structural features, the presence of dissolved salts, and contaminants, porosity and permeability. There are several basic methods for measuring soil resistance. The measurement is performed with two, three or four electrodes. The measurement methods are: pole-pole, dipole-dipole, pole-dipole, Wenner method, and the Schlumberger method. See also Electrical wiring Ground and neutral Soil resistivity References General IEC 60364-1: Electrical installations of buildings — Part 1: Fundamental principles, assessment of general characteristics, definitions. International Electrotechnical Commission, Geneva. John Whitfield: The Electricians Guide to the 16th Edition IEE Regulations, Section 5.2: Earthing systems, 5th edition. Geoff Cronshaw: Earthing: Your questions answered. IEE Wiring Matters, Autumn 2005. EU Leonardo ENERGY earthing systems education center: Earthing systems resources Dmitry Makarov: What Is a TN-C-S Earthing System? Definition, Meaning, Diagrams. Electric power distribution Electrical wiring Electrical safety IEC 60364