The Daystar solar meter measures global solar power in Watts/m2. Readings are instantaneous. The meters are calibrated on clear days in natural sunlight with the plastic protection cover in place. They are pointed directly at the sun and adjusted to the standard*. Meters are designed for use in the field but are not sealed for continuous exposure to weather. No analog output is available. These meters are popular with installers, testers, home-owners, and anyone needing a quick reading of solar power.