FieldengCathodic Protection
Wenner Apparent Resistivity
Apparent soil resistivity from a Wenner four-pin measurement.
Cathodic Protection
Apparent soil resistivity from a Wenner four-pin measurement.
App id: SOIL-01. Reference version 1.0.
How to fill it
Fill the inputs. The tool shows the outputs.
On the tool screen, Calc is the working sheet. Presets stores values you reuse. Reference is the formula, assumptions, and provenance below.
Formula
ρ = 2π a RInputs
| Name | Unit |
|---|---|
| Electrode spacing | ft |
| Measured resistance (camera) | ohm |
Outputs
| Name | Unit |
|---|---|
| Apparent resistivity (hero result) | ohm-cm |
Diagnose
Observations are context. They do not pass or fail a structure. See Diagnose.
Screening bands in the app: Very Low · Low · Moderate · High · Very High.
| When | Observation | Severity |
|---|---|---|
resistivity < 1,000 Ω·cm | Very Low | info |
1,000 ≤ resistivity < 3,000 Ω·cm | Low | info |
3,000 ≤ resistivity < 10,000 Ω·cm | Moderate | info |
10,000 ≤ resistivity < 30,000 Ω·cm | High | info |
resistivity ≥ 30,000 Ω·cm | Very High | info |
Assumptions
- Result is apparent resistivity, not a homogeneous-soil truth.
- Equal pin spacing (standard Wenner geometry).
Provenance
- NACE/AMPP CP training material.
- CP4 exam preparation guide.
- Megger soil-resistivity technical note.