Calix 500 Series, Руководство пользователя

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As the layers extend outward from the electrode, their surface area becomes larger compared
to the layers nearest the electrode. The resistance of each layer decreases in relation to the
amount of surface area. From a starting point next to the earth electrode, the resistance
measurement to earth will increase with distance. The amount of resistance increase due to
distance will taper off at some point. As the distance from the electrode increases, the
resistance to earth does not increase. As more measurements are taken beyond this point, the
amount of resistance to earth will start to increase again.
The test setup, as illustrated below, uses an Earth Resistance Megger to determine the
resistance of an earth electrode. Grounding system tests are commonly made with a “fall of
potential” test set. Within the test set is an AC current source, a voltage meter, and a number
of test terminal binding posts. The AC voltmeter inside the test set reads out directly in ohms
of resistance. By reading the voltage drop across a current path and applying Ohms Law, the
total resistance of the ground, plus the surface resistance of the earth electrode to the
surrounding ground, can be measured.
AC Voltage
Source
Volt/Ohm
Meter
Test Rod “P”
Test Rod “C”
Earth
5225
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