Soil Resistivity Testing: The Wenner Method Explained
Before you install a grounding system, you need to know how conductive the soil is. Soil resistivity testing — using the 4-pole Wenner method — provides that data and drives correct electrode design.
Why Soil Resistivity Matters
Soil resistivity (in ohm-metres) determines how deep rods must go, how many electrodes you need, and where to place them to hit your target ground resistance.
The Wenner Method
Four equally spaced stakes are driven in a straight line; the tester injects current through the outer stakes and measures voltage across the inner pair. The stake spacing sets the depth being assessed — wider spacing tests deeper soil.
Equipment
You need a 4-pole capable earth/soil tester such as the MarMonix MEG825 or MEG925. See the earth resistance tester guide and how to measure earth resistance.