Wenner Four-Pin Soil Resistivity & Corrosivity Calculator
Calculate apparent soil resistivity (ρ in Ω·cm and Ω·m) from Wenner four-pin field resistance measurements and classify soil corrosiveness per ASTM G57 and NACE standards.
Wenner Array Test Parameters
Soil Moisture & Pipeline Context
Apparent Resistivity & Corrosivity
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Frequently Asked Questions
How does the Wenner four-pin array measure soil resistivity?
Four equally spaced metal pins are driven into the ground in a straight line. An alternating current (I) is passed between the two outer pins, and the resulting potential drop (V) is measured across the two inner pins. The apparent soil resistivity is calculated from ρ = 2 · π · a · R.
What is the relationship between pin spacing and measurement depth?
Per the empirical rule of thumb in ASTM G57 and IEEE 81, the depth of soil investigated by the Wenner four-pin method is approximately equal to the pin spacing "a". A spacing of 10 feet measures the average resistivity of the upper 10 feet of soil strata.
How does soil resistivity affect cathodic protection design?
Soil resistivity dictates how easily corrosion currents flow. In low-resistivity soils (< 1,000 Ω·cm), corrosion attacks are rapid and aggressive, but galvanic sacrificial anodes easily deliver protective current. In high-resistivity soils (> 10,000 Ω·cm), galvanic anodes are choked, necessitating high-voltage Impressed Current (ICCP) rectifiers.