Soil Resistivity Measurements (Ρ Position) - AEMC 6470 User Manual

4.7 Soil Resistivity Measurements
Soil Resistivity is measured using the resistance measurement R
tances between the measurement rods.
Two measurement methods are possible:
• Wenner method
• Schlumberger
To plot the resistivity profile as a function of the depth of the earth, the Schlumberg-
er method is easier to implement as only the two center rods need to be moved.
With the Wenner method, the four rods need to be moved and are equally spaced.
This is the more common method used for measuring soil resistivity before install-
ing grounds. Schlumberger, which is also a good method, also uses 4 rods but only
the two center rods are moved.
NOTE: That the two center auxiliary rods are the current electrodes, and their
spacing corresponds to the depth of the resistivity measured.
A four-electrode piece of equipment, which can be made available in the physics
laboratory, was designed and fabricated for measuring current and potential val-
ues so as to obtain the resistivity values. Readings taken from our chosen location
using both Wenner and Schlumberger arrays were analyzed.
In the resistivity method, the Wenner configuration discriminates between resistivi-
ties of different geoelectric lateral layers, while the Schlumberger configuration is
used for the 'depth sounding'. The theory behind the resistivity method was intro-
duced with some degree of sophistication. Experimentally determined values of
depth to surface were correlated with the values determined from the excavated
site and this gave a good correlation.
It was observed that the resistivity value in the chosen location increases with the
depth and the Schlumberger method was seen to have a greater penetration than
the Wenner.
Shop for AEMC products online at:
Ground Resistance Tester Model 6470
method
ShopAEMC
www.
ρ
( Position)
.ca 1.877.766.5412
and dis-
S-ES
45