SR15 digital pyranometer series is an all-digital range of solar radiation sensors applied in general high-accuracy observations. SR15 pyranometers comply with the “first class” specifications according to the ISO 9060:1990 standard and “spectrally flat class B” requirements in the 2018 revision. Version SR15-D2A2 offers Modbus over TTL, and 4–20 mA current loop output.