Irradiance manufactures the RSR2 Rotating Shadowband Radiometer.™ This instrument consists of a silicon photodiode pyranometer and a motor driven band that momentarily shades it from direct sunlight in order to make a measurement. The depth of the shadow and the solar zenith angle can be used to calculate direct normal irradiance (DNI) and diffuse horizontal irradiance (DHI), the two components of sunlight necessary to calculate its effect on non-horizontal surfaces.

Irradiance sells the RSR2 as a package to systems integrators and also assembles custom weather stations including the RSR2 and other sensors.

Calibration services are available for RSR2s and silicon photodiode pyranometers.


Irradiance can provide consulting services related to solar measurements and appreciates unique measurement challenges.


Irradiance, Inc. was founded in 2002 by Edward C. Kern, Jr., Ph.D. to manufacture the Rotating Shadowband Radiometer (RSR2), an instrument Dr. Kern and his colleagues developed in 1991 while Dr. Kern was president of Ascension Technology, Inc. Ascension Technology was a startup company, spin-off from Massachusetts Institute of Technology's early solar photovoltaic power systems research and development projects. During the late 1980's and 1990's the company's focus was on grid-connected PV systems for residential and commercial building roof-top applications. Instrumentation was always a strong component during these early years as most grid-tied systems were then "experimental" in many ways and much needed to be learned about their performance and interconnection to utility grids. Dr. Kern has retired but may be available for special consulting projects.

Dr. Kern's son, Chris Kern, began working with his father in 2012 and took over management of the company in 2016. His prior education and experience includes one summer at Ascension Technology assembling and refurbishing RSRs, a computer science degree, and some time at an Internet company.


Irradiance, Inc. P.O. Box 381374 Cambridge, MA 02238-1374 United States of America
Please email for RMA before shipping equipment.

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