Measuring Ground Resistance | Fluke
When conducting a grounding audit of a central office there are three measurements required. Locate the MGB (Master Ground Bar) to determine the type of grounding system that exists.
Measuring Ground Resistance of Distribution Box
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The Fall-of-Potential Method, also known as the three-point, is a widely used technique for measuring ground resistance. This method involves using a ground tester, which usually consists of three electrodes: a current electrode, a potential (voltage) electrode, and a ground. Specialized earth testers, like the Fluke 1630-2 FC Earth Ground Clamp and the Fluke 1625-2 GEO Earth Ground Tester, are the troubleshooting tools built to make earth ground tests a lot easier. The simplest and somewhat misleading idea of a good ground for an electrical system is a section of iron pipe driven into the earth with a wire conductor connected from the pipe to the electrical circuit (Figure 1). Consequently, ground resistance is generally measured using a square wave or sine wave at a frequency of several dozens of hertz to 1 kHz. Earth resistance (also called ground resistance) is the measure of how easily electric current can flow from a grounding electrode into the surrounding soil.