Introduction
Pyrgeometers are instruments used for the precise measurement of far infrared radiation, specifically measuring incoming thermal radiation from the sky and clouds, and outgoing thermal radiation from the ground. They are widely used in meteorology, hydrology, and climate research due to their reliable all-weather performance and portability.

Specifications and Features
The CGR 3 and CGR 4 pyrgeometers are key models, with the CGR 3 being ideal for horticulture and agriculture due to its compact size and sealed construction. The CGR 4 is noted for its scientific accuracy and is used in top-level solar radiation monitoring networks. Both models feature silicon windows with internal coatings to block short-wave solar radiation, integrated bubble levels, and waterproof connectors.

Applications
Pyrgeometers are used globally in various environments, from the Antarctic to deserts, for accurate radiation energy balance measurements. They are designed for long operating life with minimal maintenance.

System Integration
Kipp & Zonen offers a range of compatible products and accessories to extend the capabilities of their pyrgeometers, including ventilation units, sun trackers, data loggers, and amplification devices. The CVF 3 ventilation unit helps maintain dome cleanliness and temperature stability, while the AMPBOX converts low output signals to a standard industrial signal.

Performance and Calibration
The CGR 4 pyrgeometer features a silicon meniscus dome with a hard-carbon coating for enhanced spectral response and surface protection. It compensates for temperature sensitivity changes, reducing the need for dome temperature measurements or shading. Calibration certificates traceable to the World Infrared Standard Group ensure measurement accuracy.

Technical Specifications
The CGR 4 offers a 180° field of view, operates within a temperature range of -40°C to +80°C, and covers a spectral range of 4.5 to 42 μm. It has a response time of less than 18 seconds and a sensitivity of 5 to 15 µV/W/m². The CGR 3 has similar specifications but with a 150° field of view.

Conclusion
Kipp & Zonen pyrgeometers are essential tools for precise measurement of far infrared radiation, offering robust performance and integration capabilities for various scientific and environmental applications.