The contact free vibrating capacitor method is a valuable tool for investigating the surface potentials of solid surfaces. The purpose of the present article is to summarize the theory and capabilities of the vibrating capacitor method, especially scanning vibrating capacitor pictures in the MEMS testing. After a brief review some results will be discussed, such as equilibrium and non-equilibrium surface potential maps taken from a MEMS resonator, a surface potential map from a cantilever testchip and some maps from a radial-channel micro-cooler plate and heat flux meter. Potential maps contain a lot of information concerning the surface conditions, included the inhomogeneities of the technology, static surface charge, bias and effects of other additional excitations. These potential maps may help in the development, quality control and defect analysis of the MEMS.