Measuring Sunlight: The Pyranometer

Scientists and meteorologists study many aspects of the atmosphere. While thermometers measure heat and barometers measure air pressure, scientists also use a tool to measure the intensity of sunlight. Sunlight does not fall evenly across the Earth’s surface.

A pyranometer is a device that measures how much sunlight falls on the ground per square meter every second. There are two main types:

1. One measures sunlight based on the amount of heat generated.

2. The other measures it based on how much electricity a solar cell produces.

A standard pyranometer has two black carbon disks inside a glass cover. One disk is placed in the sun, and the other is kept in the shade nearby. This creates a temperature difference (one stays hot, the other cool). By measuring the electric current produced by these two disks, the amount of sunlight is determined. While the method sounds simple, the actual design and calculations are complex.