AEMC 4500 User Manual

28 Digital Ground Resistance Tester Model 4500either side of the initial Y setting are most likely to be within the establishedtolerance band. This tolerance band is defined by the user and expressedas a percent of the initial reading: ± 2%, ± 5%, ± 10%, etc.ResistanceDistance from Y to Ground ElectrodeEffectiveResistanceAreas DoNot OverlapX Y ZGroundElectrodeUnder TestAuxiliaryPotentialElectrodeAuxiliaryCurrentElectrodeD62% of DResistance ofAuxiliary CurrentElectrodeResistance of Earth ElectrodeFigure 144.4.1 Auxiliary Electrode SpacingNo definite distance between X and Z can be given, since this distance isrelative to the diameter of the electrode tested, its length, the homogeneityof the soil tested, and particularly, the effective resistance areas. However,an approximate distance may be determined from the following chartwhich is given for a homogeneous soil and an electrode of 1" in diameter.(For a diameter of 1/2", reduce the distance by 10%; for a diameter of 2"increase the distance by 10%.)Approximate distance to auxiliary electrodes using the 62% method:Depth Driven Distance to Y Distance to Z6 ft. 45 ft. 72 ft.8 ft. 50 ft. 80 ft.10 ft. 55 ft. 88 ft.12 ft. 60 ft. 96 ft.18 ft. 71 ft. 115 ft.20 ft. 74 ft. 120 ft.30 ft. 86 ft. 140 ft.