Introduction
Solar radiation is typically measured using a pyranometer for global solar radiation, but precise measurement of direct solar radiation requires a pyrheliometer. This is achieved with an automatic two-axis sun tracker that aligns the pyrheliometer with the sun, allowing for accurate measurement of direct solar radiation and diffuse solar radiation using a shading assembly.

System Configurations
Sun trackers provide stable mounting for pyrheliometers, moving horizontally and vertically to follow the solar arc. They use stepping motors controlled by a microprocessor, requiring accurate site data for precise sun positioning.

Applications
Sun trackers are essential in solar monitoring networks for weather forecasting, climate models, atmospheric research, pollution forecasting, and materials testing. They are crucial for renewable energy applications, including photovoltaic systems and solar collectors, aiding in research, quality control, and efficiency monitoring.

Baseline Surface Radiation Network (BSRN)
BSRN is a global network of solar monitoring stations providing accurate radiation data, crucial for understanding climate systems and global changes. Kipp & Zonen equipment is widely used in BSRN and other international climate projects.

Choice of Sun Tracker
The 2AP sun tracker is robust, suitable for extreme conditions, and used globally in high-quality solar monitoring stations. The SOLYS 2 tracker offers BSRN-level performance, is easy to install, and operates efficiently with solar power. It features an integrated GPS, multi-colour LEDs for status indication, and an Ethernet port for updates and diagnostics.

Features and Specifications
Both 2AP and SOLYS 2 trackers offer high accuracy and low maintenance. The SOLYS 2 is fully automatic with integrated GPS, while the 2AP requires manual setup with Win2AP software. Both models support active sun tracking with optional sun sensors and have various mounting options for additional instruments.

Technical Specifications
Operating temperature ranges from -50 °C to +50 °C with optional heaters. The trackers support both AC and DC power inputs, with SOLYS 2 offering a lower power consumption. They provide high torque for sun tracking and have various mounting plates for radiometers and other instruments.