What is the difference between Wenner and Schlumberger method?
Schlumberger is the best method used for vertical electrical sounding for practical reasons. It is less labor-intensive than the Wenner array (see below) because you only need to move the two transmitting electrodes for each new reading, whereas the Wenner requires moving all four electrodes for each new measurement.
What is Schlumberger method?
The Schlumberger method was developed to increase the voltage signal for the earlier, less sensitive instruments, by placing the potential probes closer to the current probes. The soil resistivity measurements will be affected by existing nearby grounded electrodes.
What is meant by Wenner configuration in geology?
2.2 Wenner-Schlumberger configuration Wenner-Schlumberger configuration is a configuration with a constant system of spacing rules with a note of factor “n” as this configuration is the comparison of the distance between C1-P1 (or C2-P2) electrodes with spaces between P1-P2 as in figure 3.
What is the resistivity of sand?
200 – 300
Types of soil and their mean value of resistivities
| Soil | Mean Value of Resistivity (ohm m, Ω m) |
|---|---|
| Sandstone | 1500 – 10000 |
| Sandstone, modified | 100 – 600 |
| Shist, shale | 50 – 300 |
| Siliceous sand | 200 – 300 |
What is resistivity profiling?
Electrical resistivity profiling is simply a two-dimensional resistivity method, where an image representing a slice of the earth is created and electrical property contrasts are used to interpret differing geological or hydrogeological conditions. We use color contouring to visually identify these conditions.
How do you test for earth resistivity?
To test soil resistivity, connect the ground tester as shown below. As you can see, four earth ground stakes are positioned in the soil in a straight line, equidistant from one another. The distance between earth ground stakes should be at least three times greater than the stake depth.
How many types of resistivity are there?
The three main methods of electric resistivity surveys are vertical electric sounding (VES), electric profiling, and electric imaging. Each of these utilize one of the array configurations mentioned above.
What is the purpose of resistivity test?
Soil resistivity testing is the process of measuring a volume of soil to determine the conductivity of the soil. The resulting soil resistivity is expressed in ohm-meter or ohm-centimeter. Soil resistivity testing is the single most critical factor in electrical grounding design.
What is the difference between soil resistivity and earth resistance?
The earth resistance mainly implies the resistance between the electrode and the point of zero potential. The flow of current into the grounds depends on the resistivity of the soil in which the earth electrode is placed. The resistivity of the soil may vary from 1 to 1000 ohm-m depends on the nature of the soil.
How is soil resistivity measured by Wenner and Schlumberger?
In any cases, for both Wenner and Schlumberger methods the electrode spacing between the currents probe corresponds to the depth of soil investigation and the measured apparent soil resistivity is referred to a soil volume as in the figure.
Which is more economical Wenner 4 or Schlumberger array?
Schlumberger Array. The soil resistivity testing method Schlumberger Array is more economical than the Wenner 4 Probe Test when it comes to the man power required to perform the task. The outer electrode can be moved four or five times for each move of the inner electrode [2].
What are the electrodes in the Schlumberger array?
The Schlumberger array is an array where four electrodes are placed in line around a common midpoint. The two outer electrodes, A and B, are current electrodes, and the two inner electrodes, M and N, are potential electrodes placed close together.
How is the Schlumberger array used for profiling?
The Schlumberger array is also used for mapping or profiling for lateral resistivity changes. The typical profiling is done by larger fixed AB current electrode pairs and moving MN potential electrode pairs between them.