AEMC® - 3640 Fall Of Potential Testing - How-To

Grounding is a critical component of electrical systems. Effective grounding provides a low-resistance path for lightning and other phenomena that might otherwise damage electrical systems and injure personnel.

A common method for measuring the resistance of a grounding system is the Fall-of-Potential test, also known as the 3-point or 3-pole test. This involves injecting a current into the ground at a distance from the grounding system under test, and then measuring potential at different points between the grounding system and injector electrode.