Apogee offers two types of pyranometers: our original silicon-cell models and our new line of thermopile pyranometers. Both products are now ISO 9060:2018 Class C rated (previously known as second class). Silicon-cell solar radiation sensor models are excellent for applications that do not require the higher accuracy and cost of a thermopile pyranometer. They are less expensive and have a faster response time, but they have higher errors under cloudy conditions. Our new cost-effective thermopile pyranometers feature a blackbody thermopile detector, which provides a much broader and more uniform spectral response for better performance in all atmospheric conditions.