AEMC 6422 User Manual page 22

2.3.1.2 Measuring Resistance of Ground Electrodes (62% Method)
The 62% method the most accurate method but is limited by the fact that the
ground tested is a single unit. This method applies only when all three electrodes
are in a straight line and the ground is a single electrode, pipe, or plate, etc., as
shown below.
Consider the illustration below, which shows the effective resistance areas
(concentric shells) of the ground electrode E and of the auxiliary current
electrode H. The resistance areas overlap.
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Ground Tester Models 6422/6424