An in-process measurement apparatus can be used to determine characteristics of a photovoltaic module. Capacitance measurements of the photovoltaic module are conducted before, during, or after execution of a high-potential leakage test, a performance test, or other tests of the module. The capacitance measurements are used to determine the characteristics of the photovoltaic module, including information regarding depletion width, doping density, film layer thickness, trap concentrations and absorber thickness. The apparatus can also be used to ensure that photovoltaic modules conform to product specifications.