)||385 to 2105 nm||370 to 2240 nm||385 to 2105 nm|
|Directional (Cosine) Response||Less than 30 W m-2 at 80° solar zenith||Less than 20 W m-2 for angles between 0 to 60°||Less than 30 W m-2 at 80° solar zenith|
|Temperature Response||Less than 5 % from -15 to 45 C||Less than 5 % from -15 to 45 C||Less than 5 % from -15 to 45 C|
|Zero Offset A||Less than 2 W m-2; Less than 10 W m-2 (heated)||Less than 2 W m-2; Less than 10 W m-2 (heated)||Less than 2 W m-2; Less than 10 W m-2 (heated)|
|Zero Offset B||Less than 5 W m-2||Less than 5 W m-2||Less than 5 W m-2|
|Operating Environment||-50 to 80 C; 0 to 100 % relative humidity||-50 to 80 C; 0 to 100 % relative humidity||-50 to 80 C; 0 to 100 % relative humidity|
|Heater||780 Ω, 15.4 mA current draw and 185 mW power requirement at 12 V DC||780 Ω, 15.4 mA current draw and 185 mW power requirement at 12 V DC||4 mA (heater off); 30 mA (heater on)|
|Uncertainty in Daily Total||Less than 5 %||Less than 5 %||Less than 5 %|
|Dimensions||23.5 mm diameter, 28.7 mm height||23.5 mm diameter, 27.5 mm height||30.5 mm diameter, 37 mm height|
|Mass (with 5 m of cable)||90 g||100 g||140 g|
How to Choose a Pyranometer
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Lecture 3-Shortwave Radiation and Pyranometers
Apogee SP-510 Thermopile Pyranometers Introduction
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Solar radiation at Earth's surface is typically defined as total radiation across a wavelength range of 280 to 4000 nm (shortwave radiation). Total solar radiation, direct beam and diffuse, incident on a horizontal surface is defined as global shortwave radiation, or shortwave irradiance (incident radiant flux), and is expressed in Watts per square meter (W m-2).
Pyranometers are sensors that measure global shortwave radiation. Apogee Instruments offers both silicon-cell and black-body thermopile pyranometers. Silicon-cell pyranometers are only sensitive to a portion of the solar spectrum, approximately 360 to 1100 nm (approximately 80 % of total shortwave radiation is within this range).
Typical applications of silicon-cell pyranometers include:
• Agricultural weather networks
• Ecological weather networks
• Hydrological weather networks
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