Soil resistivity is a key factor for determining what the resistance of a grounding electrode will be, to what depth it must be driven in order to obtain low earth resistance, and even the type of grounding system that should be designed for this location and facility.
The resistivity of the soil varies widely throughout the world and changes seasonally. Resistivity is strongly affected by the content of electrolytes in the soil, its moisture content, and even its temperature. Soil resistivity measurements are therefore critical for designing and constructing a grounding system appropriate for your site and requirements.
This article describes a simple way to measure soil resistivity known as the Wenner method. Our test instrument will be the AEMC® Ground Tester Model 6472. This instrument automatically calculates and displays soil resistivity, with no manual calculations necessary.
The Model 6472 also features advanced capabilities such as test currents up to 250 milliamps for testing soils with high resistivity, automatic test frequency selection for testing in high EMI environments, and the ability to connect to a computer via AEMC’s DataView® data analysis software.
