Summary
Soil resistivity is the input data that allows grounding to be designed on a real basis. Measuring it correctly avoids poor, oversized or technically hard-to-justify designs.
Wenner method
Wenner uses four equally spaced electrodes. By varying the separation, information is obtained about different apparent soil depths.
It is a widely used method for grounding studies because of its simplicity and traceability.
Schlumberger method
In Schlumberger, the current electrodes are spaced farther apart than the potential electrodes. It can be useful when exploring layers with another field configuration.
The choice depends on the objective, available space and interpretation criteria.
Soil criteria
Soil is rarely homogeneous. For that reason, it is advisable to take several spacings, review data consistency and document visible conditions.
Fills, humidity, paved surfaces and metallic interference can affect measurement quality.
Use in design
The results make it possible to estimate a soil model and calculate grid resistance, potential rise and step and touch voltages.
In substations and medium-voltage projects, this step is key to justify engineering decisions.
Frequently asked questions
Do Wenner and Schlumberger deliver the same result?
They can be close, but they use different geometries and must be interpreted according to the soil model.
Can it be measured on paved ground?
Sometimes it is complex; access, measurement points and data reliability must be evaluated.
How many measurements are needed?
It depends on project size, available geometry and soil variability.
Does resistivity change with the season?
Yes, humidity and temperature can affect the result.
If you need technical support applied to this topic, review our industrial grounding service.