Introduction
Solar radiation is crucial for biological and geophysical processes. The sun's average intensity at the earth's atmosphere is 1367 W/m². As solar rays pass through the atmosphere, they are absorbed and scattered, resulting in direct and diffuse components reaching the earth's surface.

Pyrheliometer Overview
Pyrheliometers measure direct beam solar irradiance with a 5° field of view, known as Direct Normal Incidence (DNI). They use a collimation tube with precision apertures and a quartz window to filter solar radiation between 200 nm and 4000 nm. These instruments include rain shields and alignment aids.

CHP 1 Pyrheliometer
The CHP 1 is a passive pyrheliometer that offers reliability and durability without power requirements. It uses a detector similar to high-level pyranometers, minimizing temperature fluctuation effects and providing fast response times. It includes Pt-100 and 10 kΩ thermistor temperature sensors and meets ISO and WMO criteria for First Class Normal Incidence Pyrheliometers.

SHP1 Pyrheliometer
The SHP1 combines CHP 1 design with smart interface advantages, offering digital signal processing and optimized interfaces for industrial systems. It features improved response time, integrated temperature sensors, and digital polynomial functions for temperature sensitivity correction. The SHP1 operates on low power and a wide voltage range, making it suitable for power-critical applications.

Applications
The SHP1 is ideal for renewable energy applications, particularly in solar energy data acquisition and control systems. It provides accurate solar irradiance data for photovoltaic research and solar farm site prospecting.

Interfacing and Outputs
The SHP1 offers analogue outputs (0 to 1 V or 4 to 20 mA) and a 2-wire RS-485 interface with Modbus® protocol. It supports easy connection to data loggers and industrial networks. Users can access measurement data, instrument settings, calibration history, and status information.

Specifications
Both CHP 1 and SHP1 exceed ISO and WMO performance criteria. They have a spectral range of 200 to 4000 nm, a full viewing angle of 5°, and can operate in temperatures from -40 °C to +80 °C. The SHP1 has a response time of less than 2 seconds and low power consumption.

Conclusion
Kipp & Zonen pyrheliometers are designed for high-performance solar radiation monitoring, suitable for meteorological stations and concentrated solar energy applications. They offer reliable, accurate measurements with easy installation and maintenance.