By varying the distance between the probes a soil resistivity profile can be produced for use in the design of a grounding system. The testing location must be chosen carefully. If the site has multiple soil types or complex geology, several tests may be required. Perform the testing as close as possible to the location where the grounding system will be installed. Avoid testing in areas with overhead wires, buried metallics and areas that have been influenced by salting or fertilizer.
Soil resistivities can range dramatically even on adjacent sites.
As a result, several series of measurements may be required. For sites with high soil resistivity or where a low grounding system resistance target is required you may need to perform additional tests with larger spacings. In general, the more data gathered the more efficient the grounding system design. Inside Grounding Should Be Configured As Single Point Inside grounding involves the electrical bonding of all internal metallics in a building to the outside grounding system. All critical electronic equipment should be configured such that there is only one path to ground.