The Kipp & Zonen CHP1 pyrheliometer uses a thermopile to measure the solar irradiance received from the direction of the sun. It is mounted on a Kipp & Zonen Solys 2 solar tracker to ensure constant pointing in the direction of the sun. It operates in conjunction with pyranometers measuring the total and diffuse solar radiation incident upon a horizontal surface. It is mounted approximately 8 m above ground on the roof of a cabin at the Chilbolton Observatory site.