A radiation measuring device for measuring electromagnetic radiation originating from an external source. The radiation measuring device includes, a spectrometer, a pyranometer, a pyrgeometer, a diffuser, and a control unit. The spectrometer and a pyranometer are positioned in a sensor zone of a housing of the radiation measuring device. The spectrometer measures visible shortwave radiation and near-infrared shortwave radiation received at the sensor zone. The pyranometer measures shortwave radiation received at the sensor zone. The pyrgeometer is positioned in another sensor zone of the housing and measures longwave radiation received at the other sensor zone. The control unit receives radiation measurements from the spectrometer, pyranometer, and pyrgeometer. A corrected amount of radiation received at the sensor zones of the radiation measuring device is determined from the received radiation measurements. Other embodiments are described and claimed.