Installation Guide

Table Of Contents
Using a Clamp-On Ground Resistance Tester
1. Clamp the tester around the ground conductor and read the resistance-to-ground directly
from a digital display.
This type of measurement permits the quality of the grounding connections and bonding to
be verified.
2. Use certified Ground Resistance Testers for all clamp-on ground resistance measurements.
Principle of Operation
In a typical grounded system, the neutral is bonded to ground at the service panel. There are
numerous neutral-to-ground bonds prior to this point, all in parallel. These bonds create an
effective earth resistance from the utility of virtually zero. A clamp-on ground resistance tester
uses this fact along with the connection between the utility service and the grounding system
under test. The clamp-on tester injects a known voltage into the system and measures the
current felt on the return path. Realizing the near "zero" resistance on the service side, the meter
reading indicates the resistance of the grounding system under test.
The following illustration shows a Principle of Operation.
23 June 2020 TDC-0971-012 Itron, Inc. Page 130 of 134
CCU 100 and Repeater 100 Installation Guide F Grounding Specifications