Pyranometer Sensors and Meters

Pyranometer sensors measure the shortwave radiation reaching the Earth's surface, measured in Joules m^-2 s^-1 or Watts m^-2.

Cosine Response

A cosine corrected pyranometer sensor is designed to maintain its accuracy when radiation comes from different angles. For pyranometers, the test of cosine response is to measure extreme zenith angles. The cosine response of Model MP-200 at 75° is ± 4 percent, see diagram at right and graph below. Zenith angles greater than 75° contribute less than 3 percent of daily radiation. The ideal cosine response in a vacuum is shown in red in the graph below. The CM21 and Apogee MP-200 deviate from the ideal due to humidity and particulate matter in the atmosphere.