Yankee Environmental Systems, Inc. Multifilter Rotating Shadowband Radiometer MFR-7

The Multi-Filter Rotating Shadowband Radiometer (Model MFR-7) is a field instrument that simultaneously measures global, diffuse, and direct normal components of spectral solar irradiance. The MFR-7 uses independent interference filter-photodiode combinations, mounted in a temperature-controll ed enclosure, to detect spectral irradiance at six wavelengths and in one broadband channel. An automated, microprocessor-contr olled shadowband is used to alternately shade and then expose the entrance aperture of the instrument, allowing for the measurement of the three solar radiation components. The global and diffuse components are measured directly and the direct-normal component is computed from the difference of the two measured components. The MFR-7 spectral measurements are made at six wavelengths: 415, 500, 615, 673, 870, and 940 nm. The choice of wavelengths allows the reconstruction of the incident solar spectral irradiance and the determination of optical depths of water vapor, aerosols, and ozone (using the Chappuis ozone absorption bands). The broadband channel measures the total solar irradiance, similar to a pyranometer such as our Model TSP-700. Custom wavelength channel configurations are available on special order. The MFR-7's unique ability to make simultaneous spectral measurements of the three solar irradiance components makes it extremely versatile. For example, in order to obtain the data collected in the broadband channel of the MFR-7, at least two instruments would have to be used: a total solar pyranometer, and either a tracker-mounted normal incidence pyrheliometer or a second, shaded total solar pyranometer. The MFR-7 has the advantage of sensing the global and diffuse irradiance components with the same detector. This eliminates the error introduced into the measurement of solar irradiance components by the use of different detectors to measure the different components.