Earth electrode resistance testing

The method to carrying out this test.

1) Using a proprietary tester.

The test unit has three connections. The first is attached to the electrode under test, the second to an auxiliary potential electrode or ‘spike’, and the third to an auxiliary current electrode.

The positioning of the auxiliary electrodes is critical to the test and positioning is dependant upon the length of the electrode under test. The current electrode is placed at a distance ten times the test electrodes length and the potential electrode is placed in a direct line midway between the two. At this point a reading is taken and noted. Two further readings are now taken. The first with the potential electrode placed 10% nearer the current electrode and the second, with the potential electrode placed 10% nearer the electrode under test (from its original position).

The average of the three readings is taken as the electrodes resistance (as long as all three readings are within 5% of one another). If they exceed 5% the test must be repeated with the distance of test and auxiliary electrodes increased.

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