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 requiring power. 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. Each unit comes with a calibration certificate traceable to the World Radiometric Reference.

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, making it suitable for power-critical applications, and exceeds ISO and WMO performance criteria.

Applications
The SHP1 is ideal for renewable energy applications, particularly in solar energy data acquisition and control systems. It provides accurate solar irradiance data essential 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, serial numbers, calibration history, and more.

Specifications
Both CHP 1 and SHP1 meet First Class standards with response times under 5 seconds and minimal non-stability and non-linearity. They operate in temperatures from -40 °C to +80 °C and handle maximum irradiance of 4000 W/m². The SHP1's power consumption is minimal, with options for different analogue output ranges.

Conclusion
Kipp & Zonen pyrheliometers, including the CHP 1 and SHP1, provide high-performance solutions for solar radiation measurement, suitable for various applications in meteorology and renewable energy.