Getting Down to Earth 55Using the voltage drop and the current through the ground electrode, the resistance of the ground electrode (RG) can be determined.RG = V ÷ IGRG = 0.017 V ÷ 0.004 ARG = 4.25 ΩAs noted, this is a theoretical approach that requires perfect conditions. Any additional current flowing from the service through the ground electrode would reduce the accuracy of the measurement. The earth leakage clamp meter would have to filter out all but the current generated by the instrument through C1 to ensure accuracy. Additionally, this approach requires that a number of mathematical calculations be made.The Attached Rod Technique is based on the theory outlined above. Figure 27 shows an ART test being made.Ground testers that are designed to make ART measurements include a Fig 27: Attached Rod Technique (ART) measurement
