CP 1 – Cathodic Protection Tester Course Manual
© NACE International, 2000
02/01/05
Resistivity is constant for a given material and is computed by the formula:
ρ= R x A
L
Where ρ, Resistivity in Ω-cm
R, Resistance in Ω
A, Cross-Sectional Area in cm
2
L, Length in cm
Using the Wenner method, the soil resistivity is determined by:
ρ=2πaR
Where ρ, resistivity in ohm-cm
a, the spacing of the pins (cm)
R, the resistance measured (Ω)
ρ, resistivity (Ω-cm)
OR
ρ=191.5aR
Where ρ, resistivity in Ω-cm
a, the spacing of the pins (feet)
R, the resistance measured (Ω)
ρ, resistivity (Ω-cm)
Ohm’s Law
E = IR I=E/R R=E/I
To Next Page
Loading...