Pyrgeometers
Pyrgeometers are devices that measure longwave radiation. As the name suggests, this is a radiation with long wavelengths, more specifically called far-infra-red radiation. It is typically between 3 μm to 1,000 μm within the infrared range of electromagnetic radiation. For reference, visible light has a wavelength between 380 and 750 nm.
Longwave radiation is the atmospheric radiation not emitted by the sun but reflected from the Earth’s surface, atmosphere and clouds. Measuring it is different from only measuring sunlight. It can be divided into two parts. The radiation reflected from the atmosphere and clouds is called downward longwave radiation and the one that is reflected upwards by the Earth’s surface is called upward longwave radiation.
Since pyrgeometers are used to measure longwave radiation other than solar radiation, multiple components are added to its design so that the results are accurate. The actual sensor is located underneath a silicone dome with a solar blind filter. The dome ensures that a part of the solar radiation is blocked while the blind filter coating at the top of the dome cuts off more wavelengths so that what remains is only longwave radiation.
Additionally, a thermal sensor inside the silicone dome possesses a black coating to absorb longwave radiation and transfers it to heat in the form of conductive heat flux by the sensor. Then, the thermopile located in the body of the sensor converts the heat flux to a voltage that can be easily measured.
As pyrgeometers are used to measure longwave radiation, they are extremely useful in climatological and general networks in meteorology to monitor the weather, and more long-term the climate. Another application can be found in agriculture where these devices are used in networks to detect frost.
Product Line
IR02-TR
Manufacturer: Hukseflux
IR02-TR is a pyrgeometer suitable for longwave irradiance measurement in meteorological applications. The instrument can be heated, which improves measurement accuracy as it prevents dew deposition on its window. IR02-TR houses a 4-20 mA transmitter for easy read-out by dataloggers commonly used in the industry.
Specifications:
- Measurand: longwave radiation
- Optional measurand: sky temperature
- Optional measurand: surface temperature
- Output: 4 to 20 mA
- Principle: 2-wire current loop
- Spectral range IR02-TR: 4.5 to 40 x 10-6 m
- Field of view angle: 150°
- Response time (95 %): 18 s
- Rated operating temperature range: -40° to +80° C
- Temperature dependence: < ±3 % (-10 to +40 °C)
IR02 (Pyrgeometer with heater)
Manufacturer: Hukseflux
IR02 is a pyrgeometer suitable for longwave irradiance measurements in meteorological applications. The instrument can be heated, which improves measurement accuracy as it mitigates dew and frost on its window. Because of features like this, IR02 is popular and often used in agricultural networks.
Specifications:
- Optional measurand: sky temperature, surface temperature
- Sensitivity (nominal): 15 x 10⁻⁶ V/(W/m²)
- Spectral range: 4.5 to 42 x 10⁻⁶ m
- Field of view angle: 150 °
- Response time: 18 s
- Rated operating temperature range: -40 to +80 °C
- Temperature dependence: < ± 3 % (-10 to +40 °C)
IR20 & IR20WS (Research grade pyrgeometers)
Manufacturer: Hukseflux
IR20 is a research grade pyrgeometer suitable for high-accuracy longwave irradiance measurement in meteorological applications. IR20 is capable of measuring during both day and night. In absence of solar radiation, model IR20WS offers even better accuracy because of its wider spectral range.
Specifications:
- Measurand: longwave radiation
- Optional measurand: sky temperature, surface temperature
- Sensitivity (nominal): 17 x 10⁻⁶ V/(W/m²)
- Spectral range IR20: 4.5 to 40 x 10⁻⁶ m (nominal)
- Spectral range IR20WS: 1.0 to 50 x 10⁻⁶ m
- Field of view angle: 180°
- Response time (95 %): 3 s
- Rated operating temperature range: -40 to +80 °C
- Temperature dependence: < ± 0.4 % (-30 to +50 °C)