The solar energy illuminating a module or array is influenced by several factors. Angle of incidence, atmospheric dust and moisture, cloud cover, nearby reflective surfaces all contribute to the true solar energy incident on the solar array. Since solar modules and arrays are seldom irradiated by the standard 1000 W/m2 by which they are rated, a reference cell is required to calculate the correction. The Reference Cell can be used for the evaluation of solar module and array performance under off angle illumination and hazy sky conditions.

The Reference Cell is made of a multi-crystal silicon solar cell housed in a rugged metal case and connects to standard hand held meters via banana jacks. The reference cell is calibrated to produce a specified mV reading at 1000 watts per square meter (1000W/m2) or defined as (1) sun illumination.