How to perform the Wenner Four-Electrode Method (ASTM G57)
Here is an explanation how to do the Wenner 4-pin measurement
Significance and Use
Measurement of soil resistivity is used for the control of corrosion of buried structures. Soil resistivity is used both for the estimation of expected corrosion rates and for the design of cathodic protection systems. As an essential design parameter for cathodic protection systems, it is important to take as many measurements as necessary so as to get a sufficiently representative characterization of the soil environment that the entire buried structure will experience.
1.1 This test method covers the equipment and procedures for the field measurement of soil resistivity, both in situ and for samples removed from the ground, for use in the control of corrosion of buried structures.
1.2 To convert cm (metric unit) to metre (SI unit), divide by 100.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.