Starting from a parameter estimation problem encountered while interpreting experimental data obtained for the electrodeposition of silver from 1.2-Ag(S2O3)(2)(3-) complexes, an error data analysis more sensitive to mass-transfer controlled phenomena is sought. The key for this adequate analysis is the stochastic contribution to the underlying error structure of impedance data, An experimental assessment of the latter can be achieved by means of an appropriate measurement model (MM) and a set of repeated experiments. In a first section of this paper. it is investigated which influence the independent variable exerts on the ability of a MM to comply with diffusion governed systems. Therefore, a transfer function based measurement model (TMM) is introduced. Second issue is the preconditioning of the electrode, playing a role when sets of repeated measurements are collected.