Pyranometers are radiometers designed for measurement of the solar irradiance on a plane surface, normally from solar radiation and lamps. Pyranometer sometimes called a solarimeter, which is used to measure broadband solar irradiance on a planar surface and is a sensor that is designed to measure the solar radiation flux density in W/m2 (watts per metre square) from a field of view of 180 degrees.

Not all of the solar energy reaching Earth’s outer atmosphere reaches the surface of the Earth. Some of this energy is reflected back out into space and some of it is absorbed in the atmosphere itself. Pyranometer instrument can be used for measuring solar radiation received from a whole hemisphere. It is suitable for measuring global sun plus sky radiation. Solar radiation varies significantly among regions. Season and time of day are major considerations, but surrounding terrain elevation, man-made obstructions, and surrounding trees can also cause large variations in locations with a small area. Often, the required measurement is energy flux density of both direct beam and diffuse sky radiation passing through a horizontal plane of known unit area (i.e., global sun plus sky radiation). On a typical summer day at midday in temperate latitudes, about 1000 W/m2 actually reaches Earth’s surface. This is a quite a lot of energy, enough to power 10×100 Watt light bulbs.

Modern digital pyranometers are used for recording solar radiation (shortwave) for a spectral response graph. Measurements can be automatically stored in computer system memory using USB/RS232/Ethernet interfaces. Also, it is possible to control the operation of pyranometers using software applications from computer. And some portable wireless remote pyranometers can transmit the measured solar radiation data using GSM mobile communication.

A typical pyranometer does not require any power to operate and are frequently used in meteorological research, solar energy research, material testing, climate control in greenhouses, building physics, science and many other applications. They can be seen in many meteorological stations, often installed horizontally and next to solar panels, and the sensor is mounted in the surface plane of the panel. The pyranometer has a glass dome shaded from the Sun’s beam and the shading is accomplished either by an occulting (concealing) disc or a shading arm.

Pyrheliometer for Solar Irradiance Measurement

Pyrheliometer is an instrument for direct measurement of direct beam solar irradiance. Sunlight enters the instrument through a window and is directed onto a thermopile which converts heat to an electrical signal that can be recorded. The signal voltage is converted via a formula to measure watts per square meter.

Typical pyrheliometer measurement applications include scientific meteorological and climate observations, material testing research, and assessment of the efficiency of solar collectors and photovoltaic devices. It is used with a solar tracking system to keep the instrument aimed at the sun. A pyrheliometer is often used in the same setup with a pyranometer.