Pyrgeometer CGR4

CGR4 Pyrgeometer

The radiation from the sun is mainly shortwave in the range of 300 to 4000 nm (4 μm), including visible and UV radiation. A part of this radiation is absorbed by the clouds, aerosols and molecules in the atmosphere, which thereby heats up and emits long-wave radiation. This is the far-infrared heat energy (FIR) in the range from 4.5 μm to over 40 μm. Both, the short-wave and the long-wave radiation, reach the earth. A part of this is reflected, the remaining radiation heats up the earth's surface. This, in turn, gives rise to long-wave heat energy.

The ratio of incoming and outgoing short and long wave radiation is called energy balance. The short-wave radiation is measured with pyranometers, the long-wave with pyrgeometers.

The Kipp & Zonen CGR4 Pyrgeometer complies with WMO (World Meteorological Organization) guidelines and is traceable to the WISG (World Infrared Standard Group) in Davos, Switzerland, with the CGR4 from Kipp & Zonen being part of this instrument group.

A pyrgeometer generates a signal proportional to the radiation exchange between instrument and sky (or earth) within its field of view. The signal output may be positive or negative.

For example, if the sky is colder than the Pyrgeometer, the Pyrgeometer emits radiation to the sky, and thus the signal output is negative. If the incoming or outgoing far-infrared radiation is to be calculated, the housing temperature near the detector element must be known and recorded simultaneously with the detector signal.

The KGR & Zonen CGR4 Pyrgeometers are equipped with silicon dome which allows infrared radiation to pass through, but are internally coated with a thin coating that blocks short-wave solar radiation and prevents it from reaching the wide-band thermocouple element. The devices are equipped with 10K thermistors (Pt-100 optional) and leveling bays and the white sunshade prevents heating of the housing. The standard length of the cable is 10m and the contacts of the water-proof connector are gold-plated.

The Pyrgeometers do not need any power supply and are delivered calibrated with certificates that are traceable to the WISG (World Infrared Standard Group). The selection of the appropriate model depends on the desired accuracy and performance.

The CGR4 has a special meniscus-shaped silicon dome with a field of view of 180 ° and a hard carbon coating for a uniform spectral sensitivity and as additional surface protection. The sensor element has compensation for changes in sensitivity due to temperature fluctuations.

All pyrgeometer windows consist of materials that absorb a large portion of the short-wave radiation. The window heats up and there is an offset. Therefore, for a higher accuracy, it would be necessary to shield the pyrgeometer from direct solar radiation in order to minimize this effect. The unique design of the CGR4 Pyrgeometer, however, reduces this offset to a negligible level (especially with ventilation) and monitoring the dome temperature or its shading.