When using a four- terminal earth tester, the P1 and C1 terminals connect to the ground rod under test; the P2 and C2 terminals connect to an all-metallic water-pipe system. If you are using a three-terminal test set, connect the X terminal to the ground rod under test; P and Cterminals to the pipe system. If the water system is extensive (covering a large area), its resistance should only be a fraction of an ohm and will not influence the test results. You can then take the instrument reading as being the resistance of the ground rod under test.
The direct method is the simplest way to make an earth resistance test. With this method, resistance of two electrodes in series is measured – the driven rod and the water system. But there are three important limitations:
1. The water pipe system must be extensive enough to have a negligible resistance.
2. The water pipe system must be metallic throughout, without any insulating couplings or flanges.
3. The earth electrode under test must be far enough away from the water-pipe system to be outside its sphere of influence.
When you need to conduct earth resistance tests, let Protec Equipment Resources assist. We can either rent or sell you a quality test sets from Megger or AEMC. Our experienced staff will always set you up with the right tools. Do not hesitate to call us at 1-866-352-5550 for assistance.