Kelvin probe force spectroscopy (KPFS) and finite-element method (FEM) simulations were employed to investigate the averaging effect of the work function signals of nanoscale potential distributions in Kelvin probe force microscopy (KPFM). A KPFS routine is presented that enables meaningful experimental results even for electronically inhomogeneous KPFM tips. By use of this routine a strong distance dependence of the averaging effect is revealed. A combination of KPFS experiments and FEM simulations is applied to quantify the averaging effect, which simplifies comparison among different experiments and to theory. No influence of surface topography on the averaging effect was observed.
