The effects of electrode configuration and design are investigated using a grouped node finite element method (FEM). An estimated expression for an appropriate experimental/actual electrode-angle beta is given for an electrode system modelled with grouped-node FEM or single-node FEM. Analyses and methods for reducing sensor noise are discussed in practical terms. Examples of ERT sensors for different applications are given, which comprise from one to eight sensing planes sized from 6 to 1500 mm in diameter. A novel image reconstruction method based on the sensitivity theorem is presented. The capabilities of ERT and its data interpretation and image processing are discussed for pipelines, hydrocyclones and mixing vessels.