Sol-A-Meters are low cost, rugged, weatherproof solar radiometers intended for use under the most severe field conditions. They are completely self-contained and do not require any external power supply. All models incorporate the silicon photovoltaic cell as a sensor. Spectral response is from 0.35 to 1.15 µm. One hundred percent response to a change in signal takes less than one millisecond. All Sol-A-Meters are calibrated for the entire solar spectrum by comparison with thermopile type radiometers in bright sunshine on clear days. Cosine effect and air-mass effect corrections are made during calibration. Standard temperature compensation is from 40 to 140 °F. Each instrument is furnished with a certificate of calibration showing radiation in both English and Metric units.